Optimize cover preview

cbconvert.go

@@ -102,6 +102,8 @@ type Converter struct {
 	prefix string
 	// Input root for the current file, used to build recursive output paths
 	root string
+	// Target size for fast previews; when set, JPEG covers are IDCT-downscaled while decoding
+	previewWidth, previewHeight int
 	// Number of files
 	Nfiles int
 	// Index of the current file
@@ -554,6 +556,27 @@ func (c *Converter) Preview(fileName string, fileInfo os.FileInfo, width, height
 	return c.previewImage(fileName, i, width, height)
 }
 
+// CoverPreview returns the cover fitted into width x height, skipping the output-codec round-trip.
+func (c *Converter) CoverPreview(fileName string, fileInfo os.FileInfo, width, height int) (Image, error) {
+	c.previewWidth, c.previewHeight = width, height
+
+	i, err := c.coverImage(fileName, fileInfo)
+	if err != nil {
+		return Image{}, fmt.Errorf("%s: %w", fileName, err)
+	}
+
+	if width != 0 && height != 0 {
+		i = fit(i, width, height, resampleFilter(c.Opts.Filter))
+	}
+
+	var img Image
+	img.Image = i
+	img.Width = i.Bounds().Dx()
+	img.Height = i.Bounds().Dy()
+
+	return img, nil
+}
+
 // PreviewPage returns the page-th image (0-based) as an image preview.
 func (c *Converter) PreviewPage(fileName string, fileInfo os.FileInfo, page, width, height int) (Image, error) {
 	i, err := c.pageImage(fileName, fileInfo, page)

cbconvert_convert.go

@@ -1,6 +1,7 @@
 package cbconvert
 
 import (
+	"bufio"
 	"bytes"
 	"context"
 	"fmt"
@@ -16,6 +17,7 @@ import (
 	"github.com/gen2brain/avif"
 	"github.com/gen2brain/go-fitz"
 	"github.com/gen2brain/jpegli"
+	"github.com/gen2brain/jpegn"
 	"github.com/gen2brain/jpegxl"
 	"github.com/gen2brain/webp"
 	"github.com/jsummers/gobmp"
@@ -356,8 +358,42 @@ func (c *Converter) imageTransform(img image.Image) image.Image {
 }
 
 // imageDecode decodes image from reader.
+// jpegnOptions decodes straight to RGBA with high-quality chroma upsampling.
+var jpegnOptions = jpegn.Options{ToRGBA: true, UpsampleMethod: jpegn.CatmullRom}
+
 func (c *Converter) imageDecode(reader io.Reader) (image.Image, error) {
-	img, _, err := image.Decode(reader)
+	br := bufio.NewReader(reader)
+
+	if magic, err := br.Peek(2); err == nil && magic[0] == 0xff && magic[1] == 0xd8 {
+		opts := jpegnOptions
+
+		if c.previewWidth > 0 && c.previewHeight > 0 {
+			data, err := io.ReadAll(br)
+			if err != nil {
+				return nil, fmt.Errorf("imageDecode: %w", err)
+			}
+
+			if cfg, err := jpegn.DecodeConfig(bytes.NewReader(data)); err == nil {
+				opts.ScaleDenom = scaleDenom(cfg.Width, cfg.Height, c.previewWidth, c.previewHeight)
+			}
+
+			img, err := jpegn.Decode(bytes.NewReader(data), &opts)
+			if err != nil {
+				return nil, fmt.Errorf("imageDecode: %w", err)
+			}
+
+			return img, nil
+		}
+
+		img, err := jpegn.Decode(br, &opts)
+		if err != nil {
+			return nil, fmt.Errorf("imageDecode: %w", err)
+		}
+
+		return img, nil
+	}
+
+	img, _, err := image.Decode(br)
 	if err != nil {
 		return img, fmt.Errorf("imageDecode: %w", err)
 	}
@@ -365,6 +401,17 @@ func (c *Converter) imageDecode(reader io.Reader) (image.Image, error) {
 	return img, nil
 }
 
+// scaleDenom returns the largest JPEG IDCT denominator (1, 2, 4, 8) that keeps w x h at or above tw x th.
+func scaleDenom(w, h, tw, th int) int {
+	for _, d := range []int{8, 4, 2} {
+		if w/d >= tw && h/d >= th {
+			return d
+		}
+	}
+
+	return 1
+}
+
 // imageEncode encodes image to file.
 func (c *Converter) imageEncode(img image.Image, w io.Writer) error {
 	var err error

cmd/cbconvert-gui/dialogs.go

@@ -70,10 +70,37 @@ func fileDlg(title string, multiple, directory bool, dirKey string) ([]string, e
 
 const dlgPreviewName = "_FILEDLGPREVIEW_"
 
+// previewPad insets the cover from the preview pane edges, in pixels per side.
+const previewPad = 8
+
 // previewCover returns a FILE_CB handler that draws the highlighted comic's cover in the dialog preview pane.
+// Extracted covers are cached by path so re-highlighting a file doesn't re-extract it.
 func previewCover() iup.FileFunc {
-	var image iup.Ihandle
-	var lastFile string
+	const maxCache = 32
+
+	cache := make(map[string]iup.Ihandle)
+	order := make([]string, 0, maxCache)
+
+	cover := func(path string, w, h int) iup.Ihandle {
+		if img, ok := cache[path]; ok {
+			return img
+		}
+
+		img := loadCover(path, w, h)
+		cache[path] = img
+		order = append(order, path)
+
+		if len(order) > maxCache {
+			old := order[0]
+			order = order[1:]
+			if oi := cache[old]; oi != 0 {
+				oi.Destroy()
+			}
+			delete(cache, old)
+		}
+
+		return img
+	}
 
 	return func(ih iup.Ihandle, filename, status string) int {
 		switch status {
@@ -82,19 +109,8 @@ func previewCover() iup.FileFunc {
 			cw, ch := iup.DrawGetSize(ih)
 			iup.DrawParentBackground(ih)
 
-			if filename != lastFile {
-				lastFile = filename
-				if image != 0 {
-					image.Destroy()
-					image = 0
-				}
-				if img := loadCover(filename, cw, ch); img != 0 {
-					image = img
-					iup.SetHandle(dlgPreviewName, image)
-				}
-			}
-
-			if image != 0 {
+			if image := cover(filename, cw-2*previewPad, ch-2*previewPad); image != 0 {
+				iup.SetHandle(dlgPreviewName, image)
 				iw, iih, _ := iup.DrawGetImageInfo(dlgPreviewName)
 				iup.DrawImage(ih, dlgPreviewName, (cw-iw)/2, (ch-iih)/2, iw, iih)
 			} else {
@@ -106,11 +122,13 @@ func previewCover() iup.FileFunc {
 
 			iup.DrawEnd(ih)
 		case "FINISH":
-			if image != 0 {
-				image.Destroy()
-				image = 0
+			for _, img := range cache {
+				if img != 0 {
+					img.Destroy()
+				}
 			}
-			lastFile = ""
+			cache = make(map[string]iup.Ihandle)
+			order = order[:0]
 		}
 
 		return iup.DEFAULT
@@ -131,7 +149,7 @@ func loadCover(path string, w, h int) iup.Ihandle {
 	opts := cbconvert.NewOptions()
 	opts.DPI = 96
 
-	img, err := cbconvert.New(opts).Preview(path, fi, w, h)
+	img, err := cbconvert.New(opts).CoverPreview(path, fi, w, h)
 	if err != nil || img.Image == nil {
 		return 0
 	}

cmd/cbconvert-gui/go.mod

@@ -23,7 +23,7 @@ require (
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/ebitengine/purego v0.10.1 // indirect
 	github.com/gen2brain/avif v0.5.1 // indirect
-	github.com/gen2brain/go-fitz v1.24.15 // indirect
+	github.com/gen2brain/go-fitz v1.28.0 // indirect
 	github.com/gen2brain/jpegli v0.4.1 // indirect
 	github.com/gen2brain/jpegxl v0.5.1 // indirect
 	github.com/gen2brain/webp v0.6.1 // indirect
@@ -31,7 +31,6 @@ require (
 	github.com/golang/geo v0.0.0-20260625163123-7c0e84413537 // indirect
 	github.com/hashicorp/golang-lru/v2 v2.0.7 // indirect
 	github.com/jsummers/gobmp v0.0.0-20230614200233-a9de23ed2e25 // indirect
-	github.com/jupiterrider/ffi v0.7.0 // indirect
 	github.com/klauspost/compress v1.18.6 // indirect
 	github.com/klauspost/pgzip v1.2.6 // indirect
 	github.com/mholt/archives v0.1.5 // indirect

cmd/cbconvert-gui/go.sum

@@ -42,8 +42,7 @@ github.com/gen2brain/avif v0.5.1 h1:LQzLsJpWyGlsa4wuZ3D57qEbCiICIK7Yidz5ZPEwzTk=
 github.com/gen2brain/avif v0.5.1/go.mod h1:QgrYqdVE9y40PCfArK9VakcMIpYeDYpZmCSLkW6C1n8=
 github.com/gen2brain/cbconvert v1.0.5-0.20260626071631-8155626dbb42 h1:p1K1jOk+rKDhTgh6fiYMKSqXJdIVUWFLK5jodTtwPOU=
 github.com/gen2brain/cbconvert v1.0.5-0.20260626071631-8155626dbb42/go.mod h1:qHzMhKZ7VBTffwDQ/9rc4yZ9FO5677ZSjSFZ7QNfaLw=
-github.com/gen2brain/go-fitz v1.24.15 h1:sJNB1MOWkqnzzENPHggFpgxTwW0+S5WF/rM5wUBpJWo=
-github.com/gen2brain/go-fitz v1.24.15/go.mod h1:SftkiVbTHqF141DuiLwBBM65zP7ig6AVDQpf2WlHamo=
+github.com/gen2brain/go-fitz v1.28.0 h1:RovqgQPAcOuyv5HZrWsTWl8qwlwbAHSKcAZXZUw0Vlk=
 github.com/gen2brain/iup-go/iup v0.32.1-0.20260626100855-f328861e3291 h1:ad/nhBGhknOGDpiHnQ0ZLltZccG82t4tAKK94SrQ8OY=
 github.com/gen2brain/iup-go/iup v0.32.1-0.20260626100855-f328861e3291/go.mod h1:V4f7tHOJAeHtjQ+ju795QKv6DGdLEb4L5cmWB1sjSzU=
 github.com/gen2brain/jpegli v0.4.1 h1:qc11IQU0jTYFltroulT4MXmbu9YRftqHV0YBZ0Bqz5o=
@@ -69,8 +68,6 @@ github.com/hashicorp/golang-lru/v2 v2.0.7/go.mod h1:QeFd9opnmA6QUJc5vARoKUSoFhyf
 github.com/jessevdk/go-flags v1.4.0/go.mod h1:4FA24M0QyGHXBuZZK/XkWh8h0e1EYbRYJSGM75WSRxI=
 github.com/jsummers/gobmp v0.0.0-20230614200233-a9de23ed2e25 h1:YLvr1eE6cdCqjOe972w/cYF+FjW34v27+9Vo5106B4M=
 github.com/jsummers/gobmp v0.0.0-20230614200233-a9de23ed2e25/go.mod h1:kLgvv7o6UM+0QSf0QjAse3wReFDsb9qbZJdfexWlrQw=
-github.com/jupiterrider/ffi v0.7.0 h1:RKsl6Ascal+3kyAqR5Qcbp83LceQMLc1VZbPfHWoNzs=
-github.com/jupiterrider/ffi v0.7.0/go.mod h1:9dauhpOfNqrqk28fxuu0kkdeFtT9Qr4vbfigiuIXN7c=
 github.com/klauspost/compress v1.4.1/go.mod h1:RyIbtBH6LamlWaDj8nUwkbUhJ87Yi3uG0guNDohfE1A=
 github.com/klauspost/compress v1.18.6 h1:2jupLlAwFm95+YDR+NwD2MEfFO9d4z4Prjl1XXDjuao=
 github.com/klauspost/compress v1.18.6/go.mod h1:cwPg85FWrGar70rWktvGQj8/hthj3wpl0PGDogxkrSQ=

cmd/cbconvert-gui/settings.go

@@ -148,6 +148,8 @@ func settingsApply(group string) {
 		}
 	}
 
+	userLossless = iup.GetHandle("Lossless").GetAttribute("VALUE") == "ON"
+
 	syncLabels()
 	setActive()
 	previewPost()

cmd/cbconvert-gui/state.go

@@ -1,10 +1,40 @@
 package main
 
 import (
+	"runtime/debug"
+	"strings"
+
 	"github.com/gen2brain/cbconvert/cmd/cbconvert-gui/i18n"
 	"github.com/gen2brain/iup-go/iup"
 )
 
+// jxlLosslessBuild reports whether wasm2go and nodynamic leave zune-jpegxl (lossless-only) as the only jxl encoder.
+var jxlLosslessBuild = func() bool {
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		return false
+	}
+	var wasm2go, nodynamic bool
+	for _, kv := range info.Settings {
+		if kv.Key != "-tags" {
+			continue
+		}
+		for _, t := range strings.Split(kv.Value, ",") {
+			switch t {
+			case "wasm2go":
+				wasm2go = true
+			case "nodynamic":
+				nodynamic = true
+			}
+		}
+	}
+	return wasm2go && nodynamic
+}()
+
+// userLossless is the user's Lossless preference, tracked separately because a jxl
+// wasm2go build force-sets the widget on.
+var userLossless bool
+
 func setActive() {
 	if busy {
 		return
@@ -68,7 +98,15 @@ func setActive() {
 	}
 
 	canLossless := opts.Format == "webp" || opts.Format == "avif" || opts.Format == "jxl"
-	losslessOn := canLossless && opts.Lossless
+	jxlLossless := jxlLosslessBuild && opts.Format == "jxl"
+
+	// jxl wasm2go forces lossless on; otherwise show the user's preference so it doesn't stay stuck on.
+	losslessVal := "OFF"
+	if jxlLossless || userLossless {
+		losslessVal = "ON"
+	}
+	iup.GetHandle("Lossless").SetAttribute("VALUE", losslessVal)
+	losslessOn := jxlLossless || (canLossless && userLossless)
 
 	if (opts.Format == "jpeg" || canLossless) && !opts.NoConvert && !losslessOn {
 		iup.GetHandle("VboxQuality").SetAttribute("ACTIVE", "YES")
@@ -84,6 +122,11 @@ func setActive() {
 		iup.GetHandle("Lossless").SetAttribute("ACTIVE", "NO")
 	}
 
+	if jxlLossless {
+		iup.GetHandle("Lossless").SetAttribute("ACTIVE", "NO")
+		iup.GetHandle("VboxEffort").SetAttribute("ACTIVE", "NO")
+	}
+
 	if opts.Width != 0 && opts.Height != 0 && !opts.NoConvert {
 		iup.GetHandle("Fit").SetAttribute("ACTIVE", "YES")
 	} else {

cmd/cbconvert-gui/widgets.go

@@ -60,7 +60,7 @@ func list() iup.Ihandle {
 		"TITLE1":         i18n.Lng(i18n.ColTitle),
 		"TITLE2":         i18n.Lng(i18n.ColType),
 		"TITLE3":         i18n.Lng(i18n.ColSize),
-		"WIDTH1":         "300",
+		"WIDTH1":         "250",
 		"WIDTH2":         "50",
 		"WIDTH3":         "100",
 		"ALIGNMENT2":     "ACENTER",
@@ -568,6 +568,7 @@ func tabImage() iup.Ihandle {
 				iup.Toggle(i18n.Lng(i18n.TglLossless)).SetHandle("Lossless").
 					SetAttribute("TIP", i18n.Lng(i18n.TipLossless)).
 					SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+						userLossless = ih.GetAttribute("VALUE") == "ON"
 						setActive()
 						previewPost()
 

cmd/cbconvert/go.mod

@@ -24,7 +24,7 @@ require (
 	github.com/ebitengine/purego v0.10.1 // indirect
 	github.com/fvbommel/sortorder v1.1.0 // indirect
 	github.com/gen2brain/avif v0.5.1 // indirect
-	github.com/gen2brain/go-fitz v1.24.15 // indirect
+	github.com/gen2brain/go-fitz v1.28.0 // indirect
 	github.com/gen2brain/jpegli v0.4.1 // indirect
 	github.com/gen2brain/jpegxl v0.5.1 // indirect
 	github.com/gen2brain/webp v0.6.1 // indirect
@@ -32,7 +32,6 @@ require (
 	github.com/golang/geo v0.0.0-20260625163123-7c0e84413537 // indirect
 	github.com/hashicorp/golang-lru/v2 v2.0.7 // indirect
 	github.com/jsummers/gobmp v0.0.0-20230614200233-a9de23ed2e25 // indirect
-	github.com/jupiterrider/ffi v0.7.0 // indirect
 	github.com/klauspost/compress v1.18.6 // indirect
 	github.com/klauspost/pgzip v1.2.6 // indirect
 	github.com/mattn/go-runewidth v0.0.24 // indirect

cmd/cbconvert/go.sum

@@ -46,8 +46,7 @@ github.com/gen2brain/avif v0.5.1 h1:LQzLsJpWyGlsa4wuZ3D57qEbCiICIK7Yidz5ZPEwzTk=
 github.com/gen2brain/avif v0.5.1/go.mod h1:QgrYqdVE9y40PCfArK9VakcMIpYeDYpZmCSLkW6C1n8=
 github.com/gen2brain/cbconvert v1.0.5-0.20260626071631-8155626dbb42 h1:p1K1jOk+rKDhTgh6fiYMKSqXJdIVUWFLK5jodTtwPOU=
 github.com/gen2brain/cbconvert v1.0.5-0.20260626071631-8155626dbb42/go.mod h1:qHzMhKZ7VBTffwDQ/9rc4yZ9FO5677ZSjSFZ7QNfaLw=
-github.com/gen2brain/go-fitz v1.24.15 h1:sJNB1MOWkqnzzENPHggFpgxTwW0+S5WF/rM5wUBpJWo=
-github.com/gen2brain/go-fitz v1.24.15/go.mod h1:SftkiVbTHqF141DuiLwBBM65zP7ig6AVDQpf2WlHamo=
+github.com/gen2brain/go-fitz v1.28.0 h1:RovqgQPAcOuyv5HZrWsTWl8qwlwbAHSKcAZXZUw0Vlk=
 github.com/gen2brain/jpegli v0.4.1 h1:qc11IQU0jTYFltroulT4MXmbu9YRftqHV0YBZ0Bqz5o=
 github.com/gen2brain/jpegli v0.4.1/go.mod h1:zJ++s4symmKCN1CLkrY0dGXTY3s0NWbd94Rz9KLdCzk=
 github.com/gen2brain/jpegxl v0.5.1 h1:UuBUIkZ35DErImU3bTA6rltfV5zSgVNOA/K5a6JibfE=
@@ -71,8 +70,6 @@ github.com/hashicorp/golang-lru/v2 v2.0.7/go.mod h1:QeFd9opnmA6QUJc5vARoKUSoFhyf
 github.com/jessevdk/go-flags v1.4.0/go.mod h1:4FA24M0QyGHXBuZZK/XkWh8h0e1EYbRYJSGM75WSRxI=
 github.com/jsummers/gobmp v0.0.0-20230614200233-a9de23ed2e25 h1:YLvr1eE6cdCqjOe972w/cYF+FjW34v27+9Vo5106B4M=
 github.com/jsummers/gobmp v0.0.0-20230614200233-a9de23ed2e25/go.mod h1:kLgvv7o6UM+0QSf0QjAse3wReFDsb9qbZJdfexWlrQw=
-github.com/jupiterrider/ffi v0.7.0 h1:RKsl6Ascal+3kyAqR5Qcbp83LceQMLc1VZbPfHWoNzs=
-github.com/jupiterrider/ffi v0.7.0/go.mod h1:9dauhpOfNqrqk28fxuu0kkdeFtT9Qr4vbfigiuIXN7c=
 github.com/klauspost/compress v1.4.1/go.mod h1:RyIbtBH6LamlWaDj8nUwkbUhJ87Yi3uG0guNDohfE1A=
 github.com/klauspost/compress v1.18.6 h1:2jupLlAwFm95+YDR+NwD2MEfFO9d4z4Prjl1XXDjuao=
 github.com/klauspost/compress v1.18.6/go.mod h1:cwPg85FWrGar70rWktvGQj8/hthj3wpl0PGDogxkrSQ=

go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/gen2brain/avif v0.5.1
 	github.com/gen2brain/go-fitz v1.28.0
 	github.com/gen2brain/jpegli v0.4.1
+	github.com/gen2brain/jpegn v0.4.2
 	github.com/gen2brain/jpegxl v0.5.1
 	github.com/gen2brain/webp v0.6.1
 	github.com/jsummers/gobmp v0.0.0-20230614200233-a9de23ed2e25

go.sum

@@ -44,6 +44,8 @@ github.com/gen2brain/go-fitz v1.28.0 h1:RovqgQPAcOuyv5HZrWsTWl8qwlwbAHSKcAZXZUw0
 github.com/gen2brain/go-fitz v1.28.0/go.mod h1:pY2hqAjp9Zy7qfPI2gwbJMHBFAdZpVXOLrRxD82l3Bs=
 github.com/gen2brain/jpegli v0.4.1 h1:qc11IQU0jTYFltroulT4MXmbu9YRftqHV0YBZ0Bqz5o=
 github.com/gen2brain/jpegli v0.4.1/go.mod h1:zJ++s4symmKCN1CLkrY0dGXTY3s0NWbd94Rz9KLdCzk=
+github.com/gen2brain/jpegn v0.4.2 h1:sxy2yolV1eNA02uYtnqBFm4EIC3ETnars98aG7Dc4LM=
+github.com/gen2brain/jpegn v0.4.2/go.mod h1:YvcVOmVPSAsefH6yn9HBW3uY0EHlZwCMoiJXoAWfgL0=
 github.com/gen2brain/jpegxl v0.5.1 h1:UuBUIkZ35DErImU3bTA6rltfV5zSgVNOA/K5a6JibfE=
 github.com/gen2brain/jpegxl v0.5.1/go.mod h1:Wlc6lqx03RJfhiQRyHa2e+8VQwT4/qv7zSRsNv9T+yE=
 github.com/gen2brain/webp v0.6.1 h1:ei7Y1SWpQcdqz3YNDNyn4y2nQanxs9WLzwW5/2DKS64=

go.work.sum

@@ -95,6 +95,7 @@ golang.org/x/mod v0.36.0 h1:JJjpVx6myfUsUdAzZuOSTTmRE0PfZeNWzzvKrP7amb4=
 golang.org/x/mod v0.36.0/go.mod h1:moc6ELqsWcOw5Ef3xVprK5ul/MvtVvkIXLziUOICjUQ=
 golang.org/x/oauth2 v0.34.0 h1:hqK/t4AKgbqWkdkcAeI8XLmbK+4m4G5YeQRrmiotGlw=
 golang.org/x/oauth2 v0.34.0/go.mod h1:lzm5WQJQwKZ3nwavOZ3IS5Aulzxi68dUSgRHujetwEA=
+golang.org/x/sys v0.33.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
 golang.org/x/time v0.14.0 h1:MRx4UaLrDotUKUdCIqzPC48t1Y9hANFKIRpNx+Te8PI=
 golang.org/x/time v0.14.0/go.mod h1:eL/Oa2bBBK0TkX57Fyni+NgnyQQN4LitPmob2Hjnqw4=
 golang.org/x/tools v0.45.0 h1:18qN3FAooORvApf5XjCXgsuayZOEtXf6JK18I3+ONa8=