Android部分开源项目源码分析之--ListView 图片顶部模糊的高斯处理

前言：

我们可以看到APP"在路上"上面的 高斯的模糊的处理的效果，在下拉的时候，图像就会变的清晰， 看到了这个效果，我也开始对其进行模仿。

      

我做的效果

设计的思路：

我开始在想直接用高斯模糊处理图片，在图片不断的下拉的过程中也对图片的进行高斯处理达到实时对图片进行高斯模糊处理，达到 下拉到最下面的 图片变的clear，在拉动的过程中，图片的模糊度也随之变化。

但是，高斯模糊处理图片是比较消耗时间的。so 上面这样处理将会是很卡的。然而在“在路上”的这个APP却一点也不存在卡的现象。

so... 经过在网上的查询，发现 https://github.com/PomepuyN/BlurEffectForAndroidDesign ，经过研究发现

自己想上面的效果 实现是：

1、在图片的位置放置上两张图片，高斯模糊处理的在上面，下面放置一张清晰的图片

2、在下拉动的过程中间，把高斯模糊处理的的透明度不断的降低。（so，其背后的图片就将会清晰，而凸显出来）

3、在开屏幕的时候，图片就会自动缩回去。在缩回去的时候，读取当前的alpha 的值，从当前值开始，到透明度为1的变化。

       FloatEvaluator e = new FloatEvaluator();
float img_logo_img_blur_alpha = e.evaluate(aplah, startAlpha, 1f);

高斯模糊处理源码：

/** * 参考 ：https://github.com/PomepuyN/BlurEffectForAndroidDesign * @author Administrator * */public class Blur {private static final String TAG = "Blur";@SuppressLint("NewApi")public static Bitmap fastblur(Context context, Bitmap sentBitmap, int radius) {if (VERSION.SDK_INT > 16) {System.out.println("VERSION.SDK_INT "+VERSION.SDK_INT);Bitmap bitmap = sentBitmap.copy(sentBitmap.getConfig(), true);final RenderScript rs = RenderScript.create(context);final Allocation input = Allocation.createFromBitmap(rs, sentBitmap, Allocation.MipmapControl.MIPMAP_NONE,Allocation.USAGE_SCRIPT);final Allocation output = Allocation.createTyped(rs, input.getType());final ScriptIntrinsicBlur script = ScriptIntrinsicBlur.create(rs, Element.U8_4(rs));script.setRadius(radius /* e.g. 3.f */);script.setInput(input);script.forEach(output);output.copyTo(bitmap);return bitmap;}// 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 = sentBitmap.copy(sentBitmap.getConfig(), true);if (radius < 1) {return (null);}int w = bitmap.getWidth();int h = bitmap.getHeight();int[] pix = new int[w * h];Log.e("pix", w + " " + h + " " + pix.length);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;}}Log.e("pix", w + " " + h + " " + pix.length);bitmap.setPixels(pix, 0, w, 0, 0, w, h);return (bitmap);}}

参考：

https://github.com/PomepuyN/BlurEffectForAndroidDesign