// 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.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
}
// WriteJPEG writes a YUVImage as a JPEG into dest.
func WriteJPEG(img *YUVImage, dest io.Writer, params CompressionParameters) (err error) {
defer func() {
if r := recover(); r != nil {
img = nil
var ok bool
err, ok = r.(error)
if !ok {
err = fmt.Errorf("JPEG error: %v", r)
}
}
}()
cinfo := (*C.struct_jpeg_compress_struct)(C.malloc(C.size_t(unsafe.Sizeof(C.struct_jpeg_compress_struct{}))))
if cinfo == nil {
panic("Failed to allocate cinfo")
}
defer C.free(unsafe.Pointer(cinfo))
cinfo.err = (*C.struct_jpeg_error_mgr)(C.malloc(C.size_t(unsafe.Sizeof(C.struct_jpeg_error_mgr{}))))
if cinfo.err == nil {
panic("Failed to allocate cinfo.err")
}
defer C.free(unsafe.Pointer(cinfo.err))
// No subsampling suport for now
if img.Format != YUV444 && img.Format != Grayscale {
panic("Unsupported colorspace")
}
// Setup error handling
C.jpeg_std_error(cinfo.err)
cinfo.err.error_exit = (*[0]byte)(C.error_panic)
// Initialize compression object
C.c_jpeg_create_compress(cinfo)
defer C.jpeg_destroy_compress(cinfo)
destManager := makeDestinationManager(dest, cinfo)
defer C.free(unsafe.Pointer(destManager))
// Set up compression parameters
cinfo.image_width = C.JDIMENSION(img.Width)
cinfo.image_height = C.JDIMENSION(img.Height)
cinfo.input_components = 3
cinfo.in_color_space = C.JCS_YCbCr
if img.Format == Grayscale {
cinfo.input_components = 1
cinfo.in_color_space = C.JCS_GRAYSCALE
}
C.jpeg_set_defaults(cinfo)
C.jpeg_set_quality(cinfo, C.int(params.Quality), C.TRUE)
if params.Optimize {
cinfo.optimize_coding = C.TRUE
} else {
cinfo.optimize_coding = C.FALSE
}
C.jpeg_set_colorspace(cinfo, cinfo.in_color_space)
if params.FastDCT {
cinfo.dct_method = C.JDCT_IFAST
} else {
cinfo.dct_method = C.JDCT_ISLOW
}
compInfo := (*[3]C.jpeg_component_info)(unsafe.Pointer(cinfo.comp_info))
for i := 0; i < int(cinfo.input_components); i++ {
compInfo[i].h_samp_factor = 1
compInfo[i].v_samp_factor = 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 yuvPtrInt [3][AlignSize]C.JSAMPROW
yuvPtr := [3]C.JSAMPARRAY{
C.JSAMPARRAY(unsafe.Pointer(&yuvPtrInt[0][0])),
C.JSAMPARRAY(unsafe.Pointer(&yuvPtrInt[1][0])),
C.JSAMPARRAY(unsafe.Pointer(&yuvPtrInt[2][0])),
}
// Encode the image.
var row C.JDIMENSION
for row = 0; row < cinfo.image_height; {
// First fill in the pointers into the plane data buffers
for i := 0; i < int(cinfo.num_components); i++ {
for j := 0; j < int(C.DCTSIZE*compInfo[i].v_samp_factor); j++ {
compRow := (int(row) + j)
yuvPtrInt[i][j] = C.JSAMPROW(unsafe.Pointer(&img.Data[i][img.Stride[i]*compRow]))
}
}
// Get the data
row += C.jpeg_write_raw_data(cinfo, C.JSAMPIMAGE(unsafe.Pointer(&yuvPtr[0])), C.JDIMENSION(C.DCTSIZE*compInfo[0].v_samp_factor))
}
// Clean up
C.jpeg_finish_compress(cinfo)
return
}