长文【Android模糊图片处理】
16lz
2021-01-24
现在许多app中都应用到了对图片的模糊处理，图片高斯模糊备受设计师的青睐，在各大知名APP中，如微信、手机QQ、网易云音乐等等都有对背景高斯图模糊的设计，还有今日头条、内涵段子等。
在Android 中，现在常用的图片高斯模糊技术的根本有两种：RenderScript 、fastBlur
1.RenderScript
RenderScript是在Android上的高性能运行密集型运算的框架。
是在Android3.0（API 11）引入的。而Android图片高斯模糊处理，通常也是用这个库来完成。它提供了我们Java层调用的API,实际上是在c/c++ 层来处理的，所以它的效率和性能通常是最高的。
缺点是：但是它只能在API 17或者更高的版本使用。当然也可以引用兼容包，但是会增加一点包的体积。并且模糊度有有限。
public class RSBlur { @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)private static Bitmap rsBlur(Context context,Bitmap source,int radius){ Bitmap inputBmp = source; //(1)初始化一个RenderScript Context：RenderScript 上下文环境通过create(Context)方法来创建，它保证RenderScript的使用并且提供一个控制后续所有RenderScript对象 RenderScript renderScript = RenderScript.create(context); //(2)通过Script至少创建一个Allocation：一个Allocation是提供存储大量可变数据的RenderScript 对象。 final Allocation input = Allocation.createFromBitmap(renderScript,inputBmp); final Allocation output = Allocation.createTyped(renderScript,input.getType()); //(3)创建ScriptIntrinsic：它内置了RenderScript 的一些通用操作，如高斯模糊、扭曲变换、图像混合等等 ScriptIntrinsicBlur scriptIntrinsicBlur = ScriptIntrinsicBlur.create(renderScript, Element.U8_4(renderScript)); //(4)填充数据到Allocations：除了使用方法createFromBitmap创建的Allocation外，其它的第一次创建时都是填充的空数据。 scriptIntrinsicBlur.setInput(input); //(5)设置模糊半径 (0---25) scriptIntrinsicBlur.setRadius(radius); //(6)启动内核，调用方法处理：调用forEach 方法模糊处理。 scriptIntrinsicBlur.forEach(output); //(7)从Allocation 中拷贝数据：为了能在Java层访问Allocation的数据，用Allocation其中一个copy方法来拷贝数据。 output.copyTo(inputBmp); //(8)销毁RenderScript对象 renderScript.destroy(); return inputBmp; }}2.fastBlur
fastBlur算法它直接在Java层做图片的模糊处理。对每个像素点应用高斯模糊计算、最后在合成Bitmap。就一个方法,使用这种方式不会有兼容性问题，也不会引入jar包导致APK变大。但是这种方法的效率是非常低的，想想也知道，因为是在Java 层处理，速度会更慢。将Bitmap全部加载到内存，较大图片容易OOM。
源码public class FastBlur { public static Bitmap blur(Bitmap sentBitmap, int radius, boolean canReuseInBitmap) { // Stack Blur v1.0 from // http://www.quasimondo.com/StackBlurForCanvas/StackBlurDemo.html // // Java Author: Mario Klingemann // http://incubator.quasimondo.com // created Feburary 29, 2004 // Android port : Yahel Bouaziz // 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 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); }} 使用中需要考虑的问题：
- sdk版本，如果是17或以下，就不能使用RenderScript
- 模糊前应该对源bitmap进行缩放,图片缩小后再进行模糊处理，需要处理的像素点和半径都变小，从而使得模糊处理速度加快。（缩小的系数应该为2的整数次幂 ，即上面代码中的scale应该为1/2、1/4、1/8 ... 参考BitmapFactory.Options 对图片缩放 的inSample系数）
两者结合使用
public Bitmap blurBitmap(Context context,Bitmap source,int radius){//缩放 int width = source.getWidth(); int height = source.getHeight(); int scaledWidth = width / 4; int scaledHeight = height / 4; Bitmap bitmap = Bitmap.createBitmap(scaledWidth, scaledHeight, Bitmap.Config.ARGB_8888); Canvas canvas = new Canvas(bitmap); canvas.scale(1.0F / (float)this.mSampling, 1.0F / (float)this.mSampling); Paint paint = new Paint(); paint.setFlags(2); canvas.drawBitmap(source, 0.0F, 0.0F, paint);//模糊处理 Bitmap newBitmap; if(Build.VERSION.SDK_INT >= 18) { newBitmap = RSBlur.blur(context, bitmap, radius)； } else { newBitmap = FastBlur.blur(bitmap,radius, true); } return newBitmap;}【分割线】
大量加载and优化
当我们的需求只有对一张图片进行模糊当做背景这种情况，直接进行上面所述的模糊就好，不需要做缓存等处理。
然而当我们要在列表中加载大量的模糊图片时（就像内涵段子首页视频展示），就要考虑优化，缓存，不应该过多重复的进行模糊。否则对造成滑动卡顿。
通常我们用Glide加载一张图片，在Glide基础上也有了一个开源库glide-transformations，可以进行模糊处理，并增加缓存，对模糊类也做了封装，方便使用。
一个小demo
compile 'jp.wasabeef:glide-transformations:2.0.1'
xml<?xml version="1.0" encoding="utf-8"?> public class MainActivity extends AppCompatActivity { private Context context; private ImageView iv_blur; private ImageView iv_origin; private String url ="http://mvimg2.meitudata.com/583bc2f76f58a6875.jpg"; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); context=this; setContentView(R.layout.activity_main); this.iv_blur = (ImageView) findViewById(R.id.iv_blur); this.iv_origin = (ImageView) findViewById(R.id.iv_origin); Glide.with(context).load(url) .bitmapTransform(new BlurTransformation(context, 23, 4)).into(new SimpleTarget() { @Override public void onResourceReady(final GlideDrawable glideDrawable, GlideAnimation<? super GlideDrawable> glideAnimation) { Glide.with(context).load(url) .asBitmap().into(new SimpleTarget() { @Override public void onResourceReady(Bitmap resource, GlideAnimation<? super Bitmap> glideAnimation) { //resource为原图 glideDrawable为模糊处理后得到的 //为了不改变原图的宽高，对原图resource进行等比例缩放 Matrix matrix = new Matrix(); float scale=resource.getHeight()/360 * context.getResources().getDisplayMetrics().density; matrix.postScale(scale, scale); Bitmap newResource=Bitmap.createBitmap(resource, 0, 0, resource.getWidth(), resource.getHeight(), matrix, true); iv_origin.setImageBitmap(resource); iv_blur.setImageDrawable(glideDrawable); } }); } }); }} 效果如下：
继续优化 可以看出我们进行了两次图片加载，一次用作背景模糊，一次用作原图显示，整体显得臃肿，还增加的请求的次数，所以我们可以重写自己的转换类，做我们自己的操作，把这两张图片进行合成。
如下：
public class MyBlurTransformation implements Transformation { private static int MAX_RADIUS = 25; private static int DEFAULT_DOWN_SAMPLING = 1; private Context mContext; private BitmapPool mBitmapPool; private int mRadius; private int mSampling; private int bitmapWidth; private int bitmapHeight; public MyBlurTransformation(Context context, BitmapPool pool, int radius, int sampling ,int bitmapWidth,int bitmapHeight){ this.mContext = context.getApplicationContext(); this.mBitmapPool = pool; this.mRadius = radius; this.mSampling = sampling; this.bitmapHeight=bitmapHeight; this.bitmapWidth=bitmapWidth; } public MyBlurTransformation(Context context, int radius, int sampling ,int bitmapWidth,int bitmapHeight) { this(context, Glide.get(context).getBitmapPool(), radius, sampling,bitmapWidth,bitmapHeight); } @Override public Resource transform(Resource resource, int outWidth, int outHeight) { //source为原图 glide 的url Bitmap source = (Bitmap)resource.get(); Bitmap composeBitmap= this.mBitmapPool.get(source.getWidth()/this.mSampling, source.getHeight()/this.mSampling, Bitmap.Config.ARGB_8888); if (composeBitmap==null){ composeBitmap= composeBitmap(source); } return BitmapResource.obtain(composeBitmap, this.mBitmapPool); } private Bitmap composeBitmap(Bitmap source) { int width = source.getWidth(); int height = source.getHeight(); int scaledWidth = width / this.mSampling; int scaledHeight = height / this.mSampling; Bitmap bitmap = this.mBitmapPool.get(scaledWidth, scaledHeight, Bitmap.Config.ARGB_8888); if(bitmap == null) { bitmap = Bitmap.createBitmap(scaledWidth, scaledHeight, Bitmap.Config.ARGB_8888); } Canvas canvas = new Canvas(bitmap); canvas.scale(1.0F / (float)this.mSampling, 1.0F / (float)this.mSampling); Paint paint = new Paint(); paint.setFlags(2); canvas.drawBitmap(source, 0.0F, 0.0F, paint); if(Build.VERSION.SDK_INT >= 18) { try { bitmap = RSBlur.blur(this.mContext, bitmap, this.mRadius); } catch (RSRuntimeException var13) { bitmap = FastBlur.blur(bitmap, this.mRadius, true); } } else { bitmap = FastBlur.blur(bitmap, this.mRadius, true); } Bitmap scaleGlideBitmap=scaleBlurBitmap(bitmap); Bitmap scaleResourceBitmap=scaleOriginBitmap(source); Bitmap newBitmap=Bitmap.createBitmap(bitmapWidth,bitmapHeight,scaleResourceBitmap.getConfig()); Canvas canvasnew=new Canvas(newBitmap); canvasnew.drawBitmap(scaleGlideBitmap,0,0,null); canvasnew.drawBitmap(scaleResourceBitmap,(bitmapWidth-scaleResourceBitmap.getWidth())/2,0,null); canvasnew.save(Canvas.ALL_SAVE_FLAG);//保存 canvasnew.restore();//存储 return newBitmap; } private Bitmap scaleOriginBitmap(Bitmap bkg) { int originHeight = bkg.getHeight(); float scaleWidth = ((float) bitmapHeight) / originHeight; Matrix matrix = new Matrix(); matrix.postScale(scaleWidth, scaleWidth); return Bitmap.createBitmap(bkg, 0, 0, bkg.getWidth(), bkg.getHeight(), matrix, true); } private Bitmap scaleBlurBitmap(Bitmap bitmap) { float scaleWidth=(float) bitmapWidth/bitmap.getWidth(); float scaleHeight=(float) bitmapHeight/bitmap.getHeight(); Matrix matrix = new Matrix(); matrix.postScale(scaleWidth, scaleHeight); return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true); } @Override public String getId() { return "BlurTransformation(radius=" + this.mRadius + ", sampling=" + this.mSampling + ")"; }} 然后MainActivity使用就可以如下这么写 （去掉iv_origin，用一张图显示）
传入 也就是imageview的宽高，用作对原图的缩放bitmapWidth =bitmapHeight= 自己获取 Glide.with(mContext).load(url).bitmapTransform(new MyBlurTransformation(mContext,23, 4,bitmapWidth,bitmapHeight)).into(new SimpleTarget(){ @Override public void onResourceReady(GlideDrawable resource, GlideAnimation<? super GlideDrawable> glideAnimation) { if (url.equals(vertical_view.getTag())) { blur_iv.setImageDrawable(resource); } } }); 以上例子只展示显示一张图，当然可以把它用在列表中，也已经做了缓存。
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