1. 将原图居中裁剪成正方形
2. 依据指定的宽度对正方形进行缩放
3. 裁剪成圆形

效果

package com.demos.tencent_qq_ui.CustomerView;

import android.content.Context; 
import android.graphics.Bitmap; 
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet; 
import android.widget.ImageView;
 

/**
 * Created by mummyding on 15-8-7.
 */
public class AvatarImageView extends ImageView {
    private Paint paint = new Paint();

    public AvatarImageView(Context context) {
        super(context);
    }

    public AvatarImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public AvatarImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    //将头像按比例缩放
    private Bitmap scaleBitmap(Bitmap bitmap){
        int width = getWidth();
        //一定要强转成float 不然有可能由于精度不够 出现 scale为0 的错误
        float scale = (float)width/(float)bitmap.getWidth();
        Matrix matrix = new Matrix();
        matrix.postScale(scale, scale);
        return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);

    }
    //将原始图像裁剪成正方形
    private Bitmap dealRawBitmap(Bitmap bitmap){
        int width = bitmap.getWidth();
        int height = bitmap.getHeight();
        //获取宽度
        int minWidth = width > height ?
  height:width ;
        //计算正方形的范围
        int leftTopX = (width - minWidth)/2;
        int leftTopY = (height - minWidth)/2;
        //裁剪成正方形
        Bitmap newBitmap = Bitmap.createBitmap(bitmap,leftTopX,leftTopY,minWidth,minWidth,null,false);
        return  scaleBitmap(newBitmap);
    }
    @Override
    protected void onDraw(Canvas canvas) {
        Drawable drawable = getDrawable();
        if (null != drawable) {
            Bitmap rawBitmap =((BitmapDrawable)drawable).getBitmap();

            //处理Bitmap 转成正方形
            Bitmap newBitmap = dealRawBitmap(rawBitmap);
            //将newBitmap 转换成圆形
            Bitmap circleBitmap = toRoundCorner(newBitmap, 14);

            final Rect rect = new Rect(0, 0, circleBitmap.getWidth(), circleBitmap.getHeight());
            paint.reset();
            //绘制到画布上
            canvas.drawBitmap(circleBitmap, rect, rect, paint);
        } else {
            super.onDraw(canvas);
        }
    }

    private Bitmap toRoundCorner(Bitmap bitmap, int pixels) {

        //指定为 ARGB_4444 能够减小图片大小
        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.ARGB_4444);
        Canvas canvas = new Canvas(output);

        final int color = 0xff424242;
        final Rect rect = new Rect(0, 0,bitmap.getWidth(), bitmap.getHeight());
        paint.setAntiAlias(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(color);
        int x = bitmap.getWidth();
        canvas.drawCircle(x / 2, x / 2, x / 2, paint);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, paint);
        return output;
    }
}

 <com.demos.tencent_qq_ui.CustomerView.AvatarImageView
       android:layout_width="96dip"  <!--可自行指定大小-->
       android:layout_height="96dip"
       android:layout_centerHorizontal="true"
       android:src=http://www.mamicode.com/"@drawable/avatar"  >

这样,在界面上显示的图像就是圆形的了.

【转载请注明出处】

Author: MummyDing

出处:http://blog.csdn.net/u012560612/article/category/5651761