glide加载圆角图片

附录1简单介绍了Android开源的图片加载框架。在实际的开发中，虽然Glide解决了快速加载图片的问题，但还有一个问题悬而未决：比如用户的头像，往往用户的头像是从服务器端读出的一个普通矩形图片，但是现在的设计一般要求在APP端的用户头像显示成圆形头像，那么此时虽然Glide可以加载，但加载出来的是一个矩形，如果要Glide在加载过程中就把矩形图转换成圆形的，则需要在Glide之上引入一个开源项目：glide-transformations
glide-transformations在github上的项目主页是： https://github.com/wasabeef/glide-transformations  

写一个例子说明。

package zhangphil.app;  
  
import android.support.v7.app.AppCompatActivity;  
import android.os.Bundle;  
import android.widget.ImageView;  
  
import com.bumptech.glide.Glide;  
  
import jp.wasabeef.glide.transformations.BlurTransformation;  
import jp.wasabeef.glide.transformations.CropCircleTransformation;  
import jp.wasabeef.glide.transformations.RoundedCornersTransformation;  
  
public class MainActivity extends AppCompatActivity {  
  
    //我csdn博客头像  
    String url = "http://avatar.csdn.net/9/7/A/1_zhangphil.jpg";  
  
    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
  
        //原图，是我博客的头像  
        ImageView image1 = (ImageView) findViewById(R.id.image1);  
        Glide.with(this).load(url).crossFade(1000).into(image1);  
  
        //原图 -> 圆图  
        ImageView image2 = (ImageView) findViewById(R.id.image2);  
        Glide.with(this).load(url).bitmapTransform(new CropCircleTransformation(this)).crossFade(1000).into(image2);  
  
        //原图的毛玻璃、高斯模糊效果  
        ImageView image3 = (ImageView) findViewById(R.id.image3);  
        Glide.with(this).load(url).bitmapTransform(new BlurTransformation(this, 25)).crossFade(1000).into(image3);  
  
        //原图基础上复合变换成圆图 +毛玻璃（高斯模糊）  
        ImageView image4 = (ImageView) findViewById(R.id.image4);  
        Glide.with(this).load(url).bitmapTransform(new BlurTransformation(this, 25), new CropCircleTransformation(this)).crossFade(1000).into(image4);  
  
        //原图处理成圆角，如果是四周都是圆角则是RoundedCornersTransformation.CornerType.ALL  
        ImageView image5 = (ImageView) findViewById(R.id.image5);  
        Glide.with(this).load(url).bitmapTransform(new RoundedCornersTransformation(this, 30, 0, RoundedCornersTransformation.CornerType.BOTTOM)).crossFade(1000).into(image5);  
    }  
}  

主要实现类如下是所示，可以加载圆形图像，椭圆图像，以及矩形圆角，上圆角，下圆角。

/**
 * Copyright (C) 2017 Wasabeef
 * 

 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 

 * http://www.apache.org/licenses/LICENSE-2.0
 * 

 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.Shader;

import com.bumptech.glide.Glide;
import com.bumptech.glide.load.Transformation;
import com.bumptech.glide.load.engine.Resource;
import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
import com.bumptech.glide.load.resource.bitmap.BitmapResource;

public class RoundedCornersTransformation implements Transformation {

    public enum CornerType {
        ALL,
        TOP_LEFT, TOP_RIGHT, BOTTOM_LEFT, BOTTOM_RIGHT,
        TOP, BOTTOM, LEFT, RIGHT,
        OTHER_TOP_LEFT, OTHER_TOP_RIGHT, OTHER_BOTTOM_LEFT, OTHER_BOTTOM_RIGHT,
        DIAGONAL_FROM_TOP_LEFT, DIAGONAL_FROM_TOP_RIGHT
    }

    private BitmapPool mBitmapPool;
    private int mRadius;
    private int mDiameter;
    private int mMargin;
    private CornerType mCornerType;

    public RoundedCornersTransformation(Context context, int radius, int margin) {
        this(context, radius, margin, CornerType.ALL);
    }

    public RoundedCornersTransformation(BitmapPool pool, int radius, int margin) {
        this(pool, radius, margin, CornerType.ALL);
    }

    public RoundedCornersTransformation(Context context, int radius, int margin,
                                        CornerType cornerType) {
        this(Glide.get(context).getBitmapPool(), radius, margin, cornerType);
    }

    public RoundedCornersTransformation(BitmapPool pool, int radius, int margin,
                                        CornerType cornerType) {
        mBitmapPool = pool;
        mRadius = radius;
        mDiameter = mRadius * 2;
        mMargin = margin;
        mCornerType = cornerType;
    }

    @Override
    public Resource transform(Resource resource, int outWidth, int outHeight) {
        Bitmap source = resource.get();

        int width = source.getWidth();
        int height = source.getHeight();

        Bitmap bitmap = mBitmapPool.get(width, height, Bitmap.Config.ARGB_8888);
        if (bitmap == null) {
            bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        }

        Canvas canvas = new Canvas(bitmap);
        Paint paint = new Paint();
        paint.setAntiAlias(true);
        paint.setShader(new BitmapShader(source, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP));
        drawRoundRect(canvas, paint, width, height);
        return BitmapResource.obtain(bitmap, mBitmapPool);
    }

    private void drawRoundRect(Canvas canvas, Paint paint, float width, float height) {
        float right = width - mMargin;
        float bottom = height - mMargin;

        switch (mCornerType) {
            case ALL:
                canvas.drawRoundRect(new RectF(mMargin, mMargin, right, bottom), mRadius, mRadius, paint);
                break;
            case TOP_LEFT:
                drawTopLeftRoundRect(canvas, paint, right, bottom);
                break;
            case TOP_RIGHT:
                drawTopRightRoundRect(canvas, paint, right, bottom);
                break;
            case BOTTOM_LEFT:
                drawBottomLeftRoundRect(canvas, paint, right, bottom);
                break;
            case BOTTOM_RIGHT:
                drawBottomRightRoundRect(canvas, paint, right, bottom);
                break;
            case TOP:
                drawTopRoundRect(canvas, paint, right, bottom);
                break;
            case BOTTOM:
                drawBottomRoundRect(canvas, paint, right, bottom);
                break;
            case LEFT:
                drawLeftRoundRect(canvas, paint, right, bottom);
                break;
            case RIGHT:
                drawRightRoundRect(canvas, paint, right, bottom);
                break;
            case OTHER_TOP_LEFT:
                drawOtherTopLeftRoundRect(canvas, paint, right, bottom);
                break;
            case OTHER_TOP_RIGHT:
                drawOtherTopRightRoundRect(canvas, paint, right, bottom);
                break;
            case OTHER_BOTTOM_LEFT:
                drawOtherBottomLeftRoundRect(canvas, paint, right, bottom);
                break;
            case OTHER_BOTTOM_RIGHT:
                drawOtherBottomRightRoundRect(canvas, paint, right, bottom);
                break;
            case DIAGONAL_FROM_TOP_LEFT:
                drawDiagonalFromTopLeftRoundRect(canvas, paint, right, bottom);
                break;
            case DIAGONAL_FROM_TOP_RIGHT:
                drawDiagonalFromTopRightRoundRect(canvas, paint, right, bottom);
                break;
            default:
                canvas.drawRoundRect(new RectF(mMargin, mMargin, right, bottom), mRadius, mRadius, paint);
                break;
        }
    }

    private void drawTopLeftRoundRect(Canvas canvas, Paint paint, float right, float bottom) {
        canvas.drawRoundRect(new RectF(mMargin, mMargin, mMargin + mDiameter, mMargin + mDiameter),
                mRadius, mRadius, paint);
        canvas.drawRect(new RectF(mMargin, mMargin + mRadius, mMargin + mRadius, bottom), paint);
        canvas.drawRect(new RectF(mMargin + mRadius, mMargin, right, bottom), paint);
    }

    private void drawTopRightRoundRect(Canvas canvas, Paint paint, float right, float bottom) {
        canvas.drawRoundRect(new RectF(right - mDiameter, mMargin, right, mMargin + mDiameter), mRadius,
                mRadius, paint);
        canvas.drawRect(new RectF(mMargin, mMargin, right - mRadius, bottom), paint);
        canvas.drawRect(new RectF(right - mRadius, mMargin + mRadius, right, bottom), paint);
    }

    private void drawBottomLeftRoundRect(Canvas canvas, Paint paint, float right, float bottom) {
        canvas.drawRoundRect(new RectF(mMargin, bottom - mDiameter, mMargin + mDiameter, bottom),
                mRadius, mRadius, paint);
        canvas.drawRect(new RectF(mMargin, mMargin, mMargin + mDiameter, bottom - mRadius), paint);
        canvas.drawRect(new RectF(mMargin + mRadius, mMargin, right, bottom), paint);
    }

    private void drawBottomRightRoundRect(Canvas canvas, Paint paint, float right, float bottom) {
        canvas.drawRoundRect(new RectF(right - mDiameter, bottom - mDiameter, right, bottom), mRadius,
                mRadius, paint);
        canvas.drawRect(new RectF(mMargin, mMargin, right - mRadius, bottom), paint);
        canvas.drawRect(new RectF(right - mRadius, mMargin, right, bottom - mRadius), paint);
    }

    private void drawTopRoundRect(Canvas canvas, Paint paint, float right, float bottom) {
        canvas.drawRoundRect(new RectF(mMargin, mMargin, right, mMargin + mDiameter), mRadius, mRadius,
                paint);
        canvas.drawRect(new RectF(mMargin, mMargin + mRadius, right, bottom), paint);
    }

    private void drawBottomRoundRect(Canvas canvas, Paint paint, float right, float bottom) {
        canvas.drawRoundRect(new RectF(mMargin, bottom - mDiameter, right, bottom), mRadius, mRadius,
                paint);
        canvas.drawRect(new RectF(mMargin, mMargin, right, bottom - mRadius), paint);
    }

    private void drawLeftRoundRect(Canvas canvas, Paint paint, float right, float bottom) {
        canvas.drawRoundRect(new RectF(mMargin, mMargin, mMargin + mDiameter, bottom), mRadius, mRadius,
                paint);
        canvas.drawRect(new RectF(mMargin + mRadius, mMargin, right, bottom), paint);
    }

    private void drawRightRoundRect(Canvas canvas, Paint paint, float right, float bottom) {
        canvas.drawRoundRect(new RectF(right - mDiameter, mMargin, right, bottom), mRadius, mRadius,
                paint);
        canvas.drawRect(new RectF(mMargin, mMargin, right - mRadius, bottom), paint);
    }

    private void drawOtherTopLeftRoundRect(Canvas canvas, Paint paint, float right, float bottom) {
        canvas.drawRoundRect(new RectF(mMargin, bottom - mDiameter, right, bottom), mRadius, mRadius,
                paint);
        canvas.drawRoundRect(new RectF(right - mDiameter, mMargin, right, bottom), mRadius, mRadius,
                paint);
        canvas.drawRect(new RectF(mMargin, mMargin, right - mRadius, bottom - mRadius), paint);
    }

    private void drawOtherTopRightRoundRect(Canvas canvas, Paint paint, float right, float bottom) {
        canvas.drawRoundRect(new RectF(mMargin, mMargin, mMargin + mDiameter, bottom), mRadius, mRadius,
                paint);
        canvas.drawRoundRect(new RectF(mMargin, bottom - mDiameter, right, bottom), mRadius, mRadius,
                paint);
        canvas.drawRect(new RectF(mMargin + mRadius, mMargin, right, bottom - mRadius), paint);
    }

    private void drawOtherBottomLeftRoundRect(Canvas canvas, Paint paint, float right, float bottom) {
        canvas.drawRoundRect(new RectF(mMargin, mMargin, right, mMargin + mDiameter), mRadius, mRadius,
                paint);
        canvas.drawRoundRect(new RectF(right - mDiameter, mMargin, right, bottom), mRadius, mRadius,
                paint);
        canvas.drawRect(new RectF(mMargin, mMargin + mRadius, right - mRadius, bottom), paint);
    }

    private void drawOtherBottomRightRoundRect(Canvas canvas, Paint paint, float right,
                                               float bottom) {
        canvas.drawRoundRect(new RectF(mMargin, mMargin, right, mMargin + mDiameter), mRadius, mRadius,
                paint);
        canvas.drawRoundRect(new RectF(mMargin, mMargin, mMargin + mDiameter, bottom), mRadius, mRadius,
                paint);
        canvas.drawRect(new RectF(mMargin + mRadius, mMargin + mRadius, right, bottom), paint);
    }

    private void drawDiagonalFromTopLeftRoundRect(Canvas canvas, Paint paint, float right,
                                                  float bottom) {
        canvas.drawRoundRect(new RectF(mMargin, mMargin, mMargin + mDiameter, mMargin + mDiameter),
                mRadius, mRadius, paint);
        canvas.drawRoundRect(new RectF(right - mDiameter, bottom - mDiameter, right, bottom), mRadius,
                mRadius, paint);
        canvas.drawRect(new RectF(mMargin, mMargin + mRadius, right - mDiameter, bottom), paint);
        canvas.drawRect(new RectF(mMargin + mDiameter, mMargin, right, bottom - mRadius), paint);
    }

    private void drawDiagonalFromTopRightRoundRect(Canvas canvas, Paint paint, float right,
                                                   float bottom) {
        canvas.drawRoundRect(new RectF(right - mDiameter, mMargin, right, mMargin + mDiameter), mRadius,
                mRadius, paint);
        canvas.drawRoundRect(new RectF(mMargin, bottom - mDiameter, mMargin + mDiameter, bottom),
                mRadius, mRadius, paint);
        canvas.drawRect(new RectF(mMargin, mMargin, right - mRadius, bottom - mRadius), paint);
        canvas.drawRect(new RectF(mMargin + mRadius, mMargin + mRadius, right, bottom), paint);
    }

    @Override
    public String getId() {
        return "RoundedTransformation(radius=" + mRadius + ", margin=" + mMargin + ", diameter="
                + mDiameter + ", cornerType=" + mCornerType.name() + ")";
    }
}

如有疑问，大家共勉