Golang opj_read_header示例

示例#1

文件： jp2_image.go 项目： uoregon-libraries/newspaper-jp2-viewer

func (i *JP2Image) ReadHeader() error {
	if i.image != nil {
		return nil
	}

	if err := i.initializeCodec(); err != nil {
		return err
	}

	if err := i.initializeStream(); err != nil {
		return err
	}

	if C.opj_read_header(i.stream, i.codec, &i.image) == C.OPJ_FALSE {
		return errors.New("failed to read the header")
	}

	return nil
}

示例#2

文件： openjpeg.go 项目： eikeon/brikker

func NewImageTile(filename string, r image.Rectangle, width, height int) (err error, tile *ImageTile) {
	l_stream := C.opj_stream_create_default_file_stream_v3(C.CString(filename), 1)
	if l_stream == nil {
		return errors.New("failed to create stream"), nil
	}

	l_codec := C.opj_create_decompress(C.OPJ_CODEC_JP2)

	var parameters C.opj_dparameters_t
	C.opj_set_default_decoder_parameters(&parameters)
	level := desired_progression_level(r, width, height)
	log.Println("desired level:", level)
	//(parameters).cp_reduce = C.OPJ_UINT32(level)

	C.set_handlers(l_codec)

	if err == nil && C.opj_setup_decoder(l_codec, &parameters) == C.OPJ_FALSE {
		err = errors.New("failed to setup decoder")
	}

	if err == nil && C.opj_set_decoded_resolution_factor(l_codec, C.OPJ_UINT32(level)) == C.OPJ_FALSE {
		err = errors.New("failed to set decode resolution factor")
	}

	var img *C.opj_image_t
	if err == nil && C.opj_read_header(l_stream, l_codec, &img) == C.OPJ_FALSE {
		err = errors.New("failed to read the header")
	}

	if err == nil {
		log.Println("num comps:", img.numcomps)
		log.Println("x0:", img.x0, "x1:", img.x1, "y0:", img.y0, "y1:", img.y1)
	}

	if err == nil && C.opj_set_decode_area(l_codec, img, C.OPJ_INT32(r.Min.X), C.OPJ_INT32(r.Min.Y), C.OPJ_INT32(r.Max.X), C.OPJ_INT32(r.Max.Y)) == C.OPJ_FALSE {
		err = errors.New("failed to set the decoded area")
	}

	if err == nil && C.opj_decode(l_codec, l_stream, img) == C.OPJ_FALSE {
		err = errors.New("failed to decode image")
	}
	if err == nil && C.opj_end_decompress(l_codec, l_stream) == C.OPJ_FALSE {
		err = errors.New("failed to decode image")
	}

	C.opj_stream_destroy_v3(l_stream)
	if l_codec != nil {
		C.opj_destroy_codec(l_codec)
	}

	if err == nil {
		var comps []C.opj_image_comp_t
		compsSlice := (*reflect.SliceHeader)((unsafe.Pointer(&comps)))
		compsSlice.Cap = int(img.numcomps)
		compsSlice.Len = int(img.numcomps)
		compsSlice.Data = uintptr(unsafe.Pointer(img.comps))

		bounds := image.Rect(0, 0, int(comps[0].w), int(comps[0].h))

		var data []int32
		dataSlice := (*reflect.SliceHeader)((unsafe.Pointer(&data)))
		dataSlice.Cap = bounds.Dx() * bounds.Dy()
		dataSlice.Len = bounds.Dx() * bounds.Dy()
		dataSlice.Data = uintptr(unsafe.Pointer(comps[0].data))

		tile = &ImageTile{data, bounds, bounds.Dx(), img}
		runtime.SetFinalizer(tile, func(it *ImageTile) {
			C.opj_image_destroy(it.img)
		})
	} else {
		C.opj_image_destroy(img)
	}
	return
}