Android截屏并对图片做高斯模糊处理

这几天项目中需要模仿一下iOS版本的微博菜单弹出界面，如下图：



用微博的同学都知道这个效果吧，这篇文章先实现模糊效果，进入、退出动画后面文章分析；

一、说一下实现思路，很简单的：
1、截图：就是获取我们app得截图
获取我们Activity得根view即DecorView，关于DecorView，sdk里面是这么说明的：

Retrieve the top-level window decor view (containing the standard window frame/decorations and the client's content inside of that), which can be added as a window to the window manager. 

就是说获取最顶层的window，可以添加到window manager里面；
拿到view之后可以调用view的getDrawingCache方法获取bitmap截图；

2、对图片做高斯模糊；
高斯模糊在Photoshop里面用的比较多，可以用来去痘痘。
大致原理是：对指定像素和其周围像素进行加权平均来得到最终结果，使用高斯分布作为滤波器。
这儿可以了解详细的算法原理：http://www.ruanyifeng.com/blog/2012/11/gaussian_blur.html


二、代码实现：
代码比较简单，我自己加了注释贴出来了：

	private void applyBlur() {
		View view = getWindow().getDecorView();
		view.setDrawingCacheEnabled(true);
		view.buildDrawingCache(true);
		/**
		 * 获取当前窗口快照，相当于截屏
		 */
		Bitmap bmp1 = view.getDrawingCache();
		int height = getOtherHeight();
		/**
		 * 除去状态栏和标题栏
		 */
		Bitmap bmp2 = Bitmap.createBitmap(bmp1, 0, height,bmp1.getWidth(), bmp1.getHeight() - height);
		blur(bmp2, text);
	}

	@SuppressLint("NewApi")
	private void blur(Bitmap bkg, View view) {
		long startMs = System.currentTimeMillis();
		float scaleFactor = 8;//图片缩放比例；
		float radius = 20;//模糊程度

		Bitmap overlay = Bitmap.createBitmap(
				(int) (view.getMeasuredWidth() / scaleFactor),
				(int) (view.getMeasuredHeight() / scaleFactor),
				Bitmap.Config.ARGB_8888);
		Canvas canvas = new Canvas(overlay);
		canvas.translate(-view.getLeft() / scaleFactor, -view.getTop()/ scaleFactor);
		canvas.scale(1 / scaleFactor, 1 / scaleFactor);
		Paint paint = new Paint();
		paint.setFlags(Paint.FILTER_BITMAP_FLAG);
		canvas.drawBitmap(bkg, 0, 0, paint);

		
		overlay = FastBlur.doBlur(overlay, (int) radius, true);
		view.setBackground(new BitmapDrawable(getResources(), overlay));
		/**
		 * 打印高斯模糊处理时间，如果时间大约16ms，用户就能感到到卡顿，时间越长卡顿越明显，如果对模糊完图片要求不高，可是将scaleFactor设置大一些。
		 */
		Log.i("jerome", "blur time:" + (System.currentTimeMillis() - startMs));
	}

	/**
	 * 获取系统状态栏和软件标题栏，部分软件没有标题栏，看自己软件的配置；
	 * @return
	 */
	private int getOtherHeight() {
		Rect frame = new Rect();
		getWindow().getDecorView().getWindowVisibleDisplayFrame(frame);
		int statusBarHeight = frame.top;
		int contentTop = getWindow().findViewById(Window.ID_ANDROID_CONTENT).getTop();
		int titleBarHeight = contentTop - statusBarHeight;
		return statusBarHeight + titleBarHeight;
	}

我这里用了外国开源项目中的一个Java算法，地址：https://github.com/paveldudka/blurring

package com.jerome.popdemo;

import android.graphics.Bitmap;

/**
 * Created by paveld on 3/6/14.
 */
public class FastBlur {

	public static Bitmap doBlur(Bitmap sentBitmap, int radius,
			boolean canReuseInBitmap) {
		Bitmap bitmap;
		if (canReuseInBitmap) {
			bitmap = sentBitmap;
		} else {
			bitmap = sentBitmap.copy(sentBitmap.getConfig(), true);
		}

		if (radius < 1) {
			return (null);
		}

		int w = bitmap.getWidth();
		int h = bitmap.getHeight();

		int[] pix = new int[w * h];
		bitmap.getPixels(pix, 0, w, 0, 0, w, h);

		int wm = w - 1;
		int hm = h - 1;
		int wh = w * h;
		int div = radius + radius + 1;

		int r[] = new int[wh];
		int g[] = new int[wh];
		int b[] = new int[wh];
		int rsum, gsum, bsum, x, y, i, p, yp, yi, yw;
		int vmin[] = new int[Math.max(w, h)];

		int divsum = (div + 1) >> 1;
		divsum *= divsum;
		int dv[] = new int[256 * divsum];
		for (i = 0; i < 256 * divsum; i++) {
			dv[i] = (i / divsum);
		}

		yw = yi = 0;

		int[][] stack = new int[div][3];
		int stackpointer;
		int stackstart;
		int[] sir;
		int rbs;
		int r1 = radius + 1;
		int routsum, goutsum, boutsum;
		int rinsum, ginsum, binsum;

		for (y = 0; y < h; y++) {
			rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
			for (i = -radius; i <= radius; i++) {
				p = pix[yi + Math.min(wm, Math.max(i, 0))];
				sir = stack[i + radius];
				sir[0] = (p & 0xff0000) >> 16;
				sir[1] = (p & 0x00ff00) >> 8;
				sir[2] = (p & 0x0000ff);
				rbs = r1 - Math.abs(i);
				rsum += sir[0] * rbs;
				gsum += sir[1] * rbs;
				bsum += sir[2] * rbs;
				if (i > 0) {
					rinsum += sir[0];
					ginsum += sir[1];
					binsum += sir[2];
				} else {
					routsum += sir[0];
					goutsum += sir[1];
					boutsum += sir[2];
				}
			}
			stackpointer = radius;

			for (x = 0; x < w; x++) {

				r[yi] = dv[rsum];
				g[yi] = dv[gsum];
				b[yi] = dv[bsum];

				rsum -= routsum;
				gsum -= goutsum;
				bsum -= boutsum;

				stackstart = stackpointer - radius + div;
				sir = stack[stackstart % div];

				routsum -= sir[0];
				goutsum -= sir[1];
				boutsum -= sir[2];

				if (y == 0) {
					vmin[x] = Math.min(x + radius + 1, wm);
				}
				p = pix[yw + vmin[x]];

				sir[0] = (p & 0xff0000) >> 16;
				sir[1] = (p & 0x00ff00) >> 8;
				sir[2] = (p & 0x0000ff);

				rinsum += sir[0];
				ginsum += sir[1];
				binsum += sir[2];

				rsum += rinsum;
				gsum += ginsum;
				bsum += binsum;

				stackpointer = (stackpointer + 1) % div;
				sir = stack[(stackpointer) % div];

				routsum += sir[0];
				goutsum += sir[1];
				boutsum += sir[2];

				rinsum -= sir[0];
				ginsum -= sir[1];
				binsum -= sir[2];

				yi++;
			}
			yw += w;
		}
		for (x = 0; x < w; x++) {
			rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
			yp = -radius * w;
			for (i = -radius; i <= radius; i++) {
				yi = Math.max(0, yp) + x;

				sir = stack[i + radius];

				sir[0] = r[yi];
				sir[1] = g[yi];
				sir[2] = b[yi];

				rbs = r1 - Math.abs(i);

				rsum += r[yi] * rbs;
				gsum += g[yi] * rbs;
				bsum += b[yi] * rbs;

				if (i > 0) {
					rinsum += sir[0];
					ginsum += sir[1];
					binsum += sir[2];
				} else {
					routsum += sir[0];
					goutsum += sir[1];
					boutsum += sir[2];
				}

				if (i < hm) {
					yp += w;
				}
			}
			yi = x;
			stackpointer = radius;
			for (y = 0; y < h; y++) {
				// Preserve alpha channel: ( 0xff000000 & pix[yi] )
				pix[yi] = (0xff000000 & pix[yi]) | (dv[rsum] << 16)
						| (dv[gsum] << 8) | dv[bsum];

				rsum -= routsum;
				gsum -= goutsum;
				bsum -= boutsum;

				stackstart = stackpointer - radius + div;
				sir = stack[stackstart % div];

				routsum -= sir[0];
				goutsum -= sir[1];
				boutsum -= sir[2];

				if (x == 0) {
					vmin[y] = Math.min(y + r1, hm) * w;
				}
				p = x + vmin[y];

				sir[0] = r[p];
				sir[1] = g[p];
				sir[2] = b[p];

				rinsum += sir[0];
				ginsum += sir[1];
				binsum += sir[2];

				rsum += rinsum;
				gsum += ginsum;
				bsum += binsum;

				stackpointer = (stackpointer + 1) % div;
				sir = stack[stackpointer];

				routsum += sir[0];
				goutsum += sir[1];
				boutsum += sir[2];

				rinsum -= sir[0];
				ginsum -= sir[1];
				binsum -= sir[2];

				yi += w;
			}
		}

		bitmap.setPixels(pix, 0, w, 0, 0, w, h);

		return (bitmap);
	}
}

如果用C/C++实现jni调用，效果会高一些，可以参考：https://github.com/qiujuer/ImageBlurring/blob/master/README-ZH.md

/*************************************************
Copyright:  Copyright QIUJUER 2013.
Author:		Qiujuer
Date:		2014-04-18
Description:实现图片模糊处理
**************************************************/
#include<malloc.h>

#define ABS(a) ((a)<(0)?(-a):(a))
#define MAX(a,b) ((a)>(b)?(a):(b))
#define MIN(a,b) ((a)<(b)?(a):(b))

/*************************************************
Function:		StackBlur(堆栈模糊)
Description:    使用堆栈方式进行图片像素模糊处理
Calls:          malloc
Table Accessed: NULL
Table Updated:	NULL
Input:          像素点集合，图片宽，图片高，模糊半径
Output:         返回模糊后的像素点集合
Return:         返回模糊后的像素点集合
Others:         NULL
*************************************************/
static int* StackBlur(int* pix, int w, int h, int radius) {
	int wm = w - 1;
	int hm = h - 1;
	int wh = w * h;
	int div = radius + radius + 1;

	int *r = (int *)malloc(wh * sizeof(int));
	int *g = (int *)malloc(wh * sizeof(int));
	int *b = (int *)malloc(wh * sizeof(int));
	int rsum, gsum, bsum, x, y, i, p, yp, yi, yw;

	int *vmin = (int *)malloc(MAX(w,h) * sizeof(int));

	int divsum = (div + 1) >> 1;
	divsum *= divsum;
	int *dv = (int *)malloc(256 * divsum * sizeof(int));
	for (i = 0; i < 256 * divsum; i++) {
		dv[i] = (i / divsum);
	}

	yw = yi = 0;

	int(*stack)[3] = (int(*)[3])malloc(div * 3 * sizeof(int));
	int stackpointer;
	int stackstart;
	int *sir;
	int rbs;
	int r1 = radius + 1;
	int routsum, goutsum, boutsum;
	int rinsum, ginsum, binsum;

	for (y = 0; y < h; y++) {
		rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
		for (i = -radius; i <= radius; i++) {
			p = pix[yi + (MIN(wm, MAX(i, 0)))];
			sir = stack[i + radius];
			sir[0] = (p & 0xff0000) >> 16;
			sir[1] = (p & 0x00ff00) >> 8;
			sir[2] = (p & 0x0000ff);

			rbs = r1 - ABS(i);
			rsum += sir[0] * rbs;
			gsum += sir[1] * rbs;
			bsum += sir[2] * rbs;
			if (i > 0) {
				rinsum += sir[0];
				ginsum += sir[1];
				binsum += sir[2];
			}
			else {
				routsum += sir[0];
				goutsum += sir[1];
				boutsum += sir[2];
			}
		}
		stackpointer = radius;

		for (x = 0; x < w; x++) {

			r[yi] = dv[rsum];
			g[yi] = dv[gsum];
			b[yi] = dv[bsum];

			rsum -= routsum;
			gsum -= goutsum;
			bsum -= boutsum;

			stackstart = stackpointer - radius + div;
			sir = stack[stackstart % div];

			routsum -= sir[0];
			goutsum -= sir[1];
			boutsum -= sir[2];

			if (y == 0) {
				vmin[x] = MIN(x + radius + 1, wm);
			}
			p = pix[yw + vmin[x]];

			sir[0] = (p & 0xff0000) >> 16;
			sir[1] = (p & 0x00ff00) >> 8;
			sir[2] = (p & 0x0000ff);

			rinsum += sir[0];
			ginsum += sir[1];
			binsum += sir[2];

			rsum += rinsum;
			gsum += ginsum;
			bsum += binsum;

			stackpointer = (stackpointer + 1) % div;
			sir = stack[(stackpointer) % div];

			routsum += sir[0];
			goutsum += sir[1];
			boutsum += sir[2];

			rinsum -= sir[0];
			ginsum -= sir[1];
			binsum -= sir[2];

			yi++;
		}
		yw += w;
	}
	for (x = 0; x < w; x++) {
		rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
		yp = -radius * w;
		for (i = -radius; i <= radius; i++) {
			yi = MAX(0, yp) + x;

			sir = stack[i + radius];

			sir[0] = r[yi];
			sir[1] = g[yi];
			sir[2] = b[yi];

			rbs = r1 - ABS(i);

			rsum += r[yi] * rbs;
			gsum += g[yi] * rbs;
			bsum += b[yi] * rbs;

			if (i > 0) {
				rinsum += sir[0];
				ginsum += sir[1];
				binsum += sir[2];
			}
			else {
				routsum += sir[0];
				goutsum += sir[1];
				boutsum += sir[2];
			}

			if (i < hm) {
				yp += w;
			}
		}
		yi = x;
		stackpointer = radius;
		for (y = 0; y < h; y++) {
			// Preserve alpha channel: ( 0xff000000 & pix[yi] )
			pix[yi] = (0xff000000 & pix[yi]) | (dv[rsum] << 16) | (dv[gsum] << 8) | dv[bsum];

			rsum -= routsum;
			gsum -= goutsum;
			bsum -= boutsum;

			stackstart = stackpointer - radius + div;
			sir = stack[stackstart % div];

			routsum -= sir[0];
			goutsum -= sir[1];
			boutsum -= sir[2];

			if (x == 0) {
				vmin[y] = MIN(y + r1, hm) * w;
			}
			p = x + vmin[y];

			sir[0] = r[p];
			sir[1] = g[p];
			sir[2] = b[p];

			rinsum += sir[0];
			ginsum += sir[1];
			binsum += sir[2];

			rsum += rinsum;
			gsum += ginsum;
			bsum += binsum;

			stackpointer = (stackpointer + 1) % div;
			sir = stack[stackpointer];

			routsum += sir[0];
			goutsum += sir[1];
			boutsum += sir[2];

			rinsum -= sir[0];
			ginsum -= sir[1];
			binsum -= sir[2];

			yi += w;
		}
	}

	free(r);
	free(g);
	free(b);
	free(vmin);
	free(dv);
	free(stack);
	return(pix);
}

最后来一张屌丝做demo专业效果图：