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
}