func makeThumbnail(img image.Image, dimensions int) (thumbImg image.Image) {
// Calculate the largest square bounds for a thumbnail to preserve aspect ratio
b := img.Bounds()
srcBounds := b
dx, dy := b.Dx(), b.Dy()
if dx > dy {
offs := (dx - dy) / 2
srcBounds.Min.X += offs
srcBounds.Max.X -= offs
} else if dy > dx {
offs := (dy - dx) / 2
srcBounds.Min.Y += offs
srcBounds.Max.Y -= offs
} else {
// Already square.
}
//log.Printf("'%s': resize %v to %v\n", filename, b, srcBounds)
// Cut out the center square to a new image:
boximg := imaging.SubImageKind(img, srcBounds)
img = nil
// Apply resizing algorithm:
thumbImg = imaging.Resize(boximg, dimensions, dimensions, imaging.Lanczos)
boximg = nil
return
}
// Crops an image and outputs a new image file:
func cropImage(image_path string, left, top, right, bottom int) (tmp_output string, err error) {
cropBounds := image.Rect(left, top, right, bottom)
// Open the image for reading:
imf, err := os.Open(image_path)
if err != nil {
return "", err
}
defer imf.Close()
// Figure out what kind of image it is:
_, imageKind, err := image.DecodeConfig(imf)
if err != nil {
return "", err
}
imf.Seek(0, 0)
// Crop images:
switch imageKind {
case "gif":
// Decode all GIF frames and crop them:
// FIXME(jsd): This approach clearly does not work. An integrated decoder-encoder needs to be written
// for animated GIFs so as to preserve as much of the encoding details as possible and crop the
// transparent animation subframes over the full image.
var g *gif.GIF
g, err = gif.DecodeAll(imf)
if err != nil {
return "", err
}
// Crop all the frames:
for i, img := range g.Image {
if !cropBounds.In(img.Bounds()) {
return "", fmt.Errorf("Crop boundaries are not contained within image boundaries")
}
g.Image[i] = imaging.CloneKind(imaging.SubImageKind(img, cropBounds)).(*image.Paletted)
}
// Write the cropped images to a new GIF:
tmpf, err := TempFile(tmp_folder(), "crop-", ".gif")
if err != nil {
return "", err
}
defer tmpf.Close()
err = gif.EncodeAll(tmpf, g)
if err != nil {
return "", err
}
g.Image = nil
g.Delay = nil
g = nil
return tmpf.Name(), nil
case "jpeg":
img, err := jpeg.Decode(imf)
if err != nil {
return "", err
}
if !cropBounds.In(img.Bounds()) {
return "", fmt.Errorf("Crop boundaries are not contained within image boundaries")
}
tmpf, err := TempFile(tmp_folder(), "crop-", ".jpg")
if err != nil {
return "", err
}
defer tmpf.Close()
img = imaging.CloneKind(imaging.SubImageKind(img, cropBounds))
err = jpeg.Encode(tmpf, img, &jpeg.Options{Quality: 100})
if err != nil {
return "", err
}
return tmpf.Name(), nil
case "png":
img, err := png.Decode(imf)
if err != nil {
return "", err
}
if !cropBounds.In(img.Bounds()) {
return "", fmt.Errorf("Crop boundaries are not contained within image boundaries")
}
tmpf, err := TempFile(tmp_folder(), "crop-", ".png")
if err != nil {
return "", err
}
defer tmpf.Close()
img = imaging.SubImageKind(img, cropBounds)
err = png.Encode(tmpf, img)
if err != nil {
return "", err
}
return tmpf.Name(), nil
default:
return "", fmt.Errorf("Unrecognized image kind '%s'", imageKind)
}
}