support grayscale or color mode

grayscale is on by default
as the conversion is mainly
useful for eInk device.

internal/converter/converter.go

@@ -14,6 +14,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"regexp"
 	"runtime"
 	"strings"
 	"time"
@@ -100,6 +101,7 @@ func (c *Converter) InitParse() {
 	c.AddSection("Config")
 	c.AddStringParam(&c.Options.Profile, "profile", c.Options.Profile, fmt.Sprintf("Profile to use: \n%s", c.Options.AvailableProfiles()))
 	c.AddIntParam(&c.Options.Quality, "quality", c.Options.Quality, "Quality of the image")
+	c.AddBoolParam(&c.Options.Grayscale, "grayscale", c.Options.Grayscale, "Grayscale image. Ideal for eInk devices.")
 	c.AddBoolParam(&c.Options.Crop, "crop", c.Options.Crop, "Crop images")
 	c.AddIntParam(&c.Options.CropRatioLeft, "crop-ratio-left", c.Options.CropRatioLeft, "Crop ratio left: ratio of pixels allow to be non blank while cutting on the left.")
 	c.AddIntParam(&c.Options.CropRatioUp, "crop-ratio-up", c.Options.CropRatioUp, "Crop ratio up: ratio of pixels allow to be non blank while cutting on the top.")
@@ -116,6 +118,8 @@ func (c *Converter) InitParse() {
 	c.AddIntParam(&c.Options.LimitMb, "limitmb", c.Options.LimitMb, "Limit size of the EPUB: Default nolimit (0), Minimum 20")
 	c.AddBoolParam(&c.Options.StripFirstDirectoryFromToc, "strip", c.Options.StripFirstDirectoryFromToc, "Strip first directory from the TOC if only 1")
 	c.AddIntParam(&c.Options.SortPathMode, "sort", c.Options.SortPathMode, "Sort path mode\n0 = alpha for path and file\n1 = alphanum for path and alpha for file\n2 = alphanum for path and file")
+	c.AddStringParam(&c.Options.ForegroundColor, "foreground-color", c.Options.ForegroundColor, "Foreground color in hexa format RGB. Black=000, White=FFF")
+	c.AddStringParam(&c.Options.BackgroundColor, "background-color", c.Options.BackgroundColor, "Background color in hexa format RGB. Black=000, White=FFF, Light Gray=DDD, Dark Gray=777")
 
 	c.AddSection("Default config")
 	c.AddBoolParam(&c.Options.Show, "show", false, "Show your default parameters")
@@ -293,6 +297,16 @@ func (c *Converter) Validate() error {
 		return errors.New("sort should be 0, 1 or 2")
 	}
 
+	// Color
+	colorRegex := regexp.MustCompile("^[0-9A-F]{3}$")
+	if !colorRegex.MatchString(c.Options.ForegroundColor) {
+		return errors.New("foreground color must have color format in hexa: [0-9A-F]{3}")
+	}
+
+	if !colorRegex.MatchString(c.Options.BackgroundColor) {
+		return errors.New("background color must have color format in hexa: [0-9A-F]{3}")
+	}
+
 	return nil
 }
 

internal/converter/options/converter_options.go

@@ -23,6 +23,7 @@ type Options struct {
 	// Config
 	Profile                    string `yaml:"profile"`
 	Quality                    int    `yaml:"quality"`
+	Grayscale                  bool   `yaml:"grayscale"`
 	Crop                       bool   `yaml:"crop"`
 	CropRatioLeft              int    `yaml:"crop_ratio_left"`
 	CropRatioUp                int    `yaml:"crop_ratio_up"`
@@ -39,6 +40,8 @@ type Options struct {
 	LimitMb                    int    `yaml:"limit_mb"`
 	StripFirstDirectoryFromToc bool   `yaml:"strip_first_directory_from_toc"`
 	SortPathMode               int    `yaml:"sort_path_mode"`
+	ForegroundColor            string `yaml:"foreground_color"`
+	BackgroundColor            string `yaml:"background_color"`
 
 	// Default Config
 	Show  bool `yaml:"-"`
@@ -62,6 +65,7 @@ func New() *Options {
 	return &Options{
 		Profile:                    "",
 		Quality:                    85,
+		Grayscale:                  true,
 		Crop:                       true,
 		CropRatioLeft:              1,
 		CropRatioUp:                1,
@@ -77,32 +81,34 @@ func New() *Options {
 		LimitMb:                    0,
 		StripFirstDirectoryFromToc: false,
 		SortPathMode:               1,
+		ForegroundColor:            "000",
+		BackgroundColor:            "FFF",
 		profiles:                   profiles.New(),
 	}
 }
 
 func (o *Options) Header() string {
-	return `Go Comic Converter
+	return "Go Comic Converter\n\nOptions:"
-
-Options:`
 }
 
 func (o *Options) String() string {
-	return fmt.Sprintf(`%s
+	var b strings.Builder
-    Input                     : %s
+	b.WriteString(o.Header())
-    Output                    : %s
+	for _, v := range []struct {
-    Author                    : %s
+		K string
-    Title                     : %s
+		V any
-    Workers                   : %d%s
+	}{
-`,
+		{"Input", o.Input},
-		o.Header(),
+		{"Output", o.Output},
-		o.Input,
+		{"Author", o.Author},
-		o.Output,
+		{"Title", o.Title},
-		o.Author,
+		{"Workers", o.Workers},
-		o.Title,
+	} {
-		o.Workers,
+		b.WriteString(fmt.Sprintf("\n    %-26s: %v", v.K, v.V))
-		o.ShowConfig(),
+	}
-	)
+	b.WriteString(o.ShowConfig())
+	b.WriteRune('\n')
+	return b.String()
 }
 
 // Config file: ~/.go-comic-converter.yaml
@@ -161,40 +167,34 @@ func (o *Options) ShowConfig() string {
 		sortpathmode = "path=alphanum, file=alphanum"
 	}
 
-	return fmt.Sprintf(`
+	var b strings.Builder
-    Profile                   : %s
+	for _, v := range []struct {
-    ViewRatio                 : 1:%s
+		K string
-    View                      : %s
+		V any
-    Quality                   : %d
+	}{
-    Crop                      : %v
+		{"Profile", profileDesc},
-    CropRatio                 : %d Left - %d Up - %d Right - %d Bottom
+		{"ViewRatio", fmt.Sprintf("1:%s", strings.TrimRight(fmt.Sprintf("%f", profiles.PerfectRatio), "0"))},
-    Brightness                : %d
+		{"View", viewDesc},
-    Contrast                  : %d
+		{"Quality", o.Quality},
-    AutoRotate                : %v
+		{"Grayscale", o.Grayscale},
-    AutoSplitDoublePage       : %v
+		{"Crop", o.Crop},
-    NoBlankImage              : %v
+		{"CropRatio", fmt.Sprintf("%d Left - %d Up - %d Right - %d Bottom", o.CropRatioLeft, o.CropRatioUp, o.CropRatioRight, o.CropRatioBottom)},
-    Manga                     : %v
+		{"Brightness", o.Brightness},
-    HasCover                  : %v
+		{"Contrast", o.Contrast},
-    LimitMb                   : %s
+		{"AutoRotate", o.AutoRotate},
-    StripFirstDirectoryFromToc: %v
+		{"AutoSplitDoublePage", o.AutoSplitDoublePage},
-    SortPathMode              : %s`,
+		{"NoBlankImage", o.NoBlankImage},
-		profileDesc,
+		{"Manga", o.Manga},
-		strings.TrimRight(fmt.Sprintf("%f", profiles.PerfectRatio), "0"),
+		{"HasCover", o.HasCover},
-		viewDesc,
+		{"LimitMb", limitmb},
-		o.Quality,
+		{"StripFirstDirectoryFromToc", o.StripFirstDirectoryFromToc},
-		o.Crop,
+		{"SortPathMode", sortpathmode},
-		o.CropRatioLeft, o.CropRatioUp, o.CropRatioRight, o.CropRatioBottom,
+		{"Foreground Color", fmt.Sprintf("#%s", o.ForegroundColor)},
-		o.Brightness,
+		{"Background Color", fmt.Sprintf("#%s", o.BackgroundColor)},
-		o.Contrast,
+	} {
-		o.AutoRotate,
+		b.WriteString(fmt.Sprintf("\n    %-26s: %v", v.K, v.V))
-		o.AutoSplitDoublePage,
+	}
-		o.NoBlankImage,
+	return b.String()
-		o.Manga,
-		o.HasCover,
-		limitmb,
-		o.StripFirstDirectoryFromToc,
-		sortpathmode,
-	)
 }
 
 // reset all settings to default value

internal/converter/profiles/converter_profiles.go

@@ -16,7 +16,7 @@ type Profile struct {
 }
 
 // Recommended ratio of image for perfect rendering Portrait or Landscape.
-const PerfectRatio = 1.5
+const PerfectRatio = 1.6
 
 // Compute best dimension based on device size
 func (p Profile) PerfectDim() (int, int) {
@@ -60,6 +60,8 @@ func New() Profiles {
 		{"KoF", "Kobo Forma", 1440, 1920},
 		{"KoS", "Kobo Sage", 1440, 1920},
 		{"KoE", "Kobo Elipsa", 1404, 1872},
+		// High Resolution for Tablette
+		{"HR", "High Resolution", 2400, 3840},
 	}
 }
 

internal/epub/epub.go

@@ -77,7 +77,7 @@ func (e *ePub) writeImage(wz *epubzip.EPUBZip, img *epubimage.Image, zipImg *zip
 			"Title":      fmt.Sprintf("Image %d Part %d", img.Id, img.Part),
 			"ViewPort":   fmt.Sprintf("width=%d,height=%d", e.Image.View.Width, e.Image.View.Height),
 			"ImagePath":  img.ImgPath(),
-			"ImageStyle": img.ImgStyle(e.Image.View.Width, e.Image.View.Height, e.Image.Manga),
+			"ImageStyle": img.ImgStyle(e.Image.View.Width, e.Image.View.Height, ""),
 		})),
 	)
 	if err == nil {
@@ -251,6 +251,10 @@ func (e *ePub) Write() error {
 		if totalParts > 1 {
 			title = fmt.Sprintf("%s [%d/%d]", title, i+1, totalParts)
 		}
+		titleAlign := "left:0"
+		if e.Image.Manga {
+			titleAlign = "right:0"
+		}
 
 		content := []zipContent{
 			{"META-INF/container.xml", epubtemplates.Container},
@@ -269,8 +273,7 @@ func (e *ePub) Write() error {
 			})},
 			{"OEBPS/toc.xhtml", epubtemplates.Toc(title, e.StripFirstDirectoryFromToc, part.Images)},
 			{"OEBPS/Text/style.css", e.render(epubtemplates.Style, map[string]any{
-				"PageWidth":  e.Image.View.Width,
+				"View": e.Image.View,
-				"PageHeight": e.Image.View.Height,
 			})},
 			{"OEBPS/Text/space_title.xhtml", e.render(epubtemplates.Blank, map[string]any{
 				"Title":    "Blank Page Title",
@@ -280,7 +283,7 @@ func (e *ePub) Write() error {
 				"Title":      title,
 				"ViewPort":   fmt.Sprintf("width=%d,height=%d", e.Image.View.Width, e.Image.View.Height),
 				"ImagePath":  "Images/title.jpg",
-				"ImageStyle": part.Cover.ImgStyle(e.Image.View.Width, e.Image.View.Height, e.Image.Manga),
+				"ImageStyle": part.Cover.ImgStyle(e.Image.View.Width, e.Image.View.Height, titleAlign),
 			})},
 		}
 

internal/epub/image/epub_image.go

@@ -19,6 +19,7 @@ type Image struct {
 	DoublePage bool
 	Path       string
 	Name       string
+	Position   string
 }
 
 // key name of the blank plage after the image
@@ -70,24 +71,17 @@ func (i *Image) EPUBImgPath() string {
 //
 // center by default.
 // align to left or right if it's part of the splitted double page.
-func (i *Image) ImgStyle(viewWidth, viewHeight int, manga bool) string {
+func (i *Image) ImgStyle(viewWidth, viewHeight int, align string) string {
 	marginW, marginH := float64(viewWidth-i.Width)/2, float64(viewHeight-i.Height)/2
-	left, top := marginW*100/float64(viewWidth), marginH*100/float64(viewHeight)
+
-	var align string
+	if align == "" {
-	switch i.Part {
+		switch i.Position {
-	case 0:
+		case "rendition:page-spread-left":
-		align = fmt.Sprintf("left:%.2f%%", left)
-	case 1:
-		if manga {
-			align = "left:0"
-		} else {
 			align = "right:0"
-		}
+		case "rendition:page-spread-right":
-	case 2:
-		if manga {
-			align = "right:0"
-		} else {
 			align = "left:0"
+		default:
+			align = fmt.Sprintf("left:%.2f%%", marginW*100/float64(viewWidth))
 		}
 	}
 
@@ -95,7 +89,7 @@ func (i *Image) ImgStyle(viewWidth, viewHeight int, manga bool) string {
 		"width:%dpx; height:%dpx; top:%.2f%%; %s;",
 		i.Width,
 		i.Height,
-		top,
+		marginH*100/float64(viewHeight),
 		align,
 	)
 }

internal/epub/imageprocessor/epub_image_processor.go

@@ -6,6 +6,7 @@ package epubimageprocessor
 import (
 	"fmt"
 	"image"
+	"image/draw"
 	"os"
 	"sync"
 
@@ -126,6 +127,37 @@ func (e *EPUBImageProcessor) Load() (images []*epubimage.Image, err error) {
 	return images, nil
 }
 
+func (e *EPUBImageProcessor) createImage(src image.Image, r image.Rectangle) draw.Image {
+	if e.Options.Image.GrayScale {
+		return image.NewGray(r)
+	}
+
+	switch t := src.(type) {
+	case *image.Gray:
+		return image.NewGray(r)
+	case *image.Gray16:
+		return image.NewGray16(r)
+	case *image.RGBA:
+		return image.NewRGBA(r)
+	case *image.RGBA64:
+		return image.NewRGBA64(r)
+	case *image.NRGBA:
+		return image.NewNRGBA(r)
+	case *image.NRGBA64:
+		return image.NewNRGBA64(r)
+	case *image.Alpha:
+		return image.NewAlpha(r)
+	case *image.Alpha16:
+		return image.NewAlpha16(r)
+	case *image.CMYK:
+		return image.NewCMYK(r)
+	case *image.Paletted:
+		return image.NewPaletted(r, t.Palette)
+	default:
+		return image.NewNRGBA64(r)
+	}
+}
+
 // transform image into 1 or 3 images
 // only doublepage with autosplit has 3 versions
 func (e *EPUBImageProcessor) transformImage(src image.Image, srcId int) []image.Image {
@@ -177,7 +209,7 @@ func (e *EPUBImageProcessor) transformImage(src image.Image, srcId int) []image.
 	// convert
 	{
 		g := gift.New(filters...)
-		dst := image.NewGray(g.Bounds(src.Bounds()))
+		dst := e.createImage(src, g.Bounds(src.Bounds()))
 		g.Draw(dst, src)
 		images = append(images, dst)
 	}
@@ -204,7 +236,7 @@ func (e *EPUBImageProcessor) transformImage(src image.Image, srcId int) []image.
 			epubimagefilters.CropSplitDoublePage(b),
 			epubimagefilters.Resize(e.Image.View.Width, e.Image.View.Height, gift.LanczosResampling),
 		)
-		dst := image.NewGray(g.Bounds(src.Bounds()))
+		dst := e.createImage(src, g.Bounds(src.Bounds()))
 		g.Draw(dst, src)
 		images = append(images, dst)
 	}
@@ -213,11 +245,11 @@ func (e *EPUBImageProcessor) transformImage(src image.Image, srcId int) []image.
 }
 
 // create a title page with the cover
-func (e *EPUBImageProcessor) CoverTitleData(img image.Image, title string) (*epubzip.ZipImage, error) {
+func (e *EPUBImageProcessor) CoverTitleData(src image.Image, title string) (*epubzip.ZipImage, error) {
 	// Create a blur version of the cover
 	g := gift.New(epubimagefilters.CoverTitle(title))
-	dst := image.NewGray(g.Bounds(img.Bounds()))
+	dst := e.createImage(src, g.Bounds(src.Bounds()))
-	g.Draw(dst, img)
+	g.Draw(dst, src)
 
 	return epubzip.CompressImage("OEBPS/Images/title.jpg", dst, e.Image.Quality)
 }

internal/epub/options/epub_options.go

@@ -10,8 +10,13 @@ type Crop struct {
 	Left, Up, Right, Bottom int
 }
 
+type Color struct {
+	Foreground, Background string
+}
+
 type View struct {
 	Width, Height int
+	Color         Color
 }
 
 type Image struct {
@@ -25,6 +30,7 @@ type Image struct {
 	Manga               bool
 	HasCover            bool
 	View                *View
+	GrayScale           bool
 }
 
 type Options struct {

internal/epub/templates/epub_templates_content.go

@@ -195,9 +195,11 @@ func getSpine(o *ContentOptions) []tag {
 				"",
 			})
 		}
+		// register position for style adjustment
+		img.Position = getSpread(img.DoublePage)
 		spine = append(spine, tag{
 			"itemref",
-			tagAttrs{"idref": img.PageKey(), "properties": getSpread(img.DoublePage)},
+			tagAttrs{"idref": img.PageKey(), "properties": img.Position},
 			"",
 		})
 	}

internal/epub/templates/epub_templates_style.css.tmpl

@@ -1,12 +1,12 @@
 body {
-    color: #000;
+    color: #{{ .View.Color.Foreground }};
-    background: #FFF;
+    background: #{{ .View.Color.Background }};
     top: 0;
     left: 0;
     margin: 0;
     padding: 0;
-    width: {{ .PageWidth }}px;
+    width: {{ .View.Width }}px;
-    height: {{ .PageHeight }}px;
+    height: {{ .View.Height }}px;
     text-align: center;
 }
 

main.go

@@ -114,6 +114,8 @@ $ go install github.com/celogeek/go-comic-converter/v%d@%s
 		DryVerbose:                 cmd.Options.DryVerbose,
 		Quiet:                      cmd.Options.Quiet,
 		Image: &epuboptions.Image{
+			Quality:   cmd.Options.Quality,
+			GrayScale: cmd.Options.Grayscale,
 			Crop: &epuboptions.Crop{
 				Enabled: cmd.Options.Crop,
 				Left:    cmd.Options.CropRatioLeft,
@@ -121,7 +123,6 @@ $ go install github.com/celogeek/go-comic-converter/v%d@%s
 				Right:   cmd.Options.CropRatioRight,
 				Bottom:  cmd.Options.CropRatioBottom,
 			},
-			Quality:             cmd.Options.Quality,
 			Brightness:          cmd.Options.Brightness,
 			Contrast:            cmd.Options.Contrast,
 			AutoRotate:          cmd.Options.AutoRotate,
@@ -132,6 +133,10 @@ $ go install github.com/celogeek/go-comic-converter/v%d@%s
 			View: &epuboptions.View{
 				Width:  perfectWidth,
 				Height: perfectHeight,
+				Color: epuboptions.Color{
+					Foreground: cmd.Options.ForegroundColor,
+					Background: cmd.Options.BackgroundColor,
+				},
 			},
 		},
 	}).Write(); err != nil {