安卓 bitmap生成縮略圖

    /**
     * 生成縮略圖
     * 縮略圖是將原圖等比壓縮，壓縮後寬、高中較小的一個等於198像素  
     */
    private Bitmap getThumb(String path){
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(path, options);
        int reqWidth, reqHeight, width=options.outWidth, height=options.outHeight;
        if (width > height){
            reqWidth = 198;
            reqHeight = (reqWidth * height)/width;
        }else{
            reqHeight = 198;
            reqWidth = (width * reqHeight)/height;
        }
        int inSampleSize = 1;
        if (height > reqHeight || width > reqWidth) {
            final int halfHeight = height / 2;
            final int halfWidth = width / 2;
            while ((halfHeight / inSampleSize) > reqHeight
                    && (halfWidth / inSampleSize) > reqWidth) {
                inSampleSize *= 2;
            }
        }
        try{
            options.inSampleSize = inSampleSize;
            options.inJustDecodeBounds = false;
            Matrix mat = new Matrix();
            Bitmap bitmap = BitmapFactory.decodeFile(path, options);
            ExifInterface ei =  new ExifInterface(path);
            int orientation = ei.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);
            switch(orientation) {
                case ExifInterface.ORIENTATION_ROTATE_90:
                    mat.postRotate(90);
                    break;
                case ExifInterface.ORIENTATION_ROTATE_180:
                    mat.postRotate(180);
                    break;
            }
//            Log.e("test","bitmap.getWidth():"+bitmap.getWidth()+",,bitmap.getHeight():"+bitmap.getHeight());
            return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), mat, true);
        }catch (IOException e){
            return null;
        }
    }