public class BitmapUtil {
    /**
     *
     * @param bitmap
     * @param maxSize 當傳入的bitmap的大小大於maxSize時，壓縮圖片至maxSize
     * @return
     */
    public static Bitmap getCompressedBitmap(Bitmap bitmap,double maxSize) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.JPEG, 100
 
, baos);
        byte[] b = baos.toByteArray();
        //將位元組換成KB
        double mid = b.length / 1024;
        if (mid > maxSize) {
            double i = mid / maxSize;
            return compressBitmap(bitmap, bitmap.getWidth() / Math.sqrt(i),
                    bitmap.getHeight() / Math.sqrt(i));
        }
        return
 
 bitmap;
    }

    private static Bitmap compressBitmap(Bitmap bitmap, double newWidth, double newHeight) {
        float width = bitmap.getWidth();
        float height = bitmap.getHeight();
        Matrix matrix = new Matrix();
        float scaleWidth = ((float) newWidth) / width;
        float scaleHeight = ((float
 
) newHeight) / height;
        matrix.postScale(scaleWidth, scaleHeight);
        return Bitmap.createBitmap(bitmap, 0, 0, (int) width, (int) height, matrix, true);
    }

}