图片圆角效果

public static Bitmap getRoundCornerImage(Bitmap bitmap, int roundPixels)
    {
        //创建一个和原始图片一样大小位图
        Bitmap roundConcerImage = Bitmap.createBitmap(bitmap.getWidth(),
                bitmap.getHeight(), Config.ARGB_8888);
        //创建带有位图roundConcerImage的画布
        Canvas canvas = new Canvas(roundConcerImage);
        //创建画笔
        Paint paint = new Paint();
        //创建一个和原始图片一样大小的矩形
        Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
        RectF rectF = new RectF(rect);
        // 去锯齿
        paint.setAntiAlias(true);
        //画一个和原始图片一样大小的圆角矩形
        canvas.drawRoundRect(rectF, roundPixels, roundPixels, paint);
        //设置相交模式
        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
        //把图片画到矩形去
        canvas.drawBitmap(bitmap, null, rect, paint);
        return roundConcerImage;
    }