android 高斯模糊实现
高斯模糊
高斯模糊就是将指定像素变换为其与周边像素加权平均后的值,权重就是高斯分布函数计算出来的值。
一种实现
点击打开链接<-这里是一片关于高斯模糊算法的介绍,我们需要首先根据高斯分布函数计算权重值,为了提高效率我们采用一维高斯分布函数,然后处理图像的时候在横向和纵向进行两次计算得到结果。下面是一种实现
- public static void gaussBlur(int[] data, int width, int height, int radius,
- float sigma) {
- float pa = (float) (1 / (Math.sqrt(2 * Math.PI) * sigma));
- float pb = -1.0f / (2 * sigma * sigma);
- // generate the Gauss Matrix
- float[] gaussMatrix = new float[radius * 2 + 1];
- float gaussSum = 0f;
- for (int i = 0, x = -radius; x <= radius; ++x, ++i) {
- float g = (float) (pa * Math.exp(pb * x * x));
- gaussMatrix[i] = g;
- gaussSum += g;
- }
- for (int i = 0, length = gaussMatrix.length; i < length; ++i) {
- gaussMatrix[i] /= gaussSum;
- }
- // x direction
- for (int y = 0; y < height; ++y) {
- for (int x = 0; x < width; ++x) {
- float r = 0, g = 0, b = 0;
- gaussSum = 0;
- for (int j = -radius; j <= radius; ++j) {
- int k = x + j;
- if (k >= 0 && k < width) {
- int index = y * width + k;
- int color = data[index];
- int cr = (color & 0x00ff0000) >> 16;
- int cg = (color & 0x0000ff00) >> 8;
- int cb = (color & 0x000000ff);
- r += cr * gaussMatrix[j + radius];
- g += cg * gaussMatrix[j + radius];
- b += cb * gaussMatrix[j + radius];
- gaussSum += gaussMatrix[j + radius];
- }
- }
- int index = y * width + x;
- int cr = (int) (r / gaussSum);
- int cg = (int) (g / gaussSum);
- int cb = (int) (b / gaussSum);
- data[index] = cr << 16 | cg << 8 | cb | 0xff000000;
- }
- }
- // y direction
- for (int x = 0; x < width; ++x) {
- for (int y = 0; y < height; ++y) {
- float r = 0, g = 0, b = 0;
- gaussSum = 0;
- for (int j = -radius; j <= radius; ++j) {
- int k = y + j;
- if (k >= 0 && k < height) {
- int index = k * width + x;
- int color = data[index];
- int cr = (color & 0x00ff0000) >> 16;
- int cg = (color & 0x0000ff00) >> 8;
- int cb = (color & 0x000000ff);
- r += cr * gaussMatrix[j + radius];
- g += cg * gaussMatrix[j + radius];
- b += cb * gaussMatrix[j + radius];
- gaussSum += gaussMatrix[j + radius];
- }
- }
- int index = y * width + x;
- int cr = (int) (r / gaussSum);
- int cg = (int) (g / gaussSum);
- int cb = (int) (b / gaussSum);
- data[index] = cr << 16 | cg << 8 | cb | 0xff000000;
- }
- }
- }
实际测试会发现这种计算方式是很耗时间的,而且模糊半径越大,从原理也可以看到计算量是平方增长的,所以计算时间也越长。
RenderScript
RenderScript是Android在API 11之后加入的,用于高效的图片处理,包括模糊、混合、矩阵卷积计算等,代码示例如下
- public Bitmap blurBitmap(Bitmap bitmap){
- //Let's create an empty bitmap with the same size of the bitmap we want to blur
- Bitmap outBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Config.ARGB_8888);
- //Instantiate a new Renderscript
- RenderScript rs = RenderScript.create(getApplicationContext());
- //Create an Intrinsic Blur Script using the Renderscript
- ScriptIntrinsicBlur blurScript = ScriptIntrinsicBlur.create(rs, Element.U8_4(rs));
- //Create the Allocations (in/out) with the Renderscript and the in/out bitmaps
- Allocation allIn = Allocation.createFromBitmap(rs, bitmap);
- Allocation allOut = Allocation.createFromBitmap(rs, outBitmap);
- //Set the radius of the blur
- blurScript.setRadius(25.f);
- //Perform the Renderscript
- blurScript.setInput(allIn);
- blurScript.forEach(allOut);
- //Copy the final bitmap created by the out Allocation to the outBitmap
- allOut.copyTo(outBitmap);
- //recycle the original bitmap
- bitmap.recycle();
- //After finishing everything, we destroy the Renderscript.
- rs.destroy();
- return outBitmap;
- }
(示例来源 https://gist.github.com/Mariuxtheone/903c35b4927c0df18cf8)
FastBlur
- 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 <mario@quasimondo.com>
- 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);
- }
这里的方法也可以实现高斯模糊的效果,但使用了特殊的算法,比第一种可以快很多,但比起RenderScript还是慢一些
实现YAHOO天气的动态模糊效果
YAHOO天气中的背景会随着手指上滑模糊程度加深,实际使用中发现怎么都达不到那样流畅的效果,因为手势刷新的速度很快,每一帧都去重新模糊计算一遍,还是会有延迟,造成页面卡顿。后来在一次偶然的开发中发现其实不需要每一帧都重新去模糊一遍,而是将图片最大程度模糊一次,之后和原图叠加,通过改变叠加的模糊图片的alpha值来达到不同程度的模糊效果。下面是一个例子,可以看到随着模糊图片alpha值的变化,叠加后产生不同程度的模糊效果。
随滑动变换alpha值的代码如下
- mBlurImage.setOnTouchListener(new OnTouchListener() {
- private float mLastY;
- @Override
- public boolean onTouch(View v, MotionEvent event) {
- switch (event.getAction()) {
- case MotionEvent.ACTION_DOWN:
- mLastY = event.getY();
- break;
- case MotionEvent.ACTION_MOVE:
- float y = event.getY();
- float alphaDelt = (y - mLastY) / 1000;
- float alpha = mBlurImage.getAlpha() + alphaDelt;
- if (alpha > 1.0) {
- alpha = 1.0f;
- } else if (alpha < 0.0) {
- alpha = 0.0f;
- }
- mTextView.setText(String.valueOf(alpha));
- mBlurImage.setAlpha(alpha);
- break;
- case MotionEvent.ACTION_UP:
- break;
- }
- return true;
- }
- });
示例代码下载 http://download.csdn.net/detail/xu_fu/7628139
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