Glide框架高斯模糊图片处理

转自：https://ligboy.org/?p=380

对于不需要看废话的请直接Show me the code

对于模糊处理，一般的解决方案有四种:

Java实现的算法处理；
NDK实现的算法处理；
RenderScript处理；
openGL处理；

这四种方案的性能考虑的话，一般来讲应该是： 1 < 3 ＜ 2 < 4 (2、3的性能非常接近)，不过当属RenderScript方式最为简便（很显然嘛，平台无关性）。

RenderScript是Android自SDK17提供的一套平台无关计算密集脚本，它使用C99语法脚本，可以实现高性能的计算，而其包含大量内联函数，其中就包括了我们今天用到的：ScriptIntrinsicBlur，这是一个高斯模糊处理内联函数，一般系统用来进行阴影的计算处理。

上面有提到RenderScript是自SDK17引入的，但是Android 团队为我们提供了RenderScript support library，而起在Gradle-base的项目中的引入也极其简单，仅需要在module build.gradle设置以下11、12两行即可：

android {compileSdkVersion 23buildToolsVersion "23.0.2"defaultConfig {applicationId "org.ligboy.backsound"minSdkVersion 15targetSdkVersion 23versionCode 1versionName "1.0"renderscriptTargetApi 20renderscriptSupportModeEnabled true}buildTypes {release {minifyEnabled falseproguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'}}
}

接下来简单说说 ScriptIntrinsicBlur，使用它虽然很方便，但是也是有弊端的，模糊radius不能超过25.0f，不过我们可以通过缩小原图抽样的方式变相的进行扩大半径。

Glide是一个优秀的图片加载缓存处理等一系列功能的框架，它优雅而且使用渐变，扩展也很容易，Glide就提供了自定义Transformation的方式进行扩展图片的处理

到了这里就是通过自定义Transformation的方式，详细的这里就不赘述了，感兴趣可以查看Glide官方文档：Transformation。需要特别提到的是，每个Transformation都有一个String getId()的回调，该ID用于在对处理后的图片进行缓存时的文件命名，这样当下次相同图片使用相同Transformation时，则无需任何实际处理，直接读取缓存文件，所以我们实现时的ID需要同时关联所有的调整参数，参数改变的ID也应该相应改变。下面就是我自定义的BlurTransformation

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffColorFilter;
import android.support.annotation.FloatRange;
import android.support.v8.renderscript.Allocation;
import android.support.v8.renderscript.Element;
import android.support.v8.renderscript.RenderScript;
import android.support.v8.renderscript.ScriptIntrinsicBlur;import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
import com.bumptech.glide.load.resource.bitmap.BitmapTransformation;
import com.bumptech.glide.request.target.Target;/*** Georgia Blur Transformation* <p>* @author Ligboy.Liu ligboy@gmail.com.*/
public class BlurTransformation extends BitmapTransformation {private static final String ID = "org.ligboy.glide.BlurTransformation";public static final float DEFAULT_RADIUS = 25.0f;public static final float MAX_RADIUS = 25.0f;private static final float DEFAULT_SAMPLING = 1.0f;private Context mContext;private float mSampling = DEFAULT_SAMPLING;private float mRadius;private int mColor;public static class Builder {private Context mContext;private float mRadius = DEFAULT_RADIUS;private int mColor = Color.TRANSPARENT;public Builder(Context mContext) {this.mContext = mContext;}public float getRadius() {return mRadius;}public Builder setRadius(float radius) {mRadius = radius;return this;}public int getColor() {return mColor;}public Builder setColor(int color) {mColor = color;return this;}public BlurTransformation build() {return new BlurTransformation(mContext, mRadius, mColor);}}/**** @param context Context* @param radius The blur's radius.* @param color The color filter for blurring.*/public BlurTransformation(Context context, @FloatRange(from = 0.0f) float radius, int color) {super(context);mContext = context;if (radius > MAX_RADIUS) {mSampling = radius / 25.0f;mRadius = MAX_RADIUS;} else {mRadius = radius;}mColor = color;}/**** @param context Context* @param radius The blur's radius.*/public BlurTransformation(Context context, @FloatRange(from = 0.0f) float radius) {this(context, radius, Color.TRANSPARENT);}public BlurTransformation(Context context) {this(context, DEFAULT_RADIUS);}/*** Transforms the given {@link Bitmap} based on the given dimensions and returns the transformed* result.* <p/>* <p>* The provided Bitmap, toTransform, should not be recycled or returned to the pool. Glide will automatically* recycle and/or reuse toTransform if the transformation returns a different Bitmap. Similarly implementations* should never recycle or return Bitmaps that are returned as the result of this method. Recycling or returning* the provided and/or the returned Bitmap to the pool will lead to a variety of runtime exceptions and drawing* errors. See #408 for an example. If the implementation obtains and discards intermediate Bitmaps, they may* safely be returned to the BitmapPool and/or recycled.* </p>* <p/>* <p>* outWidth and outHeight will never be {@link Target#SIZE_ORIGINAL}, this* class converts them to be the size of the Bitmap we're going to transform before calling this method.* </p>** @param pool        A {@link BitmapPool} that can be used to obtain and*                    return intermediate {@link Bitmap}s used in this transformation. For every*                    {@link Bitmap} obtained from the pool during this transformation, a*                    {@link Bitmap} must also be returned.* @param toTransform The {@link Bitmap} to transform.* @param outWidth    The ideal width of the transformed bitmap (the transformed width does not need to match exactly).* @param outHeight   The ideal height of the transformed bitmap (the transformed heightdoes not need to match*/@Overrideprotected Bitmap transform(BitmapPool pool, Bitmap toTransform, int outWidth, int outHeight) {boolean needScaled = mSampling == DEFAULT_SAMPLING;int originWidth = toTransform.getWidth();int originHeight = toTransform.getHeight();int width, height;if (needScaled) {width = originWidth;height = originHeight;} else {width = (int) (originWidth / mSampling);height = (int) (originHeight / mSampling);}//find a re-use bitmapBitmap bitmap = pool.get(width, height, Bitmap.Config.ARGB_8888);if (bitmap == null) {bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);}Canvas canvas = new Canvas(bitmap);if (mSampling != DEFAULT_SAMPLING) {canvas.scale(1 / mSampling, 1 / mSampling);}Paint paint = new Paint();paint.setFlags(Paint.FILTER_BITMAP_FLAG | Paint.ANTI_ALIAS_FLAG);PorterDuffColorFilter filter =new PorterDuffColorFilter(mColor, PorterDuff.Mode.SRC_ATOP);paint.setColorFilter(filter);canvas.drawBitmap(toTransform, 0, 0, paint);
// TIPS: Glide will take care of returning our original Bitmap to the BitmapPool for us,
// we needn't to recycle it.
//        toTransform.recycle();  <--- Just for tips. by LigboyRenderScript rs = RenderScript.create(mContext);Allocation input = Allocation.createFromBitmap(rs, bitmap, Allocation.MipmapControl.MIPMAP_NONE,Allocation.USAGE_SCRIPT);Allocation output = Allocation.createTyped(rs, input.getType());ScriptIntrinsicBlur blur = ScriptIntrinsicBlur.create(rs, Element.U8_4(rs));blur.setInput(input);blur.setRadius(mRadius);blur.forEach(output);output.copyTo(bitmap);rs.destroy();if (needScaled) {return bitmap;} else {Bitmap scaled = Bitmap.createScaledBitmap(bitmap, originWidth, originHeight, true);bitmap.recycle();return scaled;}}/*** A method to get a unique identifier for this particular transformation that can be used as part of a cache key.* The fully qualified class name for this class is appropriate if written out, but getClass().getName() is not* because the name may be changed by proguard.* <p/>* <p>* If this transformation does not affect the data that will be stored in cache, returning an empty string here* is acceptable.* </p>** @return A string that uniquely identifies this transformation.*/@Overridepublic String getId() {StringBuilder sb = new StringBuilder(ID);sb.append('-').append(mRadius).append('-').append(mColor);return sb.toString();}
}

使用起来也是非常简单：

Glide.with(MainActivity.this).load(imageFile.getUrl()).transform(new BlurTransformation(MainActivity.this, 100)).crossFade().into(mBackgroundImageView);

Gist: https://gist.github.com/ligboy/eee784aa57f40a615179

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