opencv压缩效果更佳
Mat mat = Highgui.imread(mImgPath);
Mat detMat = new Mat();
Size size = new Size(mat.width()/2, mat.height()/2);
Imgproc.resize(mat, detMat, size);
List<Integer> list = new ArrayList<Integer>();
list.add(Highgui.CV_IMWRITE_JPEG_QUALITY);
list.add(quality);
if(Highgui.imwrite("/sdcard/compress_half.jpg", mat, list))