func crop(filename string) {
f, err := os.Open("testdata/" + filename + ".gif")
if err != nil {
log.Fatal(err.Error())
}
defer f.Close()
im, err := gif.DecodeAll(f)
if err != nil {
log.Fatal(err.Error())
}
firstFrame := im.Image[0]
imgBounds := firstFrame.Bounds()
img := image.NewRGBA(imgBounds)
for index, frame := range im.Image {
bounds := frame.Bounds()
draw.Draw(img, bounds, frame, bounds.Min, draw.Src)
im.Image[index] = ImageToPaletted(img.SubImage(image.Rect(
imgBounds.Min.X,
imgBounds.Min.Y+imgBounds.Dy()/4,
imgBounds.Max.X,
imgBounds.Max.Y-imgBounds.Dy()/4)))
}
out, err := os.Create(filename + ".out.gif")
if err != nil {
log.Fatal(err.Error())
}
defer out.Close()
gogif.EncodeAll(out, im)
}
func process(filename string) {
f, err := os.Open("testdata/" + filename + ".gif")
if err != nil {
log.Fatal(err.Error())
}
defer f.Close()
im, err := gif.DecodeAll(f)
if err != nil {
log.Fatal(err.Error())
}
firstFrame := im.Image[0]
img := image.NewRGBA(firstFrame.Bounds())
// Frames in an animated gif aren't necessarily the same size. Subsequent
// frames are overlayed on previous frames. Resizing the frames individually
// causes problems due to aliasing of transparent pixels. In theory we can get
// around this by building up the resultant frames from all previous frames.
// This results in slower processing times and a bigger end image, but so far
// I haven't thought of an alternative method.
for index, frame := range im.Image {
bounds := frame.Bounds()
draw.Draw(img, bounds, frame, bounds.Min, draw.Src)
im.Image[index] = ImageToPaletted(ProcessImage(img))
}
out, err := os.Create(filename + ".out.gif")
if err != nil {
log.Fatal(err.Error())
}
defer out.Close()
gogif.EncodeAll(out, im)
}