合成两张图片的代码

[GitHub 源码地址](https://github.com/heqiangflytosky/AndroidUtils)

	/**
	 * 将mask覆盖在bitmap之上，并合成指定大小的图片
	 * @param bitmap
	 * @param mask
	 * @param destW
	 * @param desH
	 * @return
	 */
	public static Bitmap maskBitmap(Bitmap bitmap, Bitmap mask, int destW, int desH) {
		if (null == bitmap || mask == null) {
			return null;
		}

		int widthMask = mask.getWidth();
		int heightMask = mask.getHeight();

		int widthOrg = bitmap.getWidth();
		int heightOrg = bitmap.getHeight();

		int width = Math.max(widthMask, widthOrg);
		int height = Math.max(heightMask, heightOrg);

		// 定义期望大小的bitmap
		Bitmap dstBmp = Bitmap.createBitmap(width, height, Config.ARGB_8888);
		Canvas canvas = new Canvas(dstBmp);
		Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);

		// 定义需要绘制的某图片上的那一部分矩形空间
		Rect srcMask = new Rect(0, 0, widthMask, heightMask);
		// 定义需要将上面的矩形绘制成新的矩形大小
		Rect dstMask = new Rect((width - widthMask) / 2,
				(height - heightMask) / 2, (width + widthMask) / 2,
				(height + heightMask) / 2);
		canvas.drawBitmap(mask, srcMask, dstMask, paint);
		paint.setXfermode(new PorterDuffXfermode(Mode.DST_OVER));

		// 定义需要绘制的某图片上的那一部分矩形空间
		Rect srcOrg = new Rect(0, 0, widthOrg, heightOrg);
		// mx3绘制成100*100 mx2绘制成80*80
		// 定义需要将上面的矩形绘制成新的矩形大小
		Rect dstOrg = new Rect((width - destW) / 2,
				(height - desH) / 2, (width + destW) / 2,
				(height + desH) / 2);
		// 在已经绘制的mask上叠加bitmap
		canvas.drawBitmap(bitmap, srcOrg, dstOrg, paint);
		return dstBmp;
	}