do not enlarge smaller images

all width/height are computed based on viewport dimension.
images will enlarge if smaller, and resize to fit if larger.

internal/epub/image/epub_image.go

@@ -6,6 +6,7 @@ package epubimage
 import (
 	"fmt"
 	"image"
+	"strings"
 )
 
 type Image struct {
@@ -72,24 +73,48 @@ 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, align string) string {
-	marginW, marginH := float64(viewWidth-i.Width)/2, float64(viewHeight-i.Height)/2
+	relWidth, relHeight := i.RelSize(viewWidth, viewHeight)
+	marginW, marginH := float64(viewWidth-relWidth)/2, float64(viewHeight-relHeight)/2
 
+	style := []string{}
+
+	style = append(style, fmt.Sprintf("width:%dpx", relWidth))
+	style = append(style, fmt.Sprintf("height:%dpx", relHeight))
+	style = append(style, fmt.Sprintf("top:%.2f%%", marginH*100/float64(viewHeight)))
 	if align == "" {
 		switch i.Position {
 		case "rendition:page-spread-left":
-			align = "right:0"
+			style = append(style, "right:0")
 		case "rendition:page-spread-right":
-			align = "left:0"
+			style = append(style, "left:0")
 		default:
-			align = fmt.Sprintf("left:%.2f%%", marginW*100/float64(viewWidth))
+			style = append(style, fmt.Sprintf("left:%.2f%%", marginW*100/float64(viewWidth)))
 		}
+	} else {
+		style = append(style, align)
 	}
 
-	return fmt.Sprintf(
-		"width:%dpx; height:%dpx; top:%.2f%%; %s;",
-		i.Width,
-		i.Height,
-		marginH*100/float64(viewHeight),
-		align,
-	)
+	return strings.Join(style, "; ")
+}
+
+func (i *Image) RelSize(viewWidth, viewHeight int) (relWidth, relHeight int) {
+	w, h := viewWidth, viewHeight
+	srcw, srch := i.Width, i.Height
+
+	if w <= 0 || h <= 0 || srcw <= 0 || srch <= 0 {
+		return
+	}
+
+	wratio := float64(srcw) / float64(w)
+	hratio := float64(srch) / float64(h)
+
+	if wratio > hratio {
+		relWidth = w
+		relHeight = int(float64(srch)/wratio + 0.5)
+	} else {
+		relHeight = h
+		relWidth = int(float64(srcw)/hratio + 0.5)
+	}
+
+	return
 }

internal/epub/imagefilters/epub_image_filters_resize.go

@@ -1,48 +0,0 @@
-package epubimagefilters
-
-import (
-	"image"
-	"image/draw"
-
-	"github.com/disintegration/gift"
-)
-
-// Resize image by keeping aspect ratio.
-// This will reduce or enlarge image to fit into the viewWidth and viewHeight.
-func Resize(viewWidth, viewHeight int, resampling gift.Resampling) gift.Filter {
-	return &resizeFilter{
-		viewWidth, viewHeight, resampling,
-	}
-}
-
-type resizeFilter struct {
-	viewWidth, viewHeight int
-	resampling            gift.Resampling
-}
-
-func (p *resizeFilter) Bounds(srcBounds image.Rectangle) image.Rectangle {
-	w, h := p.viewWidth, p.viewHeight
-	srcw, srch := srcBounds.Dx(), srcBounds.Dy()
-
-	if w <= 0 || h <= 0 || srcw <= 0 || srch <= 0 {
-		return image.Rect(0, 0, 0, 0)
-	}
-
-	wratio := float64(srcw) / float64(w)
-	hratio := float64(srch) / float64(h)
-
-	var dstw, dsth int
-	if wratio > hratio {
-		dstw = w
-		dsth = int(float64(srch)/wratio + 0.5)
-	} else {
-		dsth = h
-		dstw = int(float64(srcw)/hratio + 0.5)
-	}
-
-	return image.Rect(0, 0, dstw, dsth)
-}
-
-func (p *resizeFilter) Draw(dst draw.Image, src image.Image, options *gift.Options) {
-	gift.Resize(dst.Bounds().Dx(), dst.Bounds().Dy(), p.resampling).Draw(dst, src, options)
-}

internal/epub/imageprocessor/epub_image_processor.go

@@ -202,7 +202,7 @@ func (e *EPUBImageProcessor) transformImage(src image.Image, srcId int) []image.
 	}
 
 	filters = append(filters,
-		epubimagefilters.Resize(e.Image.View.Width, e.Image.View.Height, gift.LanczosResampling),
+		gift.ResizeToFit(e.Image.View.Width, e.Image.View.Height, gift.LanczosResampling),
 		epubimagefilters.Pixel(),
 	)
 
@@ -234,7 +234,7 @@ func (e *EPUBImageProcessor) transformImage(src image.Image, srcId int) []image.
 		g := gift.New(splitFilter...)
 		g.Add(
 			epubimagefilters.CropSplitDoublePage(b),
-			epubimagefilters.Resize(e.Image.View.Width, e.Image.View.Height, gift.LanczosResampling),
+			gift.ResizeToFit(e.Image.View.Width, e.Image.View.Height, gift.LanczosResampling),
 		)
 		dst := e.createImage(src, g.Bounds(src.Bounds()))
 		g.Draw(dst, src)

internal/epub/templates/epub_templates_text.xhtml.tmpl

@@ -8,8 +8,6 @@
     <meta name="viewport" content="{{ .ViewPort }}"/>
   </head>
   <body>
-    <div>
-      <img src="../{{ .ImagePath }}" alt="{{ .Title }}" style="{{ .ImageStyle }}"/>
-    </div>
+    <img src="../{{ .ImagePath }}" alt="{{ .Title }}" style="{{ .ImageStyle }}"/>
   </body>
 </html>