[移动开发]Android 高斯模糊方法集

工具类

public class GaussianBlurUtil {

    private final static String TAG = "GaussianBlurUtil";

    /**
     * first method : RenderScript
     * 优点：原生API、效率高，在C/C++ 层做处理
     * 缺点：API > 17 才可以用、用兼容包的话，会导致APK 体积增大，support包约160k
     * @param context
     * @param source
     * @param radius
     * @param scale 可以为1/2、1/4、1/8(依据经验，最佳)
     * @return
     */
    public static Bitmap rsBlur(Context context,Bitmap source,int radius,float scale){

        // 图片缩小，提高效率
        int width = Math.round(source.getWidth() * scale);
        int height = Math.round(source.getHeight() * scale);
        Bitmap inputBmp = Bitmap.createScaledBitmap(source,width,height,false);

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

        //(1) 初始化 RenderScript
        RenderScript renderScript =  RenderScript.create(context);

        Log.i(TAG,"scale size:"+inputBmp.getWidth()+"*"+inputBmp.getHeight());

        //(2) 使用 createFromBitmap 和 createTyped 来创建 Allocation
        final Allocation input = Allocation.createFromBitmap(renderScript,inputBmp);
        final Allocation output = Allocation.createTyped(renderScript,input.getType());
        //(3) 创建 ScriptIntrinsicBlur，用来进行高斯模糊处理
        ScriptIntrinsicBlur scriptIntrinsicBlur = ScriptIntrinsicBlur.create(renderScript, Element.U8_4(renderScript));
        //(4) 填充数据到 Allocation
        scriptIntrinsicBlur.setInput(input);
        //(5) 设置模糊半径，取值范围为(0,25]
        scriptIntrinsicBlur.setRadius(radius);
        //(6) 启动内核，调用 forEach 方法进行模糊处理
        scriptIntrinsicBlur.forEach(output);
        //(7) 从 Allocation 中拷贝数据
        output.copyTo(inputBmp);
        //(8) 销毁 RenderScript 对象
        renderScript.destroy();
        return inputBmp;
    }

    /**
     * second method : FastBlur
     * 优点：不用兼容版本、不用引用第三方包，不会增加APK 大小
     * 缺点：效率低，在Java 层做处理、将Bitmap 全部加载到内存中，较大图片容易OOM
     * @param sentBitmap
     * @param scale 可以为1/2、1/4、1/8(依据经验，最佳)
     * @param radius
     * @return
     */
    public static Bitmap fastBlur(Bitmap sentBitmap, float scale, int radius) {
        return FastBlur.doBlur(sentBitmap,scale,radius);
    }
}

package com.example.test.Utils;

import android.graphics.Bitmap;
import android.util.Log;

public class FastBlur {

    public static Bitmap doBlur(Bitmap sentBitmap, float scale, int radius) {

        // 缩小图片，提高效率
        int width = Math.round(sentBitmap.getWidth() * scale);
        int height = Math.round(sentBitmap.getHeight() * scale);
        sentBitmap = Bitmap.createScaledBitmap(sentBitmap, width, height, false);

        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++) {
                // 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);
    }
}

参考文章：
Android 图片高斯模糊解决方案