图片转圆角（saveLayer、restore）

public static Bitmap getRoundedCornerBitmap(Bitmap bitmap, float roundPx) {
		int x = bitmap.getWidth();
		int y = bitmap.getHeight();
		float[] mOuter = new float[] { roundPx, roundPx, roundPx, roundPx,
				roundPx, roundPx, roundPx, roundPx };
		// 根据源文件新建一个darwable对象
		Drawable imageDrawable = new BitmapDrawable(bitmap);

		// 新建一个新的输出图片
		Bitmap output = Bitmap.createBitmap(x, y, Bitmap.Config.ARGB_8888);
		Canvas canvas = new Canvas(output);

		// 新建一个矩形
		RectF outerRect = new RectF(0, 0, x, y);
		Path mPath = new Path();
		// 创建一个圆角矩形路径
		mPath.addRoundRect(outerRect, mOuter, Path.Direction.CW);

		// 画出一个红色的圆角矩形
		Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
		paint.setColor(Color.RED);
		paint.setAntiAlias(true);
		canvas.drawPath(mPath, paint);
		// 设置绘图两层交汇时的模式
		paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
		// 设置绘图区域（在那个区域内绘图）
		imageDrawable.setBounds(0, 0, x, y);
		// 将用于绘制图片的图层拷贝到单独图层并压入图层栈
		canvas.saveLayer(outerRect, paint, Canvas.ALL_SAVE_FLAG);
		// 将源图片绘制到这个拷贝的图片图层上
		imageDrawable.draw(canvas);
		// 将图片图层退出栈并将图像绘制到矩形的那一层
		canvas.restore();
		return output;
	}

public static Bitmap getCircleBitmap(Bitmap bitmap, float roundPx) {
		Drawable imageDrawable = new BitmapDrawable(bitmap);
		// 新建一个新的输出图片
		Bitmap output = Bitmap.createBitmap((int)roundPx, (int)roundPx, Bitmap.Config.ARGB_8888);
		Canvas canvas = new Canvas(output);
		Path mPath = new Path();
		mPath.addCircle(roundPx/2, roundPx/2, roundPx/2, Path.Direction.CW);

		// 画出一个红色的圆角矩形
		Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
		paint.setColor(Color.RED);
		paint.setAntiAlias(true);
		canvas.drawPath(mPath, paint);
		// 设置绘图两层交汇时的模式
		paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
		// 设置绘图区域（在那个区域内绘图）
		imageDrawable.setBounds(0, 0, (int)roundPx, (int)roundPx);
		// 将用于绘制图片的图层压入图层栈
		canvas.saveLayer(0, 0, (int)roundPx, (int)roundPx, paint, Canvas.ALL_SAVE_FLAG);
		// 将源图片绘制到这个圆角矩形上
		imageDrawable.draw(canvas);
		// 将图片图层退出栈并将图像绘制到矩形的那一层
		canvas.restore();
		return output;
	}

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;
	}