android 图片放大的处理

场景：从网络上下载下来的小图片，直接使用设置某些区域的大小的时候，会使得图片变形。这个时候，最佳的解决方案是，在图片的清晰度可以容忍的情况下，将图片进行拉升放大处理，处理过程如下：

Bitmap originalBitmap = originalBitmap1;
		int bw = originalBitmap.getWidth();
		int bh = originalBitmap.getHeight();
		 float scaleWidth = expectedWidth*1.0F / bw;
         float scaleHeight = expectedHeight*1.0F / bh;
         //取伸缩小的值
         float scale = scaleHeight < scaleWidth ?  scaleHeight : scaleWidth;
         
         Matrix matrix = new Matrix();
         matrix.postScale(scale, scale);
         Bitmap resizedBitmap = Bitmap.createBitmap(originalBitmap, 0, 0, bw, bh, matrix, true);
         // 绘制背景图片
         Bitmap mBitmap = Bitmap.createBitmap(expectedWidth, expectedHeight, Bitmap.Config.RGB_565);
         Canvas mCanvas = new Canvas(mBitmap);
         Paint bitmapPaint = new Paint(Paint.FILTER_BITMAP_FLAG);
         // 设定背景颜色
         mCanvas.drawColor(0xff000000);
         float left = expectedWidth / 2 - bw * scale / 2;
         float top = expectedHeight / 2 - bh * scale / 2;
         mCanvas.drawBitmap(resizedBitmap,left ,top , bitmapPaint);
         mCanvas.save();
         return mBitmap;