如何实现图片模糊

1.项目需求：

​ 当系统软件弹出dialog时候，将当前的页面背景设置成dialog的模糊背景。

2.实现思路：

1. 截屏，获取当前activity的界面
2. 对截取到的图片做高斯模糊处理
3. 将处理好的图片作为背景图

1.截屏的方法

Android 截屏分为四种：View 截屏、WebView 截屏、系统截屏 和 adb 截屏

1.View 截屏

/**
     * 截屏
     *
     * @param activity 截屏的activity
     * @return 截屏图片
     */
    public static Bitmap takeScreenShot(Activity activity) {
        /*获取windows中最顶层的view*/
        View view = activity.getWindow().getDecorView();

        //允许当前窗口保存缓存信息
        view.setDrawingCacheEnabled(true);
        view.buildDrawingCache();

        //获取状态栏高度
        Rect rect = new Rect();
        view.getWindowVisibleDisplayFrame(rect);
        int statusBarHeight = rect.top;

        WindowManager windowManager = activity.getWindowManager();

        //获取屏幕宽和高
        DisplayMetrics outMetrics = new DisplayMetrics();
        windowManager.getDefaultDisplay().getMetrics(outMetrics);
//        int width = outMetrics.widthPixels;
//        int height = outMetrics.heightPixels;
        int width =  activity.getWindow().getDecorView().getRootView().getWidth();
        int height =  activity.getWindow().getDecorView().getRootView().getHeight();

        //去掉状态栏
//        Bitmap bitmap = Bitmap.createBitmap(view.getDrawingCache(), 0, statusBarHeight, width,
//                height - statusBarHeight);
        if (HideBottomMenuUtils.hasNavBar(activity)) {
            HideBottomMenuUtils.hideBottomUIMenu(activity.getWindow());
        }

        Bitmap bitmap = Bitmap.createBitmap( width, height, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmap);
        view.draw(canvas);

        //销毁缓存信息
        view.destroyDrawingCache();
        view.setDrawingCacheEnabled(false);

        return bitmap;
    }

View 截图是将当前 View 界面截取下来，而对于屏幕上其他信息比如：状态栏或其他应用的界面将无法截取。

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Rect;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.View;
import android.view.WindowManager;
/**
* @desc  设置模糊背景 
* @author luxi 
* @date 2023/3/14 9:09
*/
public class FastBlurUtility {
    /**

   * 获得模糊化的背景图片

        * @param activity 获取模糊化的背景activity
           @return 模糊化的背景图片
               */
              public static Bitmap getBlurBackgroundDrawer(Activity activity) {
          Bitmap bmp = takeScreenShot(activity);
          return startBlurBackground(bmp);
              }

​    /**

   * 截屏

        * @param activity 截屏的activity
           @return 截屏图片
               */
              public static Bitmap takeScreenShot(Activity activity) {
          /*获取windows中最顶层的view*/
          View view = activity.getWindow().getDecorView();

     //允许当前窗口保存缓存信息
     view.setDrawingCacheEnabled(true);
     view.buildDrawingCache();

     //获取状态栏高度
     Rect rect = new Rect();
     view.getWindowVisibleDisplayFrame(rect);
     int statusBarHeight = rect.top;

     WindowManager windowManager = activity.getWindowManager();

     //获取屏幕宽和高
     DisplayMetrics outMetrics = new DisplayMetrics();
     windowManager.getDefaultDisplay().getMetrics(outMetrics);
     //        int width = outMetrics.widthPixels;
     //        int height = outMetrics.heightPixels;
     int width =  activity.getWindow().getDecorView().getRootView().getWidth();
     int height =  activity.getWindow().getDecorView().getRootView().getHeight();

     //去掉状态栏
     //        Bitmap bitmap = Bitmap.createBitmap(view.getDrawingCache(), 0, statusBarHeight, width,
     //                height - statusBarHeight);
     if (HideBottomMenuUtils.hasNavBar(activity)) {
         HideBottomMenuUtils.hideBottomUIMenu(activity.getWindow());
     }

     Bitmap bitmap = Bitmap.createBitmap( width, height, Bitmap.Config.ARGB_8888);
     Canvas canvas = new Canvas(bitmap);
     view.draw(canvas);

     //销毁缓存信息
     view.destroyDrawingCache();
     view.setDrawingCacheEnabled(false);

     return bitmap;
         }

    private static Bitmap startBlurBackground(Bitmap bkg) {
        long startMs = System.currentTimeMillis();
        float radius = 8; //模糊程度
        Bitmap overlay = fastblur(small(bkg), (int) radius);
        Log.i("FastBlurUtility", "=====blur time:" + (System.currentTimeMillis() - startMs));
        return big(overlay);
    }

    /**

   * 放大图片

        * @param bitmap 需要放大的图片
           @return 放大的图片
               */
              private static Bitmap big(Bitmap bitmap) {
          Matrix matrix = new Matrix();
          matrix.postScale(4f, 4f);
          Bitmap resizeBmp = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
          return resizeBmp;
              }

    /**

   * 缩小图片

        * @param bitmap 需要缩小的图片
           @return 缩小的图片
               */
              private static Bitmap small(Bitmap bitmap) {
          Matrix matrix = new Matrix();
          matrix.postScale(0.25f, 0.25f);
          Bitmap resizeBmp = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
          return resizeBmp;
              }

​    /**

   * 将图片模糊化

        * @param sentBitmap 需要模糊的图片
           @param radius     模糊程度
             * @return 模糊后的图片
               /
                   private static Bitmap fastblur(Bitmap sentBitmap, int radius) {
               Bitmap 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++) {
               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);
                   }







}