// DecodeConfig returns the color model and dimensions of a JPEG image without decoding the entire image.
func DecodeConfig(r io.Reader) (config image.Config, err error) {
// Recover panic
defer func() {
if r := recover(); r != nil {
var ok bool
err, ok = r.(error)
if !ok {
err = fmt.Errorf("JPEG error: %v", r)
}
}
}()
dinfo := C.new_decompress()
defer C.destroy_decompress(dinfo)
srcManager := makeSourceManager(r, dinfo)
defer releaseSourceManager(srcManager)
C.jpeg_read_header(dinfo, C.TRUE)
config = image.Config{
ColorModel: color.YCbCrModel,
Width: int(dinfo.image_width),
Height: int(dinfo.image_height),
}
return
}
// DecodeIntoRGB reads a JPEG data stream from r and returns decoded image as an rgb.Image with RGB colors.
func DecodeIntoRGB(r io.Reader, options *DecoderOptions) (dest *rgb.Image, err error) {
// Recover panic
defer func() {
if r := recover(); r != nil {
log.Println(r)
if _, ok := r.(error); !ok {
err = fmt.Errorf("JPEG error: %v", r)
}
}
}()
dinfo := C.new_decompress()
defer C.destroy_decompress(dinfo)
srcManager := makeSourceManager(r, dinfo)
defer releaseSourceManager(srcManager)
C.jpeg_read_header(dinfo, C.TRUE)
setupDecoderOptions(dinfo, options)
C.jpeg_calc_output_dimensions(dinfo)
dest = rgb.NewImage(image.Rect(0, 0, int(dinfo.output_width), int(dinfo.output_height)))
dinfo.out_color_space = C.JCS_RGB
readScanLines(dinfo, dest.Pix, dest.Stride)
return
}
// DecodeIntoRGBA reads a JPEG data stream from r and returns decoded image as an image.RGBA with RGBA colors.
// This function only works with libjpeg-trubo, not libjpeg.
func DecodeIntoRGBA(r io.Reader, options *DecoderOptions) (dest *image.RGBA, err error) {
// Recover panic
defer func() {
if r := recover(); r != nil {
log.Println(r)
if _, ok := r.(error); !ok {
err = fmt.Errorf("JPEG error: %v", r)
}
}
}()
dinfo := C.new_decompress()
defer C.destroy_decompress(dinfo)
srcManager := makeSourceManager(r, dinfo)
defer releaseSourceManager(srcManager)
C.jpeg_read_header(dinfo, C.TRUE)
setupDecoderOptions(dinfo, options)
C.jpeg_calc_output_dimensions(dinfo)
dest = image.NewRGBA(image.Rect(0, 0, int(dinfo.output_width), int(dinfo.output_height)))
colorSpace := C.getJCS_EXT_RGBA()
if colorSpace == C.JCS_UNKNOWN {
return nil, errors.New("JCS_EXT_RGBA is not supported (probably built without libjpeg-trubo)")
}
dinfo.out_color_space = colorSpace
readScanLines(dinfo, dest.Pix, dest.Stride)
return
}
// Decode reads a JPEG data stream from r and returns decoded image as an image.Image.
// Output image has YCbCr colors or 8bit Grayscale.
func Decode(r io.Reader, options *DecoderOptions) (dest image.Image, err error) {
// Recover panic
defer func() {
if r := recover(); r != nil {
log.Println(r)
if _, ok := r.(error); !ok {
err = fmt.Errorf("JPEG error: %v", r)
}
}
}()
dinfo := C.new_decompress()
defer C.destroy_decompress(dinfo)
srcManager := makeSourceManager(r, dinfo)
defer releaseSourceManager(srcManager)
C.jpeg_read_header(dinfo, C.TRUE)
setupDecoderOptions(dinfo, options)
switch dinfo.num_components {
case 1:
if dinfo.jpeg_color_space != C.JCS_GRAYSCALE {
return nil, errors.New("Image has unsupported colorspace")
}
dest, err = decodeGray(dinfo)
case 3:
switch dinfo.jpeg_color_space {
case C.JCS_YCbCr:
dest, err = decodeYCbCr(dinfo)
case C.JCS_RGB:
dest, err = decodeRGB(dinfo)
default:
return nil, errors.New("Image has unsupported colorspace")
}
}
return
}