自定义圆形图片

package com.example.view;  
import android.content.Context;  
import android.graphics.Bitmap;  
import android.graphics.Bitmap.Config;  
import android.graphics.Canvas;  
import android.graphics.Paint;  
import android.graphics.PorterDuff.Mode;
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;

/**
 * 圆形ImageView，可设置最多两个宽度不同且颜色不同的圆形边框
 * 设置颜色在xml布局文件中由自定义属性配置参数指定
 */
public class MyView extends ImageView {
    private Context mContext;
    // 控件默认长、宽
    private int defaultWidth = 0;
    private int defaultHeight = 0;
    public MyView(Context context) {
        super(context);  
        mContext = context;
    }  
   
    public MyView(Context context, AttributeSet attrs) {  
        super(context, attrs);  
        mContext = context;  
    }  
   
    public MyView(Context context, AttributeSet attrs, int defStyle) {  
        super(context, attrs, defStyle);  
        mContext = context;  
    }
   
    @Override
    protected void onDraw(Canvas canvas) {  
        Drawable drawable = getDrawable() ;
        Bitmap b = ((BitmapDrawable) drawable).getBitmap();
        Bitmap bitmap = b.copy(Bitmap.Config.ARGB_8888, true);
        defaultWidth = getWidth();
        defaultHeight = getHeight();
        //如果defaultWidth 小于defaultHeight 成立，就返回defaultWidth ，否则就返回defaultHeight。
        int radius = (defaultWidth < defaultHeight ? defaultWidth : defaultHeight) / 2;
        Bitmap roundBitmap = getCroppedRoundBitmap(bitmap, radius);
        canvas.drawBitmap(roundBitmap, defaultWidth / 2 - radius, defaultHeight / 2 - radius, null);
    }
   
    /**  
     * 获取裁剪后的圆形图片  
     * @param radius半径  
     */
    public Bitmap getCroppedRoundBitmap(Bitmap bmp, int radius) {  
        Bitmap scaledSrcBmp;
        int diameter = radius * 2;
        // 为了防止宽高不相等，造成圆形图片变形，因此截取长方形中处于中间位置最大的正方形图片
        int squareWidth = 0, squareHeight = 0;
        int x = 0, y = 0;
        Bitmap squareBitmap;
        if (bmp.getHeight() > bmp.getWidth()) {
         // 高大于宽的时候，正方形的宽、高==图片的宽
            squareWidth = squareHeight = bmp.getWidth();
            x = 0;
            y = (bmp.getHeight() - bmp.getWidth()) / 2;
            // 截取正方形图片
            squareBitmap = Bitmap.createBitmap(bmp, x, y, squareWidth, squareHeight);
        } else if (bmp.getHeight() < bmp.getWidth()) {
         // 宽大于高的时候，正方形的宽、高==图片的高
            squareWidth = squareHeight = bmp.getHeight();
            x = (bmp.getWidth() - bmp.getHeight()) / 2;
            y = 0;
            // 截取正方形图片
            squareBitmap = Bitmap.createBitmap(bmp, x, y, squareWidth,squareHeight);
        } else {
         //宽等于高的时候，就直接取本图片
            squareBitmap = bmp;
        }
        if (squareBitmap.getWidth() != diameter || squareBitmap.getHeight() != diameter) {
         //如果正方形的宽、高不等于圆的直径，就将正方形图片进行缩放到和圆的直径相等的正方形
            scaledSrcBmp = Bitmap.createScaledBitmap(squareBitmap, diameter,diameter, true);
        } else {
            scaledSrcBmp = squareBitmap;
        }  
        //创建一个位图，等于正方形的宽、高
        Bitmap output = Bitmap.createBitmap(scaledSrcBmp.getWidth(),scaledSrcBmp.getHeight(),Config.ARGB_8888);  
        //创建一个画布
        Canvas canvas = new Canvas(output);
        //创建一个画笔
        Paint paint = new Paint();
        //创建一个正方形的矩阵
        Rect rect = new Rect(0, 0, scaledSrcBmp.getWidth(),scaledSrcBmp.getHeight());
        //设置画笔的锯齿效果
        paint.setAntiAlias(true);
        //绘制一个圆，
        canvas.drawCircle(scaledSrcBmp.getWidth() / 2,scaledSrcBmp.getHeight() / 2,scaledSrcBmp.getWidth() / 2,paint);
        //取绘制交集显示上层
        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
        //画一个位图，
        canvas.drawBitmap(scaledSrcBmp, rect, rect, paint);
        bmp = null;
        squareBitmap = null;
        scaledSrcBmp = null;
        return output;
    }  
}