Update README.md

README.md

@@ -70,12 +70,24 @@ Commands:
     	Image height (default "0")
     --fit
     	Best fit for required width and height (default "false")
+    --dpi
+    	Document rendering resolution in DPI (PDF, EPUB, etc.), 0 uses the default (300) (default "0")
     --format
     	Image format, valid values are jpeg, png, tiff, bmp, webp, avif, jxl (default "jpeg")
     --archive
     	Archive format, valid values are zip, tar (default "zip")
+    --zip-level
+    	ZIP compression level, 0 disables compression, 1-9 sets deflate level (1 fastest, 9 smallest), -1 uses the default (default "-1")
     --quality
     	Image quality (default "75")
+    --effort
+    	Encoder speed/effort, format-specific (webp method 0-6, avif speed 0-10, jxl effort 1-10), -1 uses the format default (default "-1")
+    --lossless
+    	Lossless compression (webp, avif, jxl), ignores quality (default "false")
+    --combine
+    	Combine all inputs into a single archive (default "false")
+    --outfile
+    	Output file name for --combine (default: first input + -combined) (default "")
     --filter
     	0=NearestNeighbor, 1=Box, 2=Linear, 3=MitchellNetravali, 4=CatmullRom, 6=Gaussian, 7=Lanczos (default "2")
     --no-cover
@@ -114,10 +126,16 @@ Commands:
     	Image height (default "0")
     --fit
     	Best fit for required width and height (default "false")
+    --dpi
+    	Document rendering resolution in DPI (PDF, EPUB, etc.), 0 uses the default (300) (default "0")
     --format
     	Image format, valid values are jpeg, png, tiff, bmp, webp, avif (default "jpeg")
     --quality
     	Image quality (default "75")
+    --effort
+    	Encoder speed/effort, format-specific (webp method 0-6, avif speed 0-10, jxl effort 1-10), -1 uses the format default (default "-1")
+    --lossless
+    	Lossless compression (webp, avif, jxl), ignores quality (default "false")
     --filter
     	0=NearestNeighbor, 1=Box, 2=Linear, 3=MitchellNetravali, 4=CatmullRom, 6=Gaussian, 7=Lanczos (default "2")
     --outdir
@@ -138,6 +156,8 @@ Commands:
     	Image height (default "0")
     --fit
     	Best fit for required width and height (default "false")
+    --dpi
+    	Document rendering resolution in DPI (PDF, EPUB, etc.), 0 uses the default (300) (default "0")
     --filter
     	0=NearestNeighbor, 1=Box, 2=Linear, 3=MitchellNetravali, 4=CatmullRom, 6=Gaussian, 7=Lanczos (default "2")
     --outdir
@@ -189,6 +209,10 @@ Commands:
 
 `cbconvert --format avif --quality 50 --width 1280 --outdir ~/comics /media/comics/Misc/`
 
+* Combine several issues into a single archive:
+
+`cbconvert convert --combine --outfile Series.cbz --outdir ~/comics issue1.cbz issue2.cbr issue3.cb7`
+
 ### Quality settings
 
 This table maps quality settings for JPEG to the respective AVIF and WEBP quality settings:

cbconvert.go

@@ -39,6 +39,8 @@ type Options struct {
 	Height int
 	// Best fit for required width and height
 	Fit bool
+	// Document rendering resolution in DPI (PDF, EPUB, etc.); 0 uses the default
+	DPI int
 	// 0=NearestNeighbor, 1=Box, 2=Linear, 3=MitchellNetravali, 4=CatmullRom, 6=Gaussian, 7=Lanczos
 	Filter int
 	// Do not convert the cover image
@@ -178,6 +180,7 @@ func (o Options) Args() []string {
 	num("width", o.Width, def.Width)
 	num("height", o.Height, def.Height)
 	flag("fit", o.Fit)
+	num("dpi", o.DPI, def.DPI)
 	str("format", o.Format, def.Format)
 	str("archive", o.Archive, def.Archive)
 	num("zip-level", o.ZipLevel, def.ZipLevel)
@@ -203,6 +206,15 @@ func (o Options) Args() []string {
 	return args
 }
 
+// renderDPI returns the document rendering resolution, falling back to 300 when unset.
+func (c *Converter) renderDPI() float64 {
+	if c.Opts.DPI > 0 {
+		return float64(c.Opts.DPI)
+	}
+
+	return 300
+}
+
 // Cancel cancels the operation.
 func (c *Converter) Cancel() {
 	if c.OnCancel != nil {

cbconvert_convert.go

@@ -48,7 +48,7 @@ func (c *Converter) convertDocument(ctx context.Context, fileName string) error
 			return fmt.Errorf("convertDocument: %w", ctx.Err())
 		}
 
-		img, err := doc.Image(n)
+		img, err := doc.ImageDPI(n, c.renderDPI())
 		if err != nil {
 			return fmt.Errorf("convertDocument: %w", err)
 		}

cbconvert_cover.go

@@ -52,7 +52,7 @@ func (c *Converter) coverDocument(fileName string) (image.Image, error) {
 	}
 	defer doc.Close()
 
-	img, err := doc.Image(0)
+	img, err := doc.ImageDPI(0, c.renderDPI())
 	if err != nil {
 		return nil, fmt.Errorf("coverDocument: %w", err)
 	}

cbconvert_test.go

@@ -114,16 +114,52 @@ func TestArgs(t *testing.T) {
 	opts.Effort = 4
 	opts.Lossless = true
 	opts.Width = 1200
+	opts.DPI = 150
 	opts.Grayscale = true
 	opts.OutDir = "/out"
 
 	got := strings.Join(opts.Args(), " ")
-	want := "--width 1200 --format webp --quality 90 --effort 4 --lossless --grayscale --outdir /out"
+	want := "--width 1200 --dpi 150 --format webp --quality 90 --effort 4 --lossless --grayscale --outdir /out"
 	if got != want {
 		t.Errorf("Args() = %q, want %q", got, want)
 	}
 }
 
+func TestConvertDPI(t *testing.T) {
+	tmpDir, err := os.MkdirTemp(os.TempDir(), "cbc")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	dims := func(dpi int) int {
+		opts := NewOptions()
+		opts.OutDir = tmpDir
+		opts.DPI = dpi
+
+		conv := New(opts)
+
+		files, err := conv.Files([]string{"testdata/test.pdf"})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		for _, file := range files {
+			if err := conv.Convert(file); err != nil {
+				t.Fatal(err)
+			}
+		}
+
+		return firstPage(t, conv, filepath.Join(tmpDir, "test.cbz")).Bounds().Dx()
+	}
+
+	low := dims(150)
+	high := dims(600)
+	if low >= high {
+		t.Errorf("higher DPI should render larger pages: 150dpi=%d, 600dpi=%d", low, high)
+	}
+}
+
 func TestConvertResize(t *testing.T) {
 	tmpDir, err := os.MkdirTemp(os.TempDir(), "cbc")
 	if err != nil {

cmd/cbconvert-gui/dialogs.go

@@ -0,0 +1,80 @@
+package main
+
+import "github.com/gen2brain/iup-go/iup"
+
+func fileDlg(title string, multiple, directory bool, dirKey string) ([]string, error) {
+	ret := make([]string, 0)
+
+	dlg := iup.FileDlg()
+	defer dlg.Destroy()
+
+	if !directory {
+		mf := "YES"
+		if !multiple {
+			mf = "NO"
+		}
+
+		dlg.SetAttributes(map[string]string{
+			"DIALOGTYPE":     "OPEN",
+			"MULTIPLEFILES":  mf,
+			"MULTIVALUEPATH": "YES",
+			"EXTFILTER":      "Comic Files|*.rar;*.zip;*.7z;*.tar;*.cbr;*.cbz;*.cb7;*.cbt;*.pdf;*.epub;*.mobi;*.docx;*.pptx|",
+			"FILTER":         "*.cb*", // for Motif
+			"TITLE":          title,
+		})
+	} else {
+		dlg.SetAttributes(map[string]string{
+			"DIALOGTYPE": "DIR",
+			"TITLE":      title,
+		})
+	}
+
+	setStartDir(dlg, dirKey)
+
+	iup.Popup(dlg, iup.CENTERPARENT, iup.CENTERPARENT)
+
+	if dlg.GetInt("STATUS") == 0 {
+		switch {
+		case multiple:
+			// MULTIVALUEPATH makes each MULTIVALUE a full path (id 0 is the path), so a folder-spanning selection works.
+			count := dlg.GetInt("MULTIVALUECOUNT")
+			if count > 1 {
+				for i := 1; i < count; i++ {
+					ret = append(ret, iup.GetAttributeId(dlg, "MULTIVALUE", i))
+				}
+			} else if value := dlg.GetAttribute("VALUE"); value != "" {
+				ret = append(ret, value)
+			}
+		default:
+			ret = append(ret, dlg.GetAttribute("VALUE"))
+		}
+
+		rememberDir(dlg, dirKey)
+	}
+
+	return ret, nil
+}
+
+func saveDlg(title, dirKey string) string {
+	dlg := iup.FileDlg()
+	defer dlg.Destroy()
+
+	dlg.SetAttributes(map[string]string{
+		"DIALOGTYPE": "SAVE",
+		"EXTFILTER":  "Comic Files|*.cbz;*.cbt|",
+		"FILTER":     "*.cb*", // for Motif
+		"TITLE":      title,
+	})
+
+	setStartDir(dlg, dirKey)
+
+	iup.Popup(dlg, iup.CENTERPARENT, iup.CENTERPARENT)
+
+	if dlg.GetInt("STATUS") == -1 {
+		return ""
+	}
+
+	rememberDir(dlg, dirKey)
+
+	return dlg.GetAttribute("VALUE")
+}

cmd/cbconvert-gui/handlers.go

@@ -0,0 +1,442 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"slices"
+	"strconv"
+	"strings"
+
+	"github.com/gen2brain/cbconvert"
+	"github.com/gen2brain/iup-go/iup"
+)
+
+// selectRow focuses and selects the given 0-based row in the table.
+func selectRow(i int) {
+	if i < 0 || i >= len(files) {
+		return
+	}
+
+	index = i
+	iup.GetHandle("Table").SetAttribute("FOCUSCELL", fmt.Sprintf("%d:1", i+1))
+}
+
+// onSort re-syncs the files slice to the table's displayed order after a sort, so rows keep mapping to the right file.
+func onSort(ih iup.Ihandle, col int) int {
+	n := len(files)
+	if n < 2 {
+		return iup.DEFAULT
+	}
+
+	rowKey := func(name, size string) string {
+		return name + "\x00" + size
+	}
+
+	buckets := make(map[string][]int, n)
+	for i, f := range files {
+		size := strconv.FormatFloat(float64(f.Stat.Size())/(1024*1024), 'f', 2, 64)
+		k := rowKey(f.Name, size)
+		buckets[k] = append(buckets[k], i)
+	}
+
+	var selPath string
+	if index >= 0 && index < len(files) {
+		selPath = files[index].Path
+	}
+
+	reordered := make([]cbconvert.File, 0, n)
+	for lin := 1; lin <= n; lin++ {
+		k := rowKey(iup.GetAttributeId2(ih, "", lin, 1), iup.GetAttributeId2(ih, "", lin, 3))
+		idxs := buckets[k]
+		if len(idxs) == 0 {
+			return iup.DEFAULT
+		}
+		reordered = append(reordered, files[idxs[0]])
+		buckets[k] = idxs[1:]
+	}
+
+	files = reordered
+
+	index = -1
+	if selPath != "" {
+		for i, f := range files {
+			if f.Path == selPath {
+				selectRow(i)
+				break
+			}
+		}
+	}
+
+	return iup.DEFAULT
+}
+
+// appendFile adds a file as a new row to the table and the files slice.
+func appendFile(file cbconvert.File) {
+	files = append(files, file)
+
+	t := iup.GetHandle("Table")
+	lin := len(files)
+	t.SetAttribute("NUMLIN", strconv.Itoa(lin))
+	iup.SetAttributeId2(t, "", lin, 1, file.Name)
+	iup.SetAttributeId2(t, "", lin, 2, cbconvert.FileType(file.Path))
+	iup.SetAttributeId2(t, "", lin, 3, strconv.FormatFloat(float64(file.Stat.Size())/(1024*1024), 'f', 2, 64))
+}
+
+func previewPost() {
+	if index == -1 || len(files) == 0 {
+		return
+	}
+
+	width, height := previewSize()
+	iup.GetHandle("Loading").SetAttributes("VISIBLE=YES, START=YES")
+	if strings.ToLower(iup.GetGlobal("DRIVER")) == "motif" {
+		iup.GetHandle("Preview").SetAttribute("IMAGE", "")
+	}
+
+	opts := options()
+
+	go func(opts cbconvert.Options) {
+		conv := cbconvert.New(opts)
+
+		var s string
+		file := files[index]
+
+		img, err := conv.Preview(file.Path, file.Stat, width, height)
+		if err != nil {
+			s = err.Error()
+			fmt.Println(err)
+		}
+
+		iup.PostMessage(iup.GetHandle("Preview"), s, 0, img)
+	}(opts)
+}
+
+func onAddFiles(ih iup.Ihandle) int {
+	args, err := fileDlg("Add Files", true, false, inputDirKey)
+	if err != nil {
+		iup.PostMessage(iup.GetHandle("dlg"), err.Error(), 0, 0)
+		fmt.Println(err)
+
+		return iup.DEFAULT
+	}
+
+	if len(args) > 0 {
+		conv := cbconvert.New(options())
+
+		fs, err := conv.Files(args)
+		if err != nil {
+			iup.PostMessage(iup.GetHandle("dlg"), err.Error(), 0, 0)
+			fmt.Println(err)
+
+			return iup.DEFAULT
+		}
+
+		wasEmpty := len(files) == 0
+
+		for _, file := range fs {
+			appendFile(file)
+		}
+
+		if wasEmpty && len(files) > 0 {
+			selectRow(0)
+		}
+
+		setActive()
+
+		if wasEmpty {
+			previewPost()
+		}
+	}
+
+	return iup.DEFAULT
+}
+
+func onAddDir(ih iup.Ihandle) int {
+	args, err := fileDlg("Add Directory", false, true, inputDirKey)
+	if err != nil {
+		iup.PostMessage(iup.GetHandle("dlg"), err.Error(), 0, 0)
+		fmt.Println(err)
+
+		return iup.DEFAULT
+	}
+
+	if len(args) > 0 {
+		conv := cbconvert.New(options())
+
+		fs, err := conv.Files(args)
+		if err != nil {
+			iup.PostMessage(iup.GetHandle("dlg"), err.Error(), 0, 0)
+			fmt.Println(err)
+
+			return iup.DEFAULT
+		}
+
+		wasEmpty := len(files) == 0
+
+		for _, file := range fs {
+			appendFile(file)
+		}
+
+		if wasEmpty && len(files) > 0 {
+			selectRow(0)
+		}
+
+		setActive()
+
+		if wasEmpty {
+			previewPost()
+		}
+	}
+
+	return iup.DEFAULT
+}
+
+func onRemove(ih iup.Ihandle) int {
+	if index < 0 || index >= len(files) {
+		return iup.IGNORE
+	}
+
+	iup.GetHandle("Table").SetAttribute("DELLIN", strconv.Itoa(index+1))
+	files = slices.Delete(files, index, index+1)
+
+	if index >= len(files) {
+		index = len(files) - 1
+	}
+
+	setActive()
+	previewPost()
+
+	return iup.DEFAULT
+}
+
+func onRemoveAll(ih iup.Ihandle) int {
+	index = -1
+	files = make([]cbconvert.File, 0)
+
+	iup.GetHandle("Table").SetAttribute("NUMLIN", "0")
+	setActive()
+
+	return iup.DEFAULT
+}
+
+func onThumbnail(ih iup.Ihandle) int {
+	conv := cbconvert.New(options())
+	conv.Nfiles = len(files)
+	activeConv = conv
+	setBusy(true)
+
+	conv.OnProgress = func() {
+		iup.PostMessage(iup.GetHandle("ProgressBar"), "progress2", 0, conv)
+	}
+
+	var canceled = false
+	conv.OnCancel = func() {
+		canceled = true
+	}
+
+	iup.GetHandle("dlg").SetCallback("K_ANY", iup.KAnyFunc(func(ih iup.Ihandle, c int) int {
+		if c == iup.K_ESC {
+			conv.Cancel()
+		}
+
+		return iup.DEFAULT
+	}))
+
+	iup.PostMessage(iup.GetHandle("ProgressBar"), "start", 0, conv)
+
+	go func(c *cbconvert.Converter) {
+		for _, file := range files {
+			if canceled {
+				break
+			}
+
+			if err := c.Thumbnail(file); err != nil {
+				iup.PostMessage(iup.GetHandle("dlg"), err.Error(), 0, 0)
+				fmt.Println(err)
+
+				continue
+			}
+		}
+
+		iup.PostMessage(iup.GetHandle("ProgressBar"), "finish", 0, 0)
+	}(conv)
+
+	return iup.DEFAULT
+}
+
+func onCover(ih iup.Ihandle) int {
+	conv := cbconvert.New(options())
+	conv.Nfiles = len(files)
+	activeConv = conv
+	setBusy(true)
+
+	conv.OnProgress = func() {
+		iup.PostMessage(iup.GetHandle("ProgressBar"), "progress2", 0, conv)
+	}
+
+	var canceled = false
+	conv.OnCancel = func() {
+		canceled = true
+	}
+
+	iup.GetHandle("dlg").SetCallback("K_ANY", iup.KAnyFunc(func(ih iup.Ihandle, c int) int {
+		if c == iup.K_ESC {
+			conv.Cancel()
+		}
+
+		return iup.DEFAULT
+	}))
+
+	iup.PostMessage(iup.GetHandle("ProgressBar"), "start", 0, conv)
+
+	go func(c *cbconvert.Converter) {
+		for _, file := range files {
+			if canceled {
+				break
+			}
+
+			if err := c.Cover(file); err != nil {
+				iup.PostMessage(iup.GetHandle("dlg"), err.Error(), 0, 0)
+				fmt.Println(err)
+
+				continue
+			}
+		}
+
+		iup.PostMessage(iup.GetHandle("ProgressBar"), "finish", 0, 0)
+	}(conv)
+
+	return iup.DEFAULT
+}
+
+func onConvert(ih iup.Ihandle) int {
+	if busy {
+		if activeConv != nil {
+			activeConv.Cancel()
+		}
+
+		return iup.DEFAULT
+	}
+
+	conv := cbconvert.New(options())
+	conv.Nfiles = len(files)
+	activeConv = conv
+	setBusy(true)
+
+	conv.OnStart = func() {
+		iup.PostMessage(iup.GetHandle("ProgressBar"), "convert", 0, conv)
+	}
+
+	conv.OnProgress = func() {
+		iup.PostMessage(iup.GetHandle("ProgressBar"), "progress", 0, conv)
+	}
+
+	iup.GetHandle("dlg").SetCallback("K_ANY", iup.KAnyFunc(func(ih iup.Ihandle, c int) int {
+		if c == iup.K_ESC {
+			conv.Cancel()
+		}
+
+		return iup.DEFAULT
+	})).SetCallback("CLOSE_CB", iup.CloseFunc(func(ih iup.Ihandle) int {
+		if err := os.RemoveAll(conv.Workdir); err != nil {
+			fmt.Println(err)
+		}
+
+		return iup.DEFAULT
+	}))
+
+	convertErr := func(err error) {
+		if errors.Is(err, context.Canceled) {
+			if err := os.RemoveAll(conv.Workdir); err != nil {
+				fmt.Println(err)
+			}
+
+			return
+		}
+
+		iup.PostMessage(iup.GetHandle("dlg"), err.Error(), 0, 0)
+		fmt.Println(err)
+
+		if err := os.RemoveAll(conv.Workdir); err != nil {
+			fmt.Println(err)
+		}
+	}
+
+	go func(c *cbconvert.Converter) {
+		if c.Opts.Combine {
+			if err := c.Combine(files); err != nil {
+				convertErr(err)
+			}
+		} else {
+			for _, file := range files {
+				if err := c.Convert(file); err != nil {
+					convertErr(err)
+					if errors.Is(err, context.Canceled) {
+						break
+					}
+
+					continue
+				}
+			}
+		}
+
+		iup.PostMessage(iup.GetHandle("ProgressBar"), "finish", 0, 0)
+	}(conv)
+
+	return iup.DEFAULT
+}
+
+func onOutputDirectory(ih iup.Ihandle) int {
+	args, err := fileDlg("Output Directory", false, true, outputDirKey)
+	if err != nil {
+		iup.PostMessage(iup.GetHandle("dlg"), err.Error(), 0, 0)
+		fmt.Println(err)
+
+		return iup.DEFAULT
+	}
+
+	if len(args) == 1 {
+		iup.GetHandle("OutDir").SetAttribute("VALUE", args[0])
+	}
+
+	setActive()
+
+	return iup.DEFAULT
+}
+
+func onOutputFile(ih iup.Ihandle) int {
+	name := saveDlg("Output File", outputDirKey)
+	if name != "" {
+		iup.GetHandle("OutFile").SetAttribute("VALUE", filepath.Base(name))
+		iup.GetHandle("OutDir").SetAttribute("VALUE", filepath.Dir(name))
+		setActive()
+	}
+
+	return iup.DEFAULT
+}
+
+func onFilterChanged(ih iup.Ihandle) int {
+	switch ih.GetInt("VALUE") {
+	case 1:
+		ih.SetAttribute("TIP", "NearestNeighbor is the fastest resampling filter, no antialiasing")
+	case 2:
+		ih.SetAttribute("TIP", "Box filter (averaging pixels)")
+	case 3:
+		ih.SetAttribute("TIP", "Linear is the bilinear filter, smooth and reasonably fast")
+	case 4:
+		ih.SetAttribute("TIP", "MitchellNetravali is a smooth bicubic filter")
+	case 5:
+		ih.SetAttribute("TIP", "CatmullRom is a sharp bicubic filter")
+	case 6:
+		ih.SetAttribute("TIP", "Gaussian is a blurring filter that uses gaussian function, useful for noise removal")
+	case 7:
+		ih.SetAttribute("TIP", "Lanczos is a high-quality resampling filter, it's slower than cubic filters")
+	}
+
+	previewPost()
+
+	return iup.DEFAULT
+}

cmd/cbconvert-gui/options.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"strconv"
+	"strings"
+
+	"github.com/gen2brain/cbconvert"
+	"github.com/gen2brain/iup-go/iup"
+)
+
+func options() cbconvert.Options {
+	var opts cbconvert.Options
+	opts.Recursive = iup.GetHandle("Recursive").GetAttribute("VALUE") == "ON"
+	opts.NoRGB = iup.GetHandle("NoRGB").GetAttribute("VALUE") == "ON"
+	opts.NoCover = iup.GetHandle("NoCover").GetAttribute("VALUE") == "ON"
+	opts.Size = iup.GetHandle("Size").GetInt("VALUE")
+	opts.OutDir = iup.GetHandle("OutDir").GetAttribute("VALUE")
+	opts.Suffix = iup.GetHandle("Suffix").GetAttribute("VALUE")
+	opts.NoConvert = iup.GetHandle("NoConvert").GetAttribute("VALUE") == "ON"
+	opts.NoNonImage = iup.GetHandle("NoNonImage").GetAttribute("VALUE") == "ON"
+	opts.Archive = strings.ToLower(iup.GetHandle("Archive").GetAttribute("VALUESTRING"))
+	opts.ZipLevel = zipLevel(iup.GetHandle("ZipLevel").GetAttribute("VALUESTRING"))
+	opts.Format = strings.ToLower(iup.GetHandle("Format").GetAttribute("VALUESTRING"))
+	opts.Width = iup.GetHandle("Width").GetInt("VALUE")
+	opts.Height = iup.GetHandle("Height").GetInt("VALUE")
+	opts.DPI = dpiValue(iup.GetHandle("DPI").GetAttribute("VALUE"))
+	opts.Fit = iup.GetHandle("Fit").GetAttribute("VALUE") == "ON"
+	opts.Filter = iup.GetHandle("Filter").GetInt("VALUE") - 1
+	opts.Quality = iup.GetHandle("Quality").GetInt("VALUE")
+	switch opts.Format {
+	case "webp", "avif", "jxl":
+		opts.Effort = iup.GetHandle("Effort").GetInt("VALUE")
+	default:
+		opts.Effort = -1
+	}
+	opts.Lossless = iup.GetHandle("Lossless").GetAttribute("VALUE") == "ON"
+	opts.Combine = iup.GetHandle("Combine").GetAttribute("VALUE") == "ON"
+	if opts.Combine {
+		opts.OutFile = iup.GetHandle("OutFile").GetAttribute("VALUE")
+	}
+	opts.Grayscale = iup.GetHandle("Grayscale").GetAttribute("VALUE") == "ON"
+	opts.Brightness = iup.GetHandle("Brightness").GetInt("VALUE")
+	opts.Contrast = iup.GetHandle("Contrast").GetInt("VALUE")
+	opts.Rotate = iup.GetHandle("Rotate").GetInt("VALUESTRING")
+
+	return opts
+}
+
+// shellArg quotes a command-line argument that contains whitespace.
+func shellArg(s string) string {
+	if strings.ContainsAny(s, " \t") {
+		return `"` + strings.ReplaceAll(s, `"`, `\"`) + `"`
+	}
+
+	return s
+}
+
+func commandLine() string {
+	parts := append([]string{"cbconvert", "convert"}, options().Args()...)
+	for _, file := range files {
+		parts = append(parts, file.Path)
+	}
+
+	for i, p := range parts {
+		parts[i] = shellArg(p)
+	}
+
+	return strings.Join(parts, " ")
+}
+
+func onCommand(iup.Ihandle) int {
+	iup.GetText("Command Line", commandLine(), -1)
+
+	return iup.DEFAULT
+}
+
+// zipLevel maps the compression dropdown selection to Options.ZipLevel.
+func zipLevel(value string) int {
+	switch value {
+	case "Default":
+		return -1
+	case "Store (none)":
+		return 0
+	default:
+		level, err := strconv.Atoi(value)
+		if err != nil {
+			return -1
+		}
+
+		return level
+	}
+}
+
+func dpiValue(value string) int {
+	dpi, err := strconv.Atoi(strings.TrimSpace(value))
+	if err != nil {
+		return 0
+	}
+
+	return dpi
+}

cmd/cbconvert-gui/settings.go

@@ -0,0 +1,248 @@
+package main
+
+import (
+	"fmt"
+	"slices"
+	"strconv"
+	"strings"
+
+	"github.com/gen2brain/iup-go/iup"
+)
+
+const (
+	pathsGroup    = "Paths"
+	profilesGroup = "Profiles"
+
+	inputDirKey  = "InputDir"
+	outputDirKey = "OutputDir"
+)
+
+type settingKind int
+
+const (
+	kindBool settingKind = iota
+	kindInt
+	kindStr
+)
+
+type setting struct {
+	handle string
+	kind   settingKind
+	def    string
+}
+
+var settings = []setting{
+	{"Recursive", kindBool, "OFF"},
+	{"NoRGB", kindBool, "OFF"},
+	{"NoCover", kindBool, "OFF"},
+	{"NoConvert", kindBool, "OFF"},
+	{"NoNonImage", kindBool, "OFF"},
+	{"Combine", kindBool, "OFF"},
+	{"Fit", kindBool, "OFF"},
+	{"Lossless", kindBool, "OFF"},
+	{"Grayscale", kindBool, "OFF"},
+	{"OutDir", kindStr, ""},
+	{"Suffix", kindStr, ""},
+	{"Width", kindStr, ""},
+	{"Height", kindStr, ""},
+	{"DPI", kindStr, "Default"},
+	{"Size", kindInt, "0"},
+	{"Quality", kindInt, "75"},
+	{"Effort", kindInt, "0"},
+	{"Brightness", kindInt, "0"},
+	{"Contrast", kindInt, "0"},
+	{"Format", kindInt, "1"},
+	{"Archive", kindInt, "1"},
+	{"ZipLevel", kindInt, "1"},
+	{"Filter", kindInt, "3"},
+	{"Rotate", kindInt, "1"},
+}
+
+func profileGroup(name string) string {
+	return "Profile:" + name
+}
+
+func profileNames() []string {
+	s := iup.ConfigGetVariableStr(config, profilesGroup, "Names")
+	if s == "" {
+		return nil
+	}
+
+	return strings.Split(s, ";")
+}
+
+func currentProfile() string {
+	return iup.ConfigGetVariableStrDef(config, profilesGroup, "Current", "Default")
+}
+
+func setStartDir(dlg iup.Ihandle, key string) {
+	if dir := iup.ConfigGetVariableStr(config, pathsGroup, key); dir != "" {
+		dlg.SetAttribute("DIRECTORY", dir)
+	}
+}
+
+func rememberDir(dlg iup.Ihandle, key string) {
+	dir := dlg.GetAttribute("DIRECTORY")
+	if dir == "" {
+		return
+	}
+
+	iup.ConfigSetVariableStr(config, pathsGroup, key, dir)
+	iup.ConfigSave(config)
+}
+
+func settingsSave(group string) {
+	for _, s := range settings {
+		h := iup.GetHandle(s.handle)
+		switch s.kind {
+		case kindBool:
+			v := 0
+			if h.GetAttribute("VALUE") == "ON" {
+				v = 1
+			}
+			iup.ConfigSetVariableInt(config, group, s.handle, v)
+		case kindInt:
+			iup.ConfigSetVariableInt(config, group, s.handle, h.GetInt("VALUE"))
+		case kindStr:
+			iup.ConfigSetVariableStr(config, group, s.handle, h.GetAttribute("VALUE"))
+		}
+	}
+
+	iup.ConfigSave(config)
+}
+
+// settingsApply sets every control from the given profile group, or from defaults when a group is empty.
+func settingsApply(group string) {
+	for _, s := range settings {
+		h := iup.GetHandle(s.handle)
+		switch s.kind {
+		case kindBool:
+			def := 0
+			if s.def == "ON" {
+				def = 1
+			}
+			v := def
+			if group != "" {
+				v = iup.ConfigGetVariableIntDef(config, group, s.handle, def)
+			}
+			if v != 0 {
+				h.SetAttribute("VALUE", "ON")
+			} else {
+				h.SetAttribute("VALUE", "OFF")
+			}
+		case kindInt:
+			def, _ := strconv.Atoi(s.def)
+			v := def
+			if group != "" {
+				v = iup.ConfigGetVariableIntDef(config, group, s.handle, def)
+			}
+			h.SetAttribute("VALUE", strconv.Itoa(v))
+		case kindStr:
+			v := s.def
+			if group != "" {
+				v = iup.ConfigGetVariableStrDef(config, group, s.handle, s.def)
+			}
+			h.SetAttribute("VALUE", v)
+		}
+	}
+
+	syncLabels()
+	setActive()
+	previewPost()
+}
+
+// syncLabels mirrors slider values into their value labels and retunes the effort slider for the current format.
+func syncLabels() {
+	iup.GetHandle("LabelQuality").SetAttribute("TITLE", iup.GetHandle("Quality").GetInt("VALUE"))
+	iup.GetHandle("LabelBrightness").SetAttribute("TITLE", iup.GetHandle("Brightness").GetInt("VALUE"))
+	iup.GetHandle("LabelContrast").SetAttribute("TITLE", iup.GetHandle("Contrast").GetInt("VALUE"))
+
+	format := strings.ToLower(iup.GetHandle("Format").GetAttribute("VALUESTRING"))
+	eff := iup.GetHandle("Effort").GetInt("VALUE")
+	setEffort(format)
+	switch format {
+	case "webp", "avif", "jxl":
+		val := iup.GetHandle("Effort")
+		val.SetAttribute("VALUE", strconv.Itoa(eff))
+		iup.GetHandle("LabelEffort").SetAttribute("TITLE", fmt.Sprintf("%s: %d", val.GetAttribute("EFFORTNAME"), eff))
+	}
+
+	iup.Refresh(iup.GetHandle("Tabs"))
+}
+
+func fillProfileList() {
+	list := iup.GetHandle("Profile")
+	list.SetAttribute("REMOVEITEM", "ALL")
+
+	cur := currentProfile()
+	sel := 1
+	for i, n := range profileNames() {
+		list.SetAttribute(strconv.Itoa(i+1), n)
+		if n == cur {
+			sel = i + 1
+		}
+	}
+
+	list.SetAttribute("VALUE", strconv.Itoa(sel))
+}
+
+// profilesInit loads the current profile on startup, creating a default one on the first run.
+func profilesInit() {
+	if len(profileNames()) == 0 {
+		iup.ConfigSetVariableStr(config, profilesGroup, "Names", "Default")
+		iup.ConfigSetVariableStr(config, profilesGroup, "Current", "Default")
+		settingsSave(profileGroup("Default"))
+	}
+
+	fillProfileList()
+	settingsApply(profileGroup(currentProfile()))
+}
+
+func onProfileSelect(ih iup.Ihandle) int {
+	name := ih.GetAttribute("VALUESTRING")
+	if name == "" {
+		return iup.DEFAULT
+	}
+
+	iup.ConfigSetVariableStr(config, profilesGroup, "Current", name)
+	iup.ConfigSave(config)
+
+	settingsApply(profileGroup(name))
+
+	return iup.DEFAULT
+}
+
+func onSave(iup.Ihandle) int {
+	name := currentProfile()
+	if iup.GetParam("Save Profile", nil, "Name: %s\n", &name) != 1 {
+		return iup.DEFAULT
+	}
+
+	name = strings.TrimSpace(name)
+	if name == "" || strings.ContainsAny(name, ".;") {
+		iup.Message("Invalid Name", "Profile name must not be empty or contain '.' or ';'.")
+
+		return iup.DEFAULT
+	}
+
+	settingsSave(profileGroup(name))
+
+	names := profileNames()
+	if !slices.Contains(names, name) {
+		names = append(names, name)
+		iup.ConfigSetVariableStr(config, profilesGroup, "Names", strings.Join(names, ";"))
+	}
+
+	iup.ConfigSetVariableStr(config, profilesGroup, "Current", name)
+	iup.ConfigSave(config)
+
+	fillProfileList()
+
+	return iup.DEFAULT
+}
+
+func onReset(iup.Ihandle) int {
+	settingsApply("")
+
+	return iup.DEFAULT
+}

cmd/cbconvert-gui/state.go

@@ -0,0 +1,124 @@
+package main
+
+import "github.com/gen2brain/iup-go/iup"
+
+func setActive() {
+	if busy {
+		return
+	}
+
+	opts := options()
+	count := iup.GetHandle("Table").GetInt("NUMLIN")
+
+	if count == 0 {
+		iup.GetHandle("Remove").SetAttribute("ACTIVE", "NO")
+		iup.GetHandle("RemoveAll").SetAttribute("ACTIVE", "NO")
+
+		iup.GetHandle("Preview").SetAttribute("IMAGE", "logo")
+		iup.GetHandle("PreviewInfo").SetAttribute("TITLE", "")
+	} else {
+		if index != -1 {
+			iup.GetHandle("Remove").SetAttribute("ACTIVE", "YES")
+		}
+		iup.GetHandle("RemoveAll").SetAttribute("ACTIVE", "YES")
+	}
+
+	active := "YES"
+	var tip string
+	switch {
+	case count == 0 && opts.OutDir == "":
+		active, tip = "NO", "Add files and set output directory"
+	case count == 0:
+		active, tip = "NO", "Add files"
+	case opts.OutDir == "":
+		active, tip = "NO", "Set output directory"
+	}
+
+	enabledTip := map[string]string{
+		"Thumbnail": "Extract cover thumbnails",
+		"Cover":     "Extract covers",
+		"Convert":   "Convert files to the selected format",
+	}
+
+	for _, h := range []string{"Thumbnail", "Cover", "Convert"} {
+		b := iup.GetHandle(h)
+		b.SetAttribute("ACTIVE", active)
+		if active == "YES" {
+			b.SetAttribute("TIP", enabledTip[h])
+		} else {
+			b.SetAttribute("TIP", tip)
+		}
+	}
+
+	if opts.NoConvert {
+		iup.GetHandle("VboxImage").SetAttribute("ACTIVE", "NO")
+		iup.GetHandle("VboxTransform").SetAttribute("ACTIVE", "NO")
+	} else {
+		iup.GetHandle("VboxImage").SetAttribute("ACTIVE", "YES")
+		iup.GetHandle("VboxTransform").SetAttribute("ACTIVE", "YES")
+	}
+
+	canLossless := opts.Format == "webp" || opts.Format == "avif" || opts.Format == "jxl"
+	losslessOn := canLossless && opts.Lossless
+
+	if (opts.Format == "jpeg" || canLossless) && !opts.NoConvert && !losslessOn {
+		iup.GetHandle("VboxQuality").SetAttribute("ACTIVE", "YES")
+	} else {
+		iup.GetHandle("VboxQuality").SetAttribute("ACTIVE", "NO")
+	}
+
+	if canLossless && !opts.NoConvert {
+		iup.GetHandle("VboxEffort").SetAttribute("ACTIVE", "YES")
+		iup.GetHandle("Lossless").SetAttribute("ACTIVE", "YES")
+	} else {
+		iup.GetHandle("VboxEffort").SetAttribute("ACTIVE", "NO")
+		iup.GetHandle("Lossless").SetAttribute("ACTIVE", "NO")
+	}
+
+	if opts.Width != 0 && opts.Height != 0 && !opts.NoConvert {
+		iup.GetHandle("Fit").SetAttribute("ACTIVE", "YES")
+	} else {
+		iup.GetHandle("Fit").SetAttribute("ACTIVE", "NO")
+	}
+
+	if opts.Combine {
+		iup.GetHandle("VboxOutFile").SetAttribute("ACTIVE", "YES")
+	} else {
+		iup.GetHandle("VboxOutFile").SetAttribute("ACTIVE", "NO")
+	}
+
+	if opts.Archive == "zip" {
+		iup.GetHandle("VboxZipLevel").SetAttribute("ACTIVE", "YES")
+	} else {
+		iup.GetHandle("VboxZipLevel").SetAttribute("ACTIVE", "NO")
+	}
+}
+
+// setBusy locks the UI while an operation runs and turns Convert into a Cancel button.
+func setBusy(on bool) {
+	busy = on
+
+	// Controls not governed by setActive; setActive owns the rest.
+	always := "YES"
+	if on {
+		always = "NO"
+	}
+	for _, h := range []string{"AddFiles", "AddDir", "Profile", "Reset", "Save", "Command", "Tabs", "Table"} {
+		iup.GetHandle(h).SetAttribute("ACTIVE", always)
+	}
+
+	convert := iup.GetHandle("Convert")
+	if on {
+		for _, h := range []string{"Remove", "RemoveAll", "Thumbnail", "Cover"} {
+			iup.GetHandle(h).SetAttribute("ACTIVE", "NO")
+		}
+		convert.SetAttribute("ACTIVE", "YES")
+		convert.SetAttribute("TITLE", "Cancel")
+		convert.SetAttribute("TIP", "Cancel the running operation (or press Esc)")
+	} else {
+		activeConv = nil
+		convert.SetAttribute("TITLE", "&Convert")
+		convert.SetAttribute("TIP", "Convert files to the selected format")
+		setActive() // restores the conditional buttons and option boxes
+	}
+}

cmd/cbconvert-gui/widgets.go

@@ -0,0 +1,653 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"image/gif"
+	"net/url"
+	"strconv"
+	"strings"
+
+	"github.com/gen2brain/cbconvert"
+	"github.com/gen2brain/iup-go/iup"
+)
+
+func setEffort(format string) {
+	val := iup.GetHandle("Effort")
+
+	var name string
+
+	switch format {
+	case "webp":
+		val.SetAttributes("MIN=0, MAX=6, SHOWTICKS=7, VALUE=4")
+		val.SetAttribute("TIP", "WEBP method, higher is better/slower (0-6, default 4)")
+		name = "Method"
+	case "avif":
+		val.SetAttributes("MIN=0, MAX=10, SHOWTICKS=11, VALUE=10")
+		val.SetAttribute("TIP", "AVIF speed, higher is faster/worse (0-10, default 10)")
+		name = "Speed"
+	case "jxl":
+		val.SetAttributes("MIN=1, MAX=10, SHOWTICKS=10, VALUE=7")
+		val.SetAttribute("TIP", "JXL effort, higher is better/slower (1-10, default 7)")
+		name = "Effort"
+	default:
+		return
+	}
+
+	val.SetAttribute("EFFORTNAME", name)
+	iup.GetHandle("LabelEffort").SetAttribute("TITLE", fmt.Sprintf("%s: %d", name, val.GetInt("VALUE")))
+	iup.Refresh(iup.GetHandle("LabelEffort"))
+}
+
+// tableRowColors sets the alternating row colors for dark or light mode.
+func tableRowColors(t iup.Ihandle, dark bool) {
+	even, odd := "#F0F0F0", "#FFFFFF"
+	if dark {
+		even, odd = "#3A3A3A", "#2D2D2D"
+	}
+	t.SetAttribute("EVENROWCOLOR", even)
+	t.SetAttribute("ODDROWCOLOR", odd)
+}
+
+func list() iup.Ihandle {
+	t := iup.Table().SetHandle("Table")
+	t.SetAttributes(map[string]string{
+		"EXPAND":         "YES",
+		"NUMCOL":         "3",
+		"NUMLIN":         "0",
+		"TITLE1":         "Title",
+		"TITLE2":         "Type",
+		"TITLE3":         "Size (MiB)",
+		"WIDTH1":         "150",
+		"WIDTH2":         "50",
+		"WIDTH3":         "100",
+		"ALIGNMENT2":     "ACENTER",
+		"ALIGNMENT3":     "ARIGHT",
+		"SELECTIONMODE":  "SINGLE",
+		"USERRESIZE":     "YES",
+		"STRETCHLAST":    "NO",
+		"FOCUSRECT":      "NO",
+		"SORTABLE":       "YES",
+		"ALTERNATECOLOR": "YES",
+	})
+
+	tableRowColors(t, iup.GetGlobal("DARKMODE") == "YES" && iup.GetGlobal("AUTODARKMODE") == "YES")
+
+	t.SetCallback("ENTERITEM_CB", iup.EnterItemFunc(func(ih iup.Ihandle, lin, col int) int {
+		index = lin - 1
+		setActive()
+		previewPost()
+
+		return iup.DEFAULT
+	}))
+
+	t.SetCallback("SORT_CB", iup.TableSortFunc(onSort))
+
+	t.SetCallback("DROPFILES_CB", iup.DropFilesFunc(func(ih iup.Ihandle, fileName string, num, x, y int) int {
+		dec, err := url.QueryUnescape(fileName)
+		if err != nil {
+			iup.PostMessage(iup.GetHandle("dlg"), err.Error(), 0, 0)
+			fmt.Println(err)
+
+			return iup.DEFAULT
+		}
+
+		conv := cbconvert.New(options())
+
+		fs, err := conv.Files([]string{dec})
+		if err != nil {
+			iup.PostMessage(iup.GetHandle("dlg"), err.Error(), 0, 0)
+			fmt.Println(err)
+
+			return iup.DEFAULT
+		}
+
+		wasEmpty := len(files) == 0
+
+		for _, file := range fs {
+			appendFile(file)
+		}
+
+		if wasEmpty && len(files) > 0 {
+			selectRow(0)
+		}
+
+		setActive()
+
+		if wasEmpty {
+			previewPost()
+		}
+
+		return iup.DEFAULT
+	}))
+
+	return iup.Vbox(t)
+}
+
+func previewSize() (int, int) {
+	var width, height int
+	sp := strings.Split(iup.GetHandle("Preview").GetAttribute("RASTERSIZE"), "x")
+	if len(sp) == 2 {
+		width, _ = strconv.Atoi(sp[0])
+		height, _ = strconv.Atoi(sp[1])
+	}
+
+	return width, height
+}
+
+func preview() iup.Ihandle {
+	return iup.Frame(
+		iup.Vbox(
+			iup.Label("").SetAttributes("EXPAND=YES, ALIGNMENT=ACENTER, MINSIZE=400x, IMAGE=cover").SetHandle("Preview").
+				SetCallback("POSTMESSAGE_CB", iup.PostMessageFunc(func(ih iup.Ihandle, s string, i int, p any) int {
+					img := p.(cbconvert.Image)
+
+					iup.GetHandle("Loading").SetAttributes("VISIBLE=NO, STOP=YES")
+
+					if img.Image != nil && len(s) == 0 {
+						iup.Destroy(iup.GetHandle("cover"))
+						iup.ImageFromImage(img.Image).SetHandle("cover")
+
+						ih.SetAttribute("IMAGE", "cover")
+						iup.GetHandle("PreviewInfo").SetAttribute("TITLE", fmt.Sprintf("%s (%dx%d)", img.SizeHuman, img.Width, img.Height))
+					} else {
+						ih.SetAttribute("IMAGE", "logo")
+						iup.GetHandle("PreviewInfo").SetAttribute("TITLE", "")
+
+						sp := strings.Split(s, ": ")
+						if len(sp) > 1 {
+							iup.MessageError(ih, fmt.Sprintf("%s\n\n%s", sp[0], strings.Join(sp[1:], ": ")))
+						}
+					}
+
+					return iup.DEFAULT
+				})),
+			iup.Label("").SetAttributes("EXPAND=HORIZONTAL, ALIGNMENT=ACENTER").SetHandle("PreviewInfo"),
+		),
+	)
+}
+
+func tabInput() iup.Ihandle {
+	return iup.Hbox(
+		iup.Vbox(
+			iup.Toggle(" Recurse SubDirectories").SetHandle("Recursive").
+				SetAttributes(`TIP="Process subdirectories recursively"`),
+			iup.Toggle(" Only Grayscale Images").SetHandle("NoRGB").
+				SetAttributes(`TIP="Do not convert images that have RGB colorspace"`),
+			iup.Toggle(" Exclude Cover").SetHandle("NoCover").
+				SetAttributes(`TIP="Do not convert the cover image"`),
+			iup.Toggle(" Remove Non-Image Files from the Archive").SetHandle("NoNonImage").
+				SetAttribute("TIP", "Remove .nfo, .xml, .txt files from the archive"),
+			iup.Toggle(" Do not Transform or Convert Images").SetHandle("NoConvert").
+				SetAttributes(`TIP="Copy images from archive or directory without modifications"`).
+				SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+					setActive()
+
+					return iup.DEFAULT
+				})),
+		).SetAttributes("NGAP=10"),
+		iup.Space().SetAttribute("SIZE", "15"),
+		iup.Vbox(
+			iup.Vbox(
+				iup.Label("Minimum Size (MiB):"),
+				iup.Text().SetAttributes(`SPIN=YES, SPINMAX=2048, VISIBLECOLUMNS=4, MASK="/d*"`).SetHandle("Size").
+					SetAttributes(`TIP="Process only files larger than minimum size"`),
+			),
+			iup.Vbox(
+				iup.Label("Document DPI:"),
+				iup.List().SetAttributes(map[string]string{
+					"DROPDOWN":       "YES",
+					"EDITBOX":        "YES",
+					"VISIBLECOLUMNS": "6",
+					"VALUE":          "Default",
+					"1":              "Default",
+					"2":              "150",
+					"3":              "300",
+					"4":              "600",
+					"5":              "1200",
+				}).SetHandle("DPI").
+					SetAttribute("TIP", "Resolution for rendering documents (PDF, EPUB, etc.); Default is 300"),
+			),
+		).SetAttributes("NGAP=10"),
+	).SetHandle("VboxInput")
+}
+
+func tabOutput() iup.Ihandle {
+	return iup.Hbox(
+		iup.Vbox(
+			iup.Vbox(
+				iup.Label("Output Directory:"),
+				iup.Text().SetAttributes("VISIBLECOLUMNS=16, MINSIZE=100x").SetHandle("OutDir").
+					SetAttribute("TIP", "Directory where converted files are written (required)").
+					SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+						setActive()
+
+						return iup.DEFAULT
+					})),
+				iup.Space().SetAttribute("SIZE", "5x0"),
+				iup.Button("Browse...").SetAttributes("PADDING=DEFAULTBUTTONPADDING").
+					SetCallback("ACTION", iup.ActionFunc(onOutputDirectory)),
+			),
+			iup.Vbox(
+				iup.Label("Add Suffix to Output File:"),
+				iup.Text().SetAttributes("VISIBLECOLUMNS=16, MINSIZE=100x").SetHandle("Suffix").
+					SetAttribute("TIP", "Add suffix to filename, i.e. filename_suffix.cbz"),
+			),
+			iup.Vbox(
+				iup.Label("Archive Format:"),
+				iup.List().SetAttributes(map[string]string{
+					"DROPDOWN": "YES",
+					"VALUE":    "1",
+					"1":        "ZIP",
+					"2":        "TAR",
+				}).SetHandle("Archive").
+					SetAttribute("TIP", "Output container: ZIP (.cbz) or uncompressed TAR (.cbt)").
+					SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+						setActive()
+
+						return iup.DEFAULT
+					})),
+			),
+			iup.Vbox(
+				iup.Label("Compression:"),
+				iup.List().SetAttributes(map[string]string{
+					"DROPDOWN": "YES",
+					"VALUE":    "1",
+					"1":        "Default",
+					"2":        "Store (none)",
+					"3":        "1",
+					"4":        "2",
+					"5":        "3",
+					"6":        "4",
+					"7":        "5",
+					"8":        "6",
+					"9":        "7",
+					"10":       "8",
+					"11":       "9",
+				}).SetHandle("ZipLevel").
+					SetAttribute("TIP", "ZIP compression: Store disables it, 1 is fastest, 9 is smallest"),
+			).SetHandle("VboxZipLevel"),
+		).SetAttributes("NGAP=10"),
+		iup.Space().SetAttribute("SIZE", "15"),
+		iup.Vbox(
+			iup.Vbox(
+				iup.Toggle(" Combine into single file").SetHandle("Combine").
+					SetAttributes(`TIP="Merge all listed files into one archive"`).
+					SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+						setActive()
+
+						return iup.DEFAULT
+					})),
+			),
+			iup.Vbox(
+				iup.Label("Output File:"),
+				iup.Text().SetAttributes("VISIBLECOLUMNS=16, MINSIZE=100x").SetHandle("OutFile").
+					SetAttribute("TIP", "Combined file name (default: first input + -combined)"),
+				iup.Space().SetAttribute("SIZE", "5x0"),
+				iup.Button("Browse...").SetAttributes("PADDING=DEFAULTBUTTONPADDING").
+					SetCallback("ACTION", iup.ActionFunc(onOutputFile)),
+			).SetHandle("VboxOutFile"),
+		).SetAttributes("NGAP=10"),
+	).SetHandle("VboxOutput")
+}
+
+func tabImage() iup.Ihandle {
+	return iup.Hbox(
+		iup.Vbox(
+			iup.Vbox(
+				iup.Label("Format:"),
+				iup.List().SetAttributes(map[string]string{
+					"DROPDOWN": "YES",
+					"VALUE":    "1",
+					"1":        "JPEG",
+					"2":        "PNG",
+					"3":        "TIFF",
+					"4":        "BMP",
+					"5":        "WEBP",
+					"6":        "AVIF",
+					"7":        "JXL",
+				}).SetHandle("Format").
+					SetAttribute("TIP", "Output image format for the converted pages").
+					SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+						setEffort(strings.ToLower(ih.GetAttribute("VALUESTRING")))
+						setActive()
+						previewPost()
+
+						return iup.DEFAULT
+					})),
+			),
+			iup.Vbox(
+				iup.Label("Size:"),
+				iup.Hbox(
+					iup.Text().SetAttributes(`CUEBANNER="width", VISIBLECOLUMNS=6, MASK="/d*"`).SetHandle("Width").
+						SetAttribute("TIP", "If one of, width or height is not set, the image aspect ratio is preserved").
+						SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+							setActive()
+							ih.SetAttribute("MYVALUE", ih.GetInt("VALUE"))
+
+							return iup.DEFAULT
+						})).
+						SetCallback("KILLFOCUS_CB", iup.KillFocusFunc(func(ih iup.Ihandle) int {
+							if ih.GetAttribute("MYVALUE") != "" {
+								previewPost()
+							}
+							ih.SetAttribute("MYVALUE", "")
+
+							return iup.DEFAULT
+						})),
+					iup.Space().SetAttribute("SIZE", "2"),
+					iup.Label("x"),
+					iup.Space().SetAttribute("SIZE", "2"),
+					iup.Text().SetAttributes(`CUEBANNER="height", VISIBLECOLUMNS=6, MASK="/d*"`).SetHandle("Height").
+						SetAttribute("TIP", "If one of, width or height is not set, the image aspect ratio is preserved").
+						SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+							setActive()
+							ih.SetAttribute("MYVALUE", ih.GetInt("VALUE"))
+
+							return iup.DEFAULT
+						})).
+						SetCallback("KILLFOCUS_CB", iup.KillFocusFunc(func(ih iup.Ihandle) int {
+							if ih.GetAttribute("MYVALUE") != "" {
+								previewPost()
+							}
+							ih.SetAttribute("MYVALUE", "")
+
+							return iup.DEFAULT
+						})),
+				).SetAttributes("ALIGNMENT=ACENTER, NMARGIN=0"),
+			),
+			iup.Vbox(
+				iup.Toggle(" Best Fit").SetHandle("Fit").
+					SetAttributes(`TIP="Best fit for required width and height"`),
+			),
+			iup.Vbox(
+				iup.Label("Resize Filter:"),
+				iup.List().SetAttributes(map[string]string{
+					"DROPDOWN": "YES",
+					"VALUE":    "3",
+					"TIP":      "Linear is the bilinear filter, smooth and reasonably fast",
+					"1":        "NearestNeighbor",
+					"2":        "Box",
+					"3":        "Linear",
+					"4":        "MitchellNetravali",
+					"5":        "CatmullRom",
+					"6":        "Gaussian",
+					"7":        "Lanczos",
+				}).SetHandle("Filter").SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(onFilterChanged)),
+			),
+		).SetAttributes("NGAP=10"),
+		iup.Space().SetAttribute("SIZE", "15"),
+		iup.Vbox(
+			iup.Vbox(
+				iup.Hbox(
+					iup.Label("Quality: "),
+					iup.Label("75").SetHandle("LabelQuality"),
+				).SetAttributes("NMARGIN=0"),
+				iup.Val("").SetAttributes(`MIN=0, MAX=100, VALUE=75, SHOWTICKS=10`).SetHandle("Quality").
+					SetAttribute("TIP", "Quality affects JPEG, WEBP, AVIF and JXL").
+					SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+						iup.GetHandle("LabelQuality").SetAttribute("TITLE", ih.GetInt("VALUE"))
+						iup.Refresh(iup.GetHandle("LabelQuality"))
+						ih.SetAttribute("MYVALUE", ih.GetInt("VALUE"))
+
+						return iup.DEFAULT
+					})).
+					SetCallback("KILLFOCUS_CB", iup.KillFocusFunc(func(ih iup.Ihandle) int {
+						if ih.GetAttribute("MYVALUE") != "" {
+							previewPost()
+						}
+						ih.SetAttribute("MYVALUE", "")
+
+						return iup.DEFAULT
+					})),
+			).SetHandle("VboxQuality"),
+			iup.Vbox(
+				iup.Label("Effort:").SetHandle("LabelEffort"),
+				iup.Val("").SetAttributes(`MIN=0, MAX=10, VALUE=0, SHOWTICKS=11`).SetHandle("Effort").
+					SetAttribute("TIP", "Encoder speed/effort (WEBP, AVIF, JXL)").
+					SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+						iup.GetHandle("LabelEffort").SetAttribute("TITLE", fmt.Sprintf("%s: %d", ih.GetAttribute("EFFORTNAME"), ih.GetInt("VALUE")))
+						iup.Refresh(iup.GetHandle("LabelEffort"))
+						ih.SetAttribute("MYVALUE", ih.GetInt("VALUE"))
+
+						return iup.DEFAULT
+					})).
+					SetCallback("KILLFOCUS_CB", iup.KillFocusFunc(func(ih iup.Ihandle) int {
+						if ih.GetAttribute("MYVALUE") != "" {
+							previewPost()
+						}
+						ih.SetAttribute("MYVALUE", "")
+
+						return iup.DEFAULT
+					})),
+			).SetHandle("VboxEffort"),
+			iup.Vbox(
+				iup.Toggle(" Lossless").SetHandle("Lossless").
+					SetAttributes(`TIP="Lossless compression (WEBP, AVIF, JXL), ignores quality"`).
+					SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+						setActive()
+						previewPost()
+
+						return iup.DEFAULT
+					})),
+			),
+			iup.Vbox(
+				iup.Toggle(" Grayscale").SetHandle("Grayscale").
+					SetAttributes(`TIP="Convert images to grayscale (monochromatic)"`).
+					SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+						previewPost()
+
+						return iup.DEFAULT
+					})),
+			),
+		).SetAttributes("NGAP=10"),
+	).SetHandle("VboxImage")
+}
+
+func tabTransform() iup.Ihandle {
+	return iup.Vbox(
+		iup.Vbox(
+			iup.Hbox(
+				iup.Label("Brightness: "),
+				iup.Label("0").SetHandle("LabelBrightness"),
+			).SetAttributes("ALIGNMENT=ACENTER, NMARGIN=0"),
+			iup.Val("").SetAttributes(`MIN=-100, MAX=100, VALUE=0, SHOWTICKS=10`).SetHandle("Brightness").
+				SetAttributes(`TIP="Adjust the brightness of the images"`).
+				SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+					iup.GetHandle("LabelBrightness").SetAttribute("TITLE", iup.GetHandle("Brightness").GetInt("VALUE"))
+					iup.Refresh(iup.GetHandle("LabelBrightness"))
+					ih.SetAttribute("MYVALUE", ih.GetInt("VALUE"))
+
+					return iup.DEFAULT
+				})).
+				SetCallback("KILLFOCUS_CB", iup.KillFocusFunc(func(ih iup.Ihandle) int {
+					if ih.GetAttribute("MYVALUE") != "" {
+						previewPost()
+					}
+					ih.SetAttribute("MYVALUE", "")
+
+					return iup.DEFAULT
+				})),
+		),
+		iup.Vbox(
+			iup.Hbox(
+				iup.Label("Contrast: "),
+				iup.Label("0").SetHandle("LabelContrast"),
+			).SetAttributes("ALIGNMENT=ACENTER, NMARGIN=0"),
+			iup.Val("").SetAttributes(`MIN=-100, MAX=100, VALUE=0, SHOWTICKS=10`).SetHandle("Contrast").
+				SetAttributes(`TIP="Adjust the contrast of the images"`).
+				SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+					iup.GetHandle("LabelContrast").SetAttribute("TITLE", iup.GetHandle("Contrast").GetInt("VALUE"))
+					iup.Refresh(iup.GetHandle("LabelContrast"))
+					ih.SetAttribute("MYVALUE", ih.GetInt("VALUE"))
+
+					return iup.DEFAULT
+				})).
+				SetCallback("KILLFOCUS_CB", iup.KillFocusFunc(func(ih iup.Ihandle) int {
+					if ih.GetAttribute("MYVALUE") != "" {
+						previewPost()
+					}
+					ih.SetAttribute("MYVALUE", "")
+
+					return iup.DEFAULT
+				})),
+		),
+		iup.Vbox(
+			iup.Label("Rotate:"),
+			iup.List().SetAttributes(map[string]string{
+				"DROPDOWN": "YES",
+				"VALUE":    "1",
+				"1":        "0",
+				"2":        "90",
+				"3":        "180",
+				"4":        "270",
+			}).SetHandle("Rotate").
+				SetAttribute("TIP", "Rotate every page clockwise by the given angle in degrees").
+				SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+					previewPost()
+
+					return iup.DEFAULT
+				})),
+		),
+	).SetHandle("VboxTransform").SetAttributes("NGAP=10")
+}
+
+func tabs() iup.Ihandle {
+	return iup.Tabs(
+		tabInput().SetAttributes("TABTITLE=Input, NMARGIN=10x10"),
+		tabOutput().SetAttributes("TABTITLE=Output, NMARGIN=10x10"),
+		tabImage().SetAttributes("TABTITLE=Image, NMARGIN=10x10"),
+		tabTransform().SetAttributes("TABTITLE=Transform, NMARGIN=10x10"),
+	).SetHandle("Tabs")
+}
+
+func buttons() iup.Ihandle {
+	addFiles := iup.Button("Add &Files...").SetHandle("AddFiles").SetAttributes("PADDING=DEFAULTBUTTONPADDING").
+		SetCallback("ACTION", iup.ActionFunc(onAddFiles))
+	addDir := iup.Button("Add &Dir...").SetHandle("AddDir").SetAttributes("PADDING=DEFAULTBUTTONPADDING").
+		SetCallback("ACTION", iup.ActionFunc(onAddDir))
+	remove := iup.Button("Remove").SetHandle("Remove").SetAttributes("PADDING=DEFAULTBUTTONPADDING").
+		SetCallback("ACTION", iup.ActionFunc(onRemove))
+	removeAll := iup.Button("Remove All").SetHandle("RemoveAll").SetAttributes("PADDING=DEFAULTBUTTONPADDING").
+		SetCallback("ACTION", iup.ActionFunc(onRemoveAll))
+	thumbnail := iup.Button("Thumbnail").SetHandle("Thumbnail").SetAttributes("PADDING=DEFAULTBUTTONPADDING").
+		SetCallback("ACTION", iup.ActionFunc(onThumbnail))
+	cover := iup.Button("Cover").SetHandle("Cover").SetAttributes("PADDING=DEFAULTBUTTONPADDING").
+		SetCallback("ACTION", iup.ActionFunc(onCover))
+	convert := iup.Button("&Convert").SetHandle("Convert").SetAttributes("PADDING=DEFAULTBUTTONPADDING").
+		SetCallback("ACTION", iup.ActionFunc(onConvert))
+	reset := iup.Button("Reset").SetHandle("Reset").SetAttributes("PADDING=DEFAULTBUTTONPADDING").
+		SetAttribute("TIP", "Restore all settings to their defaults").
+		SetCallback("ACTION", iup.ActionFunc(onReset))
+	save := iup.Button("Save").SetHandle("Save").SetAttributes("PADDING=DEFAULTBUTTONPADDING").
+		SetAttribute("TIP", "Save current settings to a profile").
+		SetCallback("ACTION", iup.ActionFunc(onSave))
+
+	command := iup.Button("Command").SetHandle("Command").SetAttributes("PADDING=DEFAULTBUTTONPADDING").
+		SetAttribute("TIP", "Show the equivalent command line").
+		SetCallback("ACTION", iup.ActionFunc(onCommand))
+
+	profile := iup.List().SetAttributes("DROPDOWN=YES").SetHandle("Profile").
+		SetAttribute("TIP", "Select a settings profile").
+		SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(onProfileSelect))
+
+	iup.Normalizer(addFiles, addDir, remove, removeAll, thumbnail, cover, convert, reset, save, command).SetAttribute("NORMALIZE", "BOTH")
+	iup.Normalizer(addFiles, addDir, remove, removeAll, thumbnail, cover, convert, reset, save, command, profile).SetAttribute("NORMALIZE", "HORIZONTAL")
+
+	return iup.Vbox(
+		iup.Vbox(
+			addFiles,
+			addDir,
+			remove,
+			removeAll,
+		).SetAttribute("NGAP", "2"),
+		iup.Space().SetAttribute("SIZE", "x5"),
+		iup.Vbox(
+			thumbnail,
+			cover,
+		).SetAttribute("NGAP", "2"),
+		iup.Space().SetAttribute("SIZE", "x5"),
+		iup.Vbox(
+			convert,
+		),
+		iup.Fill(),
+		iup.Vbox(
+			iup.Label("Profile:"),
+			profile,
+			reset,
+			save,
+			command,
+		).SetAttribute("NGAP", "2"),
+	).SetHandle("Buttons").SetAttributes("ALIGNMENT=ACENTER")
+}
+
+func status() iup.Ihandle {
+	return iup.Hbox(
+		loading(),
+		iup.Fill(),
+		iup.Label("File 1 of 1").SetHandle("LabelStatus1").SetAttributes("VISIBLE=NO"),
+		iup.Space().SetAttribute("SIZE", "5"),
+		iup.Label("(000/000)").SetHandle("LabelStatus2").SetAttributes("VISIBLE=NO"),
+		iup.Space().SetAttribute("SIZE", "5"),
+		iup.ProgressBar().SetAttributes("VISIBLE=NO").SetHandle("ProgressBar").
+			SetCallback("POSTMESSAGE_CB", iup.PostMessageFunc(func(ih iup.Ihandle, s string, i int, p any) int {
+				switch s {
+				case "convert":
+					conv := p.(*cbconvert.Converter)
+					ih.SetAttributes("VALUE=0, VISIBLE=YES")
+					ih.SetAttribute("MAX", conv.Ncontents)
+
+					iup.GetHandle("LabelStatus1").SetAttribute("TITLE", fmt.Sprintf("File %d of %d", conv.CurrFile, conv.Nfiles))
+					iup.GetHandle("LabelStatus1").SetAttributes("VISIBLE=YES")
+					iup.GetHandle("LabelStatus2").SetAttributes("VISIBLE=YES")
+
+					iup.Refresh(iup.GetHandle("StatusBar"))
+				case "start":
+					conv := p.(*cbconvert.Converter)
+					ih.SetAttributes("VALUE=0, VISIBLE=YES")
+					ih.SetAttribute("MAX", conv.Nfiles)
+
+					iup.GetHandle("LabelStatus2").SetAttributes("VISIBLE=YES")
+				case "progress":
+					conv := p.(*cbconvert.Converter)
+					ih.SetAttribute("VALUE", conv.CurrContent)
+					iup.GetHandle("LabelStatus2").SetAttribute("TITLE", fmt.Sprintf("(%03d/%03d)", conv.CurrContent, conv.Ncontents))
+
+					iup.Refresh(iup.GetHandle("StatusBar"))
+				case "progress2":
+					conv := p.(*cbconvert.Converter)
+					ih.SetAttribute("VALUE", conv.CurrFile)
+					iup.GetHandle("LabelStatus2").SetAttribute("TITLE", fmt.Sprintf("(%03d/%03d)", conv.CurrFile, conv.Nfiles))
+
+					iup.Refresh(iup.GetHandle("StatusBar"))
+				case "finish":
+					setBusy(false)
+
+					iup.GetHandle("LabelStatus1").SetAttributes(`TITLE="", VISIBLE=NO`)
+					iup.GetHandle("LabelStatus2").SetAttributes(`TITLE="", VISIBLE=NO`)
+					ih.SetAttributes("VALUE=0, VISIBLE=NO")
+
+					iup.Refresh(iup.GetHandle("StatusBar"))
+
+					iup.GetHandle("dlg").SetCallback("K_ANY", nil)
+					iup.GetHandle("dlg").SetCallback("CLOSE_CB", nil)
+				}
+
+				return iup.DEFAULT
+			})),
+		iup.Space().SetAttribute("SIZE", "5x0"),
+	).SetAttributes("ALIGNMENT=ACENTER, NMARGIN=5x5").SetHandle("StatusBar")
+}
+
+func loading() iup.Ihandle {
+	img, _ := gif.DecodeAll(bytes.NewReader(appLoading))
+	animation := iup.User()
+
+	for idx, i := range img.Image {
+		name := fmt.Sprintf("Loading%d", idx)
+		iup.ImageFromImage(i).SetHandle(name)
+		iup.Append(animation, iup.GetHandle(name))
+	}
+
+	return iup.AnimatedLabel(animation).SetAttributes("VISIBLE=NO").SetHandle("Loading")
+}

cmd/cbconvert/main.go

@@ -175,6 +175,7 @@ func parseFlags() (cbconvert.Options, []string) {
 	convert.IntVar(&opts.Width, "width", 0, "Image width")
 	convert.IntVar(&opts.Height, "height", 0, "Image height")
 	convert.BoolVar(&opts.Fit, "fit", false, "Best fit for required width and height")
+	convert.IntVar(&opts.DPI, "dpi", 0, "Document rendering resolution in DPI (PDF, EPUB, etc.), 0 uses the default (300)")
 	convert.StringVar(&opts.Format, "format", "jpeg", "Image format, valid values are jpeg, png, tiff, bmp, webp, avif, jxl")
 	convert.StringVar(&opts.Archive, "archive", "zip", "Archive format, valid values are zip, tar")
 	convert.IntVar(&opts.ZipLevel, "zip-level", -1, "ZIP compression level, 0 disables compression, 1-9 sets deflate level (1 fastest, 9 smallest), -1 uses the default")
@@ -202,6 +203,7 @@ func parseFlags() (cbconvert.Options, []string) {
 	cover.IntVar(&opts.Width, "width", 0, "Image width")
 	cover.IntVar(&opts.Height, "height", 0, "Image height")
 	cover.BoolVar(&opts.Fit, "fit", false, "Best fit for required width and height")
+	cover.IntVar(&opts.DPI, "dpi", 0, "Document rendering resolution in DPI (PDF, EPUB, etc.), 0 uses the default (300)")
 	cover.StringVar(&opts.Format, "format", "jpeg", "Image format, valid values are jpeg, png, tiff, bmp, webp, avif")
 	cover.IntVar(&opts.Quality, "quality", 75, "Image quality")
 	cover.IntVar(&opts.Effort, "effort", -1, "Encoder speed/effort, format-specific (webp method 0-6, avif speed 0-10, jxl effort 1-10), -1 uses the format default")
@@ -216,6 +218,7 @@ func parseFlags() (cbconvert.Options, []string) {
 	thumbnail.IntVar(&opts.Width, "width", 0, "Image width")
 	thumbnail.IntVar(&opts.Height, "height", 0, "Image height")
 	thumbnail.BoolVar(&opts.Fit, "fit", false, "Best fit for required width and height")
+	thumbnail.IntVar(&opts.DPI, "dpi", 0, "Document rendering resolution in DPI (PDF, EPUB, etc.), 0 uses the default (300)")
 	thumbnail.IntVar(&opts.Filter, "filter", 2, "0=NearestNeighbor, 1=Box, 2=Linear, 3=MitchellNetravali, 4=CatmullRom, 6=Gaussian, 7=Lanczos")
 	thumbnail.StringVar(&opts.OutDir, "outdir", ".", "Output directory")
 	thumbnail.StringVar(&opts.OutFile, "outfile", "", "Output file")
@@ -236,7 +239,7 @@ func parseFlags() (cbconvert.Options, []string) {
 		fmt.Fprintf(os.Stderr, "Usage: %s <command> [<flags>] [file1 dir1 ... fileOrDirN]\n\n", filepath.Base(os.Args[0]))
 		fmt.Fprintf(os.Stderr, "\nCommands:\n")
 		fmt.Fprintf(os.Stderr, "\n  convert\n    \tConvert archive or document\n\n")
-		order := []string{"width", "height", "fit", "format", "archive", "zip-level", "quality", "effort", "lossless", "combine", "outfile", "filter", "no-cover", "no-rgb",
+		order := []string{"width", "height", "fit", "dpi", "format", "archive", "zip-level", "quality", "effort", "lossless", "combine", "outfile", "filter", "no-cover", "no-rgb",
 			"no-nonimage", "no-convert", "grayscale", "rotate", "brightness", "contrast", "suffix", "outdir", "size", "recursive", "quiet"}
 		for _, name := range order {
 			f := convert.Lookup(name)
@@ -244,14 +247,14 @@ func parseFlags() (cbconvert.Options, []string) {
 			fmt.Fprintf(os.Stderr, "%v (default %q)\n", f.Usage, f.DefValue)
 		}
 		fmt.Fprintf(os.Stderr, "\n  cover\n    \tExtract cover\n\n")
-		order = []string{"width", "height", "fit", "format", "quality", "effort", "lossless", "combine", "outfile", "filter", "outdir", "size", "recursive", "quiet"}
+		order = []string{"width", "height", "fit", "dpi", "format", "quality", "effort", "lossless", "filter", "outdir", "size", "recursive", "quiet"}
 		for _, name := range order {
 			f := cover.Lookup(name)
 			fmt.Fprintf(os.Stderr, "    --%s\n    \t", f.Name)
 			fmt.Fprintf(os.Stderr, "%v (default %q)\n", f.Usage, f.DefValue)
 		}
 		fmt.Fprintf(os.Stderr, "\n  thumbnail\n    \tExtract cover thumbnail (freedesktop spec.)\n\n")
-		order = []string{"width", "height", "fit", "filter", "outdir", "outfile", "size", "recursive", "quiet"}
+		order = []string{"width", "height", "fit", "dpi", "filter", "outdir", "outfile", "size", "recursive", "quiet"}
 		for _, name := range order {
 			f := thumbnail.Lookup(name)
 			fmt.Fprintf(os.Stderr, "    --%s\n    \t", f.Name)