压缩图片

一个人的端午太过无聊了，记一下最近遇到的一个bug。话说在用WebView加载一张本地图片的时候，直接加载速度比较慢，于是我打算将图片压缩一下质量再转为输入流给WebView，结果耗时更长了，代码如下：

long time = System.currentTimeMillis();                Log.e(TAG, "shouldInterceptRequest: ");                Bitmap bmp = BitmapFactory.decodeFile(imgPath);                ByteArrayOutputStream baos = new ByteArrayOutputStream();                bmp.compress(Bitmap.CompressFormat.PNG,80,baos);                Log.e(TAG, "shouldInterceptRequest: "+(System.currentTimeMillis()-time));

05-29 16:54:33.590 4769-4832/com.wxxiaomi.ming.webviewcachemodule E/StreamActivity: shouldInterceptRequest: 05-29 16:55:43.740 4769-4832/com.wxxiaomi.ming.webviewcachemodule E/StreamActivity: shouldInterceptRequest: 70151

后来我一直不明白，为什么我压缩的结果是如此慢？直到看了人家的压缩以后才发现，我加载同样一张不到6M图片的图片，耗时60秒——70秒，而压缩以后耗时只有10%，并且，APP使使用的内存差别也很大，我的压缩达结果占用内存达到100M以上，而别人压缩以后加载内存占用不到30M，那么别人是怎么压缩的呢？

 Bitmap bitmap = compressBitmap(srcPath, rqsW, rqsH);                        long time = System.currentTimeMillis();                        Log.e("StreamActivity", "shouldInterceptRequest: ");//                        Bitmap bitmap = BitmapFactory.decodeFile(srcPath);                        int degree = getDegress(srcPath);                        try {                            if (degree != 0) bitmap = rotateBitmap(bitmap, degree);                            ByteArrayOutputStream bos = new ByteArrayOutputStream();                            bitmap.compress(Bitmap.CompressFormat.PNG, 80, bos);                            Log.e("StreamActivity", "shouldInterceptRequest: "+(System.currentTimeMillis()-time));* 压缩指定路径的图片，并得到图片对象     *     * @param path bitmap source path     * @return Bitmap {@link android.graphics.Bitmap}     */    public final static Bitmap compressBitmap(String path, int rqsW, int rqsH) {        final BitmapFactory.Options options = new BitmapFactory.Options();        options.inJustDecodeBounds = true;        BitmapFactory.decodeFile(path, options);        options.inSampleSize = caculateInSampleSize(options, rqsW, rqsH);        options.inJustDecodeBounds = false;        return BitmapFactory.decodeFile(path, options);    }/**     * get the orientation of the bitmap {@link android.media.ExifInterface}     * 获取bitmap的方向信息     *     * @param path     * @return     */    public final static int getDegress(String path) {        int degree = 0;        try {            ExifInterface exifInterface = new ExifInterface(path);            int orientation = exifInterface.getAttributeInt(                    ExifInterface.TAG_ORIENTATION,                    ExifInterface.ORIENTATION_NORMAL);            switch (orientation) {                case ExifInterface.ORIENTATION_ROTATE_90:                    degree = 90;                    break;                case ExifInterface.ORIENTATION_ROTATE_180:                    degree = 180;                    break;                case ExifInterface.ORIENTATION_ROTATE_270:                    degree = 270;                    break;            }        } catch (IOException e) {            e.printStackTrace();        }        return degree;    }/**     * rotate the bitmap     *     * @param bitmap     * @param degress     * @return     */    public static Bitmap rotateBitmap(Bitmap bitmap, int degress) {        if (bitmap != null) {            Matrix m = new Matrix();            m.postRotate(degress);            bitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), m, true);            return bitmap;        }        return bitmap;    }

别人的结果：

05-29 17:01:46.350 10313-11784/com.wxxiaomi.ming.webviewcachemodule E/StreamActivity: shouldInterceptRequest: 05-29 17:01:46.410 10313-11784/com.wxxiaomi.ming.webviewcachemodule E/StreamActivity: shouldInterceptRequest: 5505-29 17:01:55.190 10313-11784/com.wxxiaomi.ming.webviewcachemodule E/StreamActivity: shouldInterceptRequest: 05-29 17:01:55.250 10313-11784/com.wxxiaomi.ming.webviewcachemodule E/StreamActivity: shouldInterceptRequest: 55

so，图片压缩的最高境界是先压缩像素后压缩质量，否则将图片文件转为输入流的时候就非常耗时且占用内存很厉害！
over！