func decodeCMYK(cinfo *C.struct_jpeg_decompress_struct) image.Image {
buf := make([]byte, int(cinfo.output_width*4))
scanLine := &buf[0]
scanLines := C.JSAMPARRAY(unsafe.Pointer(&scanLine))
img := image.NewRGBA(image.Rect(0, 0, int(cinfo.output_width), int(cinfo.output_height)))
for cinfo.output_scanline < cinfo.output_height {
y := int(cinfo.output_scanline)
C.jpeg_read_scanlines(cinfo, scanLines, 1)
for x := 0; x < int(cinfo.output_width); x += 1 {
off := y * img.Stride
c := buf[x*4+0]
m := buf[x*4+1]
y := buf[x*4+2]
k := buf[x*4+3]
r := uint8(255. * (1. - float64(c)) * (1. - float64(k)))
g := uint8(255. * (1. - float64(m)) * (1. - float64(k)))
b := uint8(255. * (1. - float64(y)) * (1. - float64(k)))
img.Pix[off+4*x+0] = r
img.Pix[off+4*x+1] = g
img.Pix[off+4*x+2] = b
img.Pix[off+4*x+3] = 255
}
}
return img
}
func decodeGrayscale(cinfo *C.struct_jpeg_decompress_struct) image.Image {
buf := make([]byte, int(cinfo.output_width))
scanLine := &buf[0]
scanLines := C.JSAMPARRAY(unsafe.Pointer(&scanLine))
img := image.NewGray(image.Rect(0, 0, int(cinfo.output_width), int(cinfo.output_height)))
for cinfo.output_scanline < cinfo.output_height {
y := int(cinfo.output_scanline)
C.jpeg_read_scanlines(cinfo, scanLines, 1)
for x := 0; x < int(cinfo.output_width); x += 1 {
off := y * img.Stride
img.Pix[off+x] = buf[x]
}
}
return img
}
func decodeRGB(cinfo *C.struct_jpeg_decompress_struct) image.Image {
buf := make([]byte, int(cinfo.output_width*3))
scanLine := &buf[0]
scanLines := C.JSAMPARRAY(unsafe.Pointer(&scanLine))
img := image.NewRGBA(image.Rect(0, 0, int(cinfo.output_width), int(cinfo.output_height)))
for cinfo.output_scanline < cinfo.output_height {
y := int(cinfo.output_scanline)
C.jpeg_read_scanlines(cinfo, scanLines, 1)
for x := 0; x < int(cinfo.output_width); x += 1 {
off := y * img.Stride
img.Pix[off+4*x+0] = buf[x*3+0]
img.Pix[off+4*x+1] = buf[x*3+1]
img.Pix[off+4*x+2] = buf[x*3+2]
img.Pix[off+4*x+3] = 255
}
}
return img
}
