From 09630243fb33dcf9868bf4dc31c693684807cd82 Mon Sep 17 00:00:00 2001
From: Milan Nikolic <gen2brain@gmail.com>
Date: Tue, 23 Jun 2026 04:39:03 +0200
Subject: [PATCH] Fix 4-bit 16 color palette

---
 cbconvert.go         |  4 ++--
 cbconvert_archive.go |  2 +-
 cbconvert_func.go    |  2 +-
 cbconvert_image.go   | 38 +++++++++++++++++++-------------------
 4 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/cbconvert.go b/cbconvert.go
index cfda7ca..4523d03 100644
--- a/cbconvert.go
+++ b/cbconvert.go
@@ -87,7 +87,7 @@ type Converter struct {
 	Workdir string
 	// Number of files
 	Nfiles int
-	// Index of current file
+	// Index of the current file
 	CurrFile int
 	// Number of contents in archive/document
 	Ncontents int
@@ -486,7 +486,7 @@ func (c *Converter) Preview(fileName string, fileInfo os.FileInfo, width, height
 	return img, nil
 }
 
-// Convert converts comic book.
+// Convert converts a comic book.
 func (c *Converter) Convert(fileName string, fileInfo os.FileInfo) error {
 	c.CurrFile++
 
diff --git a/cbconvert_archive.go b/cbconvert_archive.go
index 763a303..4928d3f 100644
--- a/cbconvert_archive.go
+++ b/cbconvert_archive.go
@@ -336,7 +336,7 @@ func (c *Converter) archiveSetComment(fileName, commentBody string) error {
 	return nil
 }
 
-// archiveFileAdd adds file to archive.
+// archiveFileAdd adds a file to the archive.
 func (c *Converter) archiveFileAdd(fileName, newFileName string) error {
 	zr, err := zip.OpenReader(fileName)
 	if err != nil {
diff --git a/cbconvert_func.go b/cbconvert_func.go
index 43b76b3..b9917d2 100644
--- a/cbconvert_func.go
+++ b/cbconvert_func.go
@@ -59,7 +59,7 @@ func imagesFromSlice(files []string) []string {
 	return images
 }
 
-// isArchive checks if file is archive.
+// isArchive checks if a file is archive.
 func isArchive(f string) bool {
 	var types = []string{".rar", ".zip", ".7z", ".tar", ".cbr", ".cbz", ".cb7", ".cbt"}
 	for _, t := range types {
diff --git a/cbconvert_image.go b/cbconvert_image.go
index 3e65a3d..94bda06 100644
--- a/cbconvert_image.go
+++ b/cbconvert_image.go
@@ -22,7 +22,7 @@ const (
 	mitchellNetravali
 	// CatmullRom is a sharp bicubic filter.
 	catmullRom
-	// Gaussian is a blurring filter that uses gaussian function, useful for noise removal.
+	// Gaussian is a blurring filter, which uses gaussian function, useful for noise removal.
 	gaussian
 	// Lanczos is a high-quality resampling filter, it's slower than cubic filters.
 	lanczos
@@ -124,7 +124,7 @@ func imageToGray(src image.Image) *image.Gray {
 	return dst
 }
 
-// isGrayScale checks if image is grayscale.
+// isGrayScale checks if the image is grayscale.
 func isGrayScale(img image.Image) bool {
 	model := img.ColorModel()
 	if model == color.GrayModel || model == color.Gray16Model {
@@ -135,29 +135,29 @@ func isGrayScale(img image.Image) bool {
 }
 
 var colors16 = []color.Color{
-	color.RGBA{0, 0, 0, 255},
-	color.RGBA{17, 17, 17, 255},
-	color.RGBA{34, 34, 34, 255},
-	color.RGBA{51, 51, 51, 255},
-	color.RGBA{68, 68, 68, 255},
-	color.RGBA{85, 85, 85, 255},
-	color.RGBA{102, 102, 102, 255},
-	color.RGBA{119, 119, 119, 255},
-	color.RGBA{136, 136, 136, 255},
-	color.RGBA{153, 153, 153, 255},
-	color.RGBA{170, 170, 170, 255},
-	color.RGBA{187, 187, 187, 255},
-	color.RGBA{204, 204, 204, 255},
-	color.RGBA{221, 221, 221, 255},
-	color.RGBA{238, 238, 238, 255},
-	color.RGBA{255, 255, 255, 255},
+	color.RGBA{A: 255},
+	color.RGBA{R: 17, G: 17, B: 17, A: 255},
+	color.RGBA{R: 34, G: 34, B: 34, A: 255},
+	color.RGBA{R: 51, G: 51, B: 51, A: 255},
+	color.RGBA{R: 68, G: 68, B: 68, A: 255},
+	color.RGBA{R: 85, G: 85, B: 85, A: 255},
+	color.RGBA{R: 102, G: 102, B: 102, A: 255},
+	color.RGBA{R: 119, G: 119, B: 119, A: 255},
+	color.RGBA{R: 136, G: 136, B: 136, A: 255},
+	color.RGBA{R: 153, G: 153, B: 153, A: 255},
+	color.RGBA{R: 170, G: 170, B: 170, A: 255},
+	color.RGBA{R: 187, G: 187, B: 187, A: 255},
+	color.RGBA{R: 204, G: 204, B: 204, A: 255},
+	color.RGBA{R: 221, G: 221, B: 221, A: 255},
+	color.RGBA{R: 238, G: 238, B: 238, A: 255},
+	color.RGBA{R: 255, G: 255, B: 255, A: 255},
 }
 
 // imageToPaletted converts an image.Image to *image.Paletted using 16-color palette.
 func imageToPaletted(src image.Image) *image.Paletted {
 	b := src.Bounds()
 	dst := image.NewPaletted(b, colors16)
-	draw.Draw(dst, dst.Bounds(), src, b.Min, draw.Src)
+	draw.FloydSteinberg.Draw(dst, b, imageToGray(src), b.Min)
 
 	return dst
 }