实现图片毛玻璃特效

今天看见一个大神写的毛玻璃特效实现方法，只调用了两个方法，很简洁，就拿来试了一下。

1、首先是StackBlur模糊算法；
把大神的java类照搬过来：

package com.example.aeroglass;import android.graphics.Bitmap;/** * Created by paveld on 3/6/14. */public class FastBlur {    public static Bitmap doBlur(Bitmap sentBitmap, int radius, boolean canReuseInBitmap) {        // Stack Blur v1.0 from        // http://www.quasimondo.com/StackBlurForCanvas/StackBlurDemo.html        //        // Java Author: Mario Klingemann <mario at="" quasimondo.com="">        // http://incubator.quasimondo.com        // created Feburary 29, 2004        // Android port : Yahel Bouaziz <yahel at="" kayenko.com="">        // http://www.kayenko.com        // ported april 5th, 2012        // This is a compromise between Gaussian Blur and Box blur        // It creates much better looking blurs than Box Blur, but is        // 7x faster than my Gaussian Blur implementation.        //        // I called it Stack Blur because this describes best how this        // filter works internally: it creates a kind of moving stack        // of colors whilst scanning through the image. Thereby it        // just has to add one new block of color to the right side        // of the stack and remove the leftmost color. The remaining        // colors on the topmost layer of the stack are either added on        // or reduced by one, depending on if they are on the right or        // on the left side of the stack.        //        // If you are using this algorithm in your code please add        // the following line:        //        // Stack Blur Algorithm by Mario Klingemann <[e-mail]>        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);    }}

这个算法怎么算的，嗯，反正我没看懂。
doBlur(Bitmap sentBitmap, int radius, boolean canReuseInBitmap)
调用此方法，会返回一个模糊好的bitmap

2、为了防止过大的图造成内存溢出，对图片进行一个压缩。
使用Bitmap.createScaledBitmap（Bitmap src, int dstWidth, int dstHeight, boolean filter）；方法
里面有四个参数，除了第四个参数是否平滑锯齿，别的很直接。这里反正就是要模糊的图片，直接false；

3、实际使用中，我出现了3个bug，并对代码做了一些修改；
这里没有考虑多线程的情况，也没有做防止压缩后有可能出现oom的情况；

/**     * @param bitmap 要模糊图片的bitmap     * @param scaleRatio 压缩比，不能为0     * @return 模糊好的bitmap     */    public static Bitmap blur(Bitmap bitmap, int scaleRatio) {        int blurRadius = 8;        int width = bitmap.getWidth() / scaleRatio;        int height = bitmap.getHeight() / scaleRatio;        while(true){            //width和height都不可为0            if (width <= 1 && height <= 1) {                scaleRatio -= 1;                width = bitmap.getWidth() / scaleRatio;                height = bitmap.getHeight() / scaleRatio;            }else{                Bitmap scaledBitmap = Bitmap.createScaledBitmap(bitmap, width, height,                        false);                /**                 * 此处将最后一个参数设置为false，会copy一个可变类型的bitmap，                 * 因为fastBlur的doBlur算法最后调用的bitmap.setPixels()方法，                 * 如果bitmap为不可变类型，会抛IllegalStateException;                 */                Bitmap blurBitmap = FastBlur.doBlur(scaledBitmap, blurRadius, false);                return blurBitmap;            }        }    }

上面的三处注释就是我遇到的bug

3.1 int scaleRatio 这个参数不能为0，分母嘛，这个不说了；
3.2 Bitmap.createScaledBitmap(bitmap, width, height,
false);
这个方法里面传入的width，height不能为0，要创建一个bitmap，宽或者高为0 肯定是创建不出来的；
我用while循环处理了一下，每次把分母减1，直到宽高都不为0， 感觉不太好，好想有大神指导一下。
3.3 这个是调用Bitmap的setPixels（）方法时，如果bitmap不可变，会抛IllegalStateException；

public void setPixels(@ColorInt int[] pixels, int offset, int stride,            int x, int y, int width, int height) {        checkRecycled("Can't call setPixels() on a recycled bitmap");        if (!isMutable()) {            throw new IllegalStateException();        }        if (width == 0 || height == 0) {            return; // nothing to do        }        checkPixelsAccess(x, y, width, height, offset, stride, pixels);        nativeSetPixels(mFinalizer.mNativeBitmap, pixels, offset, stride,                        x, y, width, height);    }

这个解决也很简单，copy一个可变的bitmap就好了。
在FastBlur的doBlur(Bitmap sentBitmap, int radius, boolean canReuseInBitmap)方法里，最后一个参数就是是否重用bitmap。
如果传入false，就会copy一份可变的bitmap。

Bitmap bitmap;        if (canReuseInBitmap) {            bitmap = sentBitmap;        } else {            bitmap = sentBitmap.copy(sentBitmap.getConfig(), true);        }

这个让我比较纳闷的是，我之前设置的true，不copybitmap，没有问题，然后我换了张图片，没有改变代码，就出现了IllegalStateException异常，难道不同的图片格式出来的bitmap有的可变有的不可变，奇怪。

借鉴了两个博文，下面是链接
http://www.jcodecraeer.com/a/anzhuokaifa/androidkaifa/2016/0312/4049.html
http://www.2cto.com/kf/201410/341596.html