// encode image.YCbCr
func encodeYCbCr(cinfo *C.struct_jpeg_compress_struct, src *image.YCbCr, p *EncoderOptions) (err error) {
// Set up compression parameters
cinfo.image_width = C.JDIMENSION(src.Bounds().Dx())
cinfo.image_height = C.JDIMENSION(src.Bounds().Dy())
cinfo.input_components = 3
cinfo.in_color_space = C.JCS_YCbCr
C.jpeg_set_defaults(cinfo)
setupEncoderOptions(cinfo, p)
compInfo := (*[3]C.jpeg_component_info)(unsafe.Pointer(cinfo.comp_info))
colorVDiv := 1
switch src.SubsampleRatio {
case image.YCbCrSubsampleRatio444:
// 1x1,1x1,1x1
compInfo[Y].h_samp_factor, compInfo[Y].v_samp_factor = 1, 1
compInfo[Cb].h_samp_factor, compInfo[Cb].v_samp_factor = 1, 1
compInfo[Cr].h_samp_factor, compInfo[Cr].v_samp_factor = 1, 1
case image.YCbCrSubsampleRatio440:
// 1x2,1x1,1x1
compInfo[Y].h_samp_factor, compInfo[Y].v_samp_factor = 1, 2
compInfo[Cb].h_samp_factor, compInfo[Cb].v_samp_factor = 1, 1
compInfo[Cr].h_samp_factor, compInfo[Cr].v_samp_factor = 1, 1
colorVDiv = 2
case image.YCbCrSubsampleRatio422:
// 2x1,1x1,1x1
compInfo[Y].h_samp_factor, compInfo[Y].v_samp_factor = 2, 1
compInfo[Cb].h_samp_factor, compInfo[Cb].v_samp_factor = 1, 1
compInfo[Cr].h_samp_factor, compInfo[Cr].v_samp_factor = 1, 1
case image.YCbCrSubsampleRatio420:
// 2x2,1x1,1x1
compInfo[Y].h_samp_factor, compInfo[Y].v_samp_factor = 2, 2
compInfo[Cb].h_samp_factor, compInfo[Cb].v_samp_factor = 1, 1
compInfo[Cr].h_samp_factor, compInfo[Cr].v_samp_factor = 1, 1
colorVDiv = 2
}
// libjpeg raw data in is in planar format, which avoids unnecessary
// planar->packed->planar conversions.
cinfo.raw_data_in = C.TRUE
// Start compression
C.jpeg_start_compress(cinfo, C.TRUE)
C.encode_ycbcr(
cinfo,
C.JSAMPROW(unsafe.Pointer(&src.Y[0])),
C.JSAMPROW(unsafe.Pointer(&src.Cb[0])),
C.JSAMPROW(unsafe.Pointer(&src.Cr[0])),
C.int(src.YStride),
C.int(src.CStride),
C.int(colorVDiv),
)
C.jpeg_finish_compress(cinfo)
return
}
func Encode(w io.Writer, m image.Image, o *Options) error {
quality := 75
if o != nil {
quality = o.Quality
}
var cinfo C.struct_jpeg_compress_struct
var jerr C.struct_jpeg_error_mgr
var workBuf *C.uchar
var workBufLen C.ulong
cinfo.err = C.jpeg_std_error(&jerr)
C.jpeg_CreateCompress(&cinfo, C.JPEG_LIB_VERSION, C.size_t(unsafe.Sizeof(cinfo)))
C.jpeg_mem_dest(&cinfo, &workBuf, &workBufLen)
bounds := m.Bounds()
cinfo.image_width = C.JDIMENSION(bounds.Dx())
cinfo.image_height = C.JDIMENSION(bounds.Dy())
cinfo.input_components = 3
cinfo.in_color_space = C.JCS_RGB
C.jpeg_set_defaults(&cinfo)
C.jpeg_set_quality(&cinfo, C.int(quality), C.boolean(1))
C.jpeg_start_compress(&cinfo, C.boolean(1))
rowBuf := make([]byte, cinfo.image_width*3)
for cinfo.next_scanline < cinfo.image_height {
for x := 0; x < int(cinfo.image_width); x += 1 {
r, g, b, _ := m.At(x, int(cinfo.next_scanline)).RGBA()
rowBuf[x*3] = byte(r >> 8)
rowBuf[x*3+1] = byte(g >> 8)
rowBuf[x*3+2] = byte(b >> 8)
}
rowPointer := C.JSAMPROW(unsafe.Pointer(&rowBuf[0]))
C.jpeg_write_scanlines(&cinfo, &rowPointer, 1)
}
C.jpeg_finish_compress(&cinfo)
C.jpeg_destroy_compress(&cinfo)
outBs := C.GoBytes(unsafe.Pointer(workBuf), C.int(workBufLen))
w.Write(outBs)
C.free(unsafe.Pointer(workBuf))
return nil
}
// encode image.Gray
func encodeGray(cinfo *C.struct_jpeg_compress_struct, src *image.Gray, p *EncoderOptions) (err error) {
// Set up compression parameters
cinfo.image_width = C.JDIMENSION(src.Bounds().Dx())
cinfo.image_height = C.JDIMENSION(src.Bounds().Dy())
cinfo.input_components = 1
cinfo.in_color_space = C.JCS_GRAYSCALE
C.jpeg_set_defaults(cinfo)
setupEncoderOptions(cinfo, p)
compInfo := (*C.jpeg_component_info)(unsafe.Pointer(cinfo.comp_info))
compInfo.h_samp_factor, compInfo.v_samp_factor = 1, 1
// libjpeg raw data in is in planar format, which avoids unnecessary
// planar->packed->planar conversions.
cinfo.raw_data_in = C.TRUE
// Start compression
C.jpeg_start_compress(cinfo, C.TRUE)
// Allocate JSAMPIMAGE to hold pointers to one iMCU worth of image data
// this is a safe overestimate; we use the return value from
// jpeg_read_raw_data to figure out what is the actual iMCU row count.
var rowPtr [AlignSize]C.JSAMPROW
arrayPtr := [1]C.JSAMPARRAY{
C.JSAMPARRAY(unsafe.Pointer(&rowPtr[0])),
}
var rows C.JDIMENSION
for rows = 0; rows < cinfo.image_height; {
// First fill in the pointers into the plane data buffers
for j := 0; j < int(C.DCTSIZE*compInfo.v_samp_factor); j++ {
rowPtr[j] = C.JSAMPROW(unsafe.Pointer(&src.Pix[src.Stride*(int(rows)+j)]))
}
// Get the data
rows += C.jpeg_write_raw_data(cinfo, C.JSAMPIMAGE(unsafe.Pointer(&arrayPtr[0])), C.JDIMENSION(C.DCTSIZE*compInfo.v_samp_factor))
}
C.jpeg_finish_compress(cinfo)
return
}
// encode image.Gray
func encodeGray(cinfo *C.struct_jpeg_compress_struct, src *image.Gray, p *EncoderOptions) (err error) {
// Set up compression parameters
cinfo.image_width = C.JDIMENSION(src.Bounds().Dx())
cinfo.image_height = C.JDIMENSION(src.Bounds().Dy())
cinfo.input_components = 1
cinfo.in_color_space = C.JCS_GRAYSCALE
C.jpeg_set_defaults(cinfo)
setupEncoderOptions(cinfo, p)
compInfo := (*C.jpeg_component_info)(unsafe.Pointer(cinfo.comp_info))
compInfo.h_samp_factor, compInfo.v_samp_factor = 1, 1
// libjpeg raw data in is in planar format, which avoids unnecessary
// planar->packed->planar conversions.
cinfo.raw_data_in = C.TRUE
// Start compression
C.jpeg_start_compress(cinfo, C.TRUE)
C.encode_gray(cinfo, C.JSAMPROW(unsafe.Pointer(&src.Pix[0])), C.int(src.Stride))
C.jpeg_finish_compress(cinfo)
return
}
// encode image.YCbCr
func encodeYCbCr(cinfo *C.struct_jpeg_compress_struct, src *image.YCbCr, p *EncoderOptions) (err error) {
// Set up compression parameters
cinfo.image_width = C.JDIMENSION(src.Bounds().Dx())
cinfo.image_height = C.JDIMENSION(src.Bounds().Dy())
cinfo.input_components = 3
cinfo.in_color_space = C.JCS_YCbCr
C.jpeg_set_defaults(cinfo)
setupEncoderOptions(cinfo, p)
compInfo := (*[3]C.jpeg_component_info)(unsafe.Pointer(cinfo.comp_info))
colorVDiv := 1
switch src.SubsampleRatio {
case image.YCbCrSubsampleRatio444:
// 1x1,1x1,1x1
compInfo[Y].h_samp_factor, compInfo[Y].v_samp_factor = 1, 1
compInfo[Cb].h_samp_factor, compInfo[Cb].v_samp_factor = 1, 1
compInfo[Cr].h_samp_factor, compInfo[Cr].v_samp_factor = 1, 1
case image.YCbCrSubsampleRatio440:
// 1x2,1x1,1x1
compInfo[Y].h_samp_factor, compInfo[Y].v_samp_factor = 1, 2
compInfo[Cb].h_samp_factor, compInfo[Cb].v_samp_factor = 1, 1
compInfo[Cr].h_samp_factor, compInfo[Cr].v_samp_factor = 1, 1
colorVDiv = 2
case image.YCbCrSubsampleRatio422:
// 2x1,1x1,1x1
compInfo[Y].h_samp_factor, compInfo[Y].v_samp_factor = 2, 1
compInfo[Cb].h_samp_factor, compInfo[Cb].v_samp_factor = 1, 1
compInfo[Cr].h_samp_factor, compInfo[Cr].v_samp_factor = 1, 1
case image.YCbCrSubsampleRatio420:
// 2x2,1x1,1x1
compInfo[Y].h_samp_factor, compInfo[Y].v_samp_factor = 2, 2
compInfo[Cb].h_samp_factor, compInfo[Cb].v_samp_factor = 1, 1
compInfo[Cr].h_samp_factor, compInfo[Cr].v_samp_factor = 1, 1
colorVDiv = 2
}
// libjpeg raw data in is in planar format, which avoids unnecessary
// planar->packed->planar conversions.
cinfo.raw_data_in = C.TRUE
// Start compression
C.jpeg_start_compress(cinfo, C.TRUE)
// Allocate JSAMPIMAGE to hold pointers to one iMCU worth of image data
// this is a safe overestimate; we use the return value from
// jpeg_read_raw_data to figure out what is the actual iMCU row count.
var yRowPtr [AlignSize]C.JSAMPROW
var cbRowPtr [AlignSize]C.JSAMPROW
var crRowPtr [AlignSize]C.JSAMPROW
yCbCrPtr := [3]C.JSAMPARRAY{
C.JSAMPARRAY(unsafe.Pointer(&yRowPtr[0])),
C.JSAMPARRAY(unsafe.Pointer(&cbRowPtr[0])),
C.JSAMPARRAY(unsafe.Pointer(&crRowPtr[0])),
}
var rows C.JDIMENSION
for rows = 0; rows < cinfo.image_height; {
// First fill in the pointers into the plane data buffers
for j := 0; j < int(C.DCTSIZE*compInfo[Y].v_samp_factor); j++ {
yRowPtr[j] = C.JSAMPROW(unsafe.Pointer(&src.Y[src.YStride*(int(rows)+j)]))
}
for j := 0; j < int(C.DCTSIZE*compInfo[Cb].v_samp_factor); j++ {
cbRowPtr[j] = C.JSAMPROW(unsafe.Pointer(&src.Cb[src.CStride*(int(rows)/colorVDiv+j)]))
crRowPtr[j] = C.JSAMPROW(unsafe.Pointer(&src.Cr[src.CStride*(int(rows)/colorVDiv+j)]))
}
// Get the data
rows += C.jpeg_write_raw_data(cinfo, C.JSAMPIMAGE(unsafe.Pointer(&yCbCrPtr[0])), C.JDIMENSION(C.DCTSIZE*compInfo[0].v_samp_factor))
}
C.jpeg_finish_compress(cinfo)
return
}