public static OutputStream decodeBitmap(String path) {
 
        BitmapFactory.Options opts = new BitmapFactory.Options();
        opts.inJustDecodeBounds = true;// 設定成了true,不佔用記憶體，只獲取bitmap寬高
        BitmapFactory.decodeFile(path, opts);
        opts.inSampleSize = computeSampleSize(opts, -1, 1024 * 800);
 
        opts.inJustDecodeBounds = false;// 這裡一定要將其設定回false，因為之前我們將其設定成了true
        opts.inPurgeable = true;
        opts.inInputShareable = true;
        opts.inDither = false;
        opts.inPurgeable = true;
        opts.inTempStorage = new byte[16 * 1024];
        FileInputStream is = null;
        Bitmap bmp = null;
        InputStream ins = null;
        ByteArrayOutputStream baos = null;
        try {
            is = new FileInputStream(path);
            bmp = BitmapFactory.decodeFileDescriptor(is.getFD(), null, opts);           
            double scale = getScaling(opts.outWidth * opts.outHeight, 1024 * 600);
            Bitmap bmp2 = Bitmap.createScaledBitmap(bmp,
                    (int) (opts.outWidth * scale),
                    (int) (opts.outHeight * scale), true);
            bmp.recycle();
            baos = new ByteArrayOutputStream();
            bmp2.compress(Bitmap.CompressFormat.JPEG, 100, baos);
            bmp2.recycle();
            return baos;
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                is.close();
                ins.close();
                baos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            System.gc();
        }
        return baos;
    }
 
private static double getScaling(int src, int des) {
/**
 * 目標尺寸÷原尺寸 sqrt開方，得出寬高百分比
 */
    double scale = Math.sqrt((double) des / (double) src);
    return scale;
}