Android 模糊效果 FastBlur

import android.graphics.Bitmap;

import android.graphics.Canvas;

import android.graphics.Paint;

import android.graphics.drawable.BitmapDrawable;

import android.util.Log;

import android.view.View;

import android.view.ViewTreeObserver;

 

public class FastBlur {



    public static void applyBlur(final View v) {

        v.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {

            @Override

            public boolean onPreDraw() {

                v.getViewTreeObserver().removeOnPreDrawListener(this);

                v.buildDrawingCache();

                Bitmap bmp = v.getDrawingCache();

                blur(bmp, v);

                return true;

            }

        });

    }



    public static void blur(Bitmap bkg, View view) {

        long startMs = System.currentTimeMillis();

        float scaleFactor = 1;

        float radius = 20;

        scaleFactor = 8;

        radius = 2;



        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.setBackgroundDrawable(new BitmapDrawable(view.getResources(), overlay));

        Log.e("TAG", System.currentTimeMillis() - startMs + "ms");

    }



    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);

    }

}