需求: 用 ImageView 显示一寸照为圆形头像

问题: 默认显示的是中间部分的正方形区域, 头发被遮挡;

解决: 用户上传的头像无非三种情况: 正方形, 纵向长图, 横向长图;

1. 正方形: 直接显示;
2. 纵向长图: 显示最上面的正方形区域;
3. 横向长图: 显示中间区域的正方形区域;

下面给出思路图:

思路图

使用

布局: 
<ImageView
    android:id="@+id/ivAvatar"
    android:layout_width="80dp"
    android:layout_height="80dp" />

java代码:
ImageView ivAvatar= (ImageView) findViewById(R.id.ivAvatar);
//头像
Glide.with(mContext)
    .load(iconUrl)
    .dontAnimate()
    .placeholder(R.mipmap.my_xinxi)
    .error(R.mipmap.my_xinxi)
    .diskCacheStrategy(DiskCacheStrategy.RESULT)
    .transform(new CircleAvatarTransform(mContext))
    .into(ivAvatar);

CircleAvatarTransform.java源码

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;

import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
import com.bumptech.glide.load.resource.bitmap.BitmapTransformation;

/**
 * 从一寸照中截取出圆形头像, 不遮挡头发和脸蛋的那种
 *
 * 纵向长图: 取最上面的正方形
 * 横向长图: 取中间正方形
 * 正方形: 不处理
 * <p>
 * 作者: geaosu
 */
public class CircleAvatarTransform extends BitmapTransformation {
    public CircleAvatarTransform(Context context) {
        super(context);
    }

    @Override
    protected Bitmap transform(BitmapPool pool, Bitmap toTransform, int outWidth, int outHeight) {
        return circleCrop(pool, toTransform);
    }

    private Bitmap circleCrop(BitmapPool pool, Bitmap source) {
        int w = source.getWidth();
        int h = source.getHeight();
        Bitmap bitmapTemp = null;
        if (w < h) {
            //纵向长图: 要处理
            int widthTemp = w >= h ? h : w;
            int heightTemp = widthTemp;
            int x = 0;
            int y = 30;
            if (y + heightTemp > h) {
                y = 0;
            }
            //截取bitmap
            bitmapTemp = Bitmap.createBitmap(source, x, y, widthTemp, heightTemp, null, false);
        } else {
            //横向长图, 正方形: 不处理
            bitmapTemp = source;
        }

        int size = Math.min(bitmapTemp.getWidth(), bitmapTemp.getHeight());

        int width = (bitmapTemp.getWidth() - size) / 2;
        int height = (bitmapTemp.getHeight() - size) / 2;

        Bitmap bitmap = pool.get(size, size, Bitmap.Config.ARGB_8888);
        if (bitmap == null) {
            bitmap = Bitmap.createBitmap(size, size, Bitmap.Config.ARGB_8888);
        }

        Canvas canvas = new Canvas(bitmap);
        Paint paint = new Paint();
        BitmapShader shader = new BitmapShader(bitmapTemp, BitmapShader.TileMode.CLAMP, BitmapShader.TileMode.CLAMP);
        if (width != 0 || height != 0) {
            // source isn't square, move viewport to center
            Matrix matrix = new Matrix();
            matrix.setTranslate(-width, -height);
            shader.setLocalMatrix(matrix);
        }
        paint.setShader(shader);
        paint.setAntiAlias(true);

        float r = size / 2f;
        canvas.drawCircle(r, r, r, paint);

        return bitmap;
    }

    @Override
    public String getId() {
        return getClass().getName();
    }


}