add option to choose aspect ratio

internal/converter/converter.go

@@ -84,6 +84,12 @@ func (c *Converter) AddIntParam(p *int, name string, value int, usage string) {
 	c.order = append(c.order, converterOrderName{value: name})
 }
 
+// Add an float parameter
+func (c *Converter) AddFloatParam(p *float64, name string, value float64, usage string) {
+	c.Cmd.Float64Var(p, name, value, usage)
+	c.order = append(c.order, converterOrderName{value: name})
+}
+
 // Add a boolean parameter
 func (c *Converter) AddBoolParam(p *bool, name string, value bool, usage string) {
 	c.Cmd.BoolVar(p, name, value, usage)
@@ -121,6 +127,7 @@ func (c *Converter) InitParse() {
 	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.AddBoolParam(&c.Options.NoResize, "noresize", c.Options.NoResize, "Do not reduce image size if exceed device size")
 	c.AddStringParam(&c.Options.Format, "format", c.Options.Format, "Format of output images: jpeg (lossy), png (lossless)")
+	c.AddFloatParam(&c.Options.AspectRatio, "aspect-ratio", c.Options.AspectRatio, "Aspect ratio (height/width) of the output\n -1 = same as device\n  0 = same as source\n1.6 = amazon advice for kindle")
 
 	c.AddSection("Default config")
 	c.AddBoolParam(&c.Options.Show, "show", false, "Show your default parameters")
@@ -351,6 +358,11 @@ func (c *Converter) Validate() error {
 		return errors.New("format should be jpeg or png")
 	}
 
+	// Aspect Ratio
+	if c.Options.AspectRatio < 0 && c.Options.AspectRatio != -1 {
+		return errors.New("aspect ratio should be: -1, 0, > 0")
+	}
+
 	return nil
 }
 

internal/converter/options/converter_options.go

@@ -43,6 +43,7 @@ type Options struct {
 	BackgroundColor            string  `yaml:"background_color"`
 	NoResize                   bool    `yaml:"noresize"`
 	Format                     string  `yaml:"format"`
+	AspectRatio                float64 `yaml:"aspect_ratio"`
 
 	// Default Config
 	Show  bool `yaml:"-"`
@@ -94,6 +95,7 @@ func New() *Options {
 		BackgroundColor:            "FFF",
 		NoResize:                   false,
 		Format:                     "jpeg",
+		AspectRatio:                0,
 		profiles:                   profiles.New(),
 	}
 }
@@ -167,6 +169,13 @@ func (o *Options) ShowConfig() string {
 		sortpathmode = "path=alphanum, file=alphanum"
 	}
 
+	aspectRatio := "auto"
+	if o.AspectRatio > 0 {
+		aspectRatio = fmt.Sprintf("1:%.02f", o.AspectRatio)
+	} else if o.AspectRatio < 0 {
+		aspectRatio = fmt.Sprintf("1:%0.2f (device)", float64(profile.Height)/float64(profile.Width))
+	}
+
 	var b strings.Builder
 	for _, v := range []struct {
 		Key       string
@@ -192,6 +201,7 @@ func (o *Options) ShowConfig() string {
 		{"Foreground Color", fmt.Sprintf("#%s", o.ForegroundColor), true},
 		{"Background Color", fmt.Sprintf("#%s", o.BackgroundColor), true},
 		{"Resize", !o.NoResize, true},
+		{"Aspect Ratio", aspectRatio, true},
 	} {
 		if v.Condition {
 			b.WriteString(fmt.Sprintf("\n    %-26s: %v", v.Key, v.Value))

internal/epub/epub.go

@@ -194,8 +194,7 @@ func (e *ePub) getTree(images []*epubimage.Image, skip_files bool) string {
 	return c.WriteString("")
 }
 
-func (e *ePub) ComputeViewPort(epubParts []*epubPart) {
+func (e *ePub) computeAspectRatio(epubParts []*epubPart) float64 {
-	// readjusting view port
 	var (
 		bestAspectRatio      float64
 		bestAspectRatioCount int
@@ -209,7 +208,7 @@ func (e *ePub) ComputeViewPort(epubParts []*epubPart) {
 	for _, p := range epubParts {
 		aspectRatio[trunc(p.Cover.OriginalAspectRatio)]++
 		for _, i := range p.Images {
-			aspectRatio[trunc(i.OriginalAspectRatio)/100]++
+			aspectRatio[trunc(i.OriginalAspectRatio)]++
 		}
 	}
 
@@ -219,6 +218,20 @@ func (e *ePub) ComputeViewPort(epubParts []*epubPart) {
 		}
 	}
 
+	return bestAspectRatio
+}
+
+func (e *ePub) computeViewPort(epubParts []*epubPart) {
+	if e.Image.View.AspectRatio == -1 {
+		return //keep device size
+	}
+
+	// readjusting view port
+	bestAspectRatio := e.Image.View.AspectRatio
+	if bestAspectRatio == 0 {
+		bestAspectRatio = e.computeAspectRatio(epubParts)
+	}
+
 	viewWidth, viewHeight := int(float64(e.Image.View.Height)/bestAspectRatio), int(float64(e.Image.View.Width)*bestAspectRatio)
 	if viewWidth > e.Image.View.Width {
 		e.Image.View.Height = viewHeight
@@ -265,7 +278,7 @@ func (e *ePub) Write() error {
 		Quiet:       e.Quiet,
 	})
 
-	e.ComputeViewPort(epubParts)
+	e.computeViewPort(epubParts)
 	for i, part := range epubParts {
 		ext := filepath.Ext(e.Output)
 		suffix := ""

internal/epub/options/epub_options.go

@@ -16,6 +16,7 @@ type Color struct {
 
 type View struct {
 	Width, Height int
+	AspectRatio   float64
 	Color         Color
 }
 

main.go

@@ -132,6 +132,7 @@ $ go install github.com/celogeek/go-comic-converter/v%d@%s
 			View: &epuboptions.View{
 				Width:       profile.Width,
 				Height:      profile.Height,
+				AspectRatio: cmd.Options.AspectRatio,
 				Color: epuboptions.Color{
 					Foreground: cmd.Options.ForegroundColor,
 					Background: cmd.Options.BackgroundColor,