项目中有需求要对获取的图片进行压缩，并且是要压缩到固定大小，考虑到harmonyos中对图片质量压缩方式packing，压缩后要及时检查大小，就使用while循环一步步的压缩，直至压缩到目标值

let bitmap: ArrayBuffer;// 需要压缩的数据

let compressSize: number;// 目标大小

let considerBase64: boolean;// 是否考虑base64算法把字节数扩大4/3倍的影响
let result='';

if (bitmap){
        try {
                let imageSource = image.createImageSource(bitmap);
                let packer = image.createImagePacker();
                let packerData = await packer.packing(imageSource,{
                        format: 'image/jpeg'.
                        quality: 100
                }):
                if (considerBase64 && compresssize > 0){
                        compresssize = Math.ceil(compressSize * 3.0 / 4.0 -0.5);
                }
                let optionQuality = 90:
                while (compresssize > 0
                && packerData.byteLength / 1024 > compresssize
                && optionQuality > 0) {
                        let whilePacker = image.createImagePacker();
                        let whileImageSource = image.createImageSource(packerData);
                        packerData = await whilePacker.packing(whileImageSource,{
                                format: 'image/jpeg',
                                quality: optionQuality
                        });
                        optionQuality -= 10;

                }
                result = buffer.from(packerData).tostrinl('base64');
        } catch (error){
                hilog.error(0x0000, 'error: ' + JSOM.stringify(error), '%{public}s');
        }

}

----------------- end ---------------

后面会继续补充不足之处。