自定义imageView圆形图片

package com.pan.util;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.ImageView;
/**
 * 自定义圆形 ImageView
 * @author 钟买能
 * @version 1.0
 * @since 2014-5-30
 */
public class RoundImageView extends ImageView {
    
    public RoundImageView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
    }

    public RoundImageView(Context context, AttributeSet attrs) {
        super(context, attrs);

    }

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

    }

    @Override
    protected void onDraw(Canvas canvas) {
        
        // 获取当前控件的 drawable
        Drawable drawable = getDrawable();

        if (drawable == null) {
            return;
        }

        // 这里 get 回来的宽度和高度是当前控件相对应的宽度和高度（在 xml 设置）
        if (getWidth() == 0 || getHeight() == 0) {
            return; 
        }
    
        // 画笔
        Paint paint = new Paint();
        // 颜色设置
        paint.setColor(0xff424242);
        // 抗锯齿
        paint.setAntiAlias(true);
        //Paint 的 Xfermode，PorterDuff.Mode.SRC_IN 取两层图像的交集部门, 只显示上层图像。 
        PorterDuffXfermode xfermode = new PorterDuffXfermode(PorterDuff.Mode.SRC_IN);
        // 获取 bitmap，即传入 imageview 的 bitmap
        Bitmap bitmap =  ((BitmapDrawable)drawable).getBitmap() ;

        // 标志
        int saveFlags = Canvas.MATRIX_SAVE_FLAG | Canvas.CLIP_SAVE_FLAG | Canvas.HAS_ALPHA_LAYER_SAVE_FLAG | Canvas.FULL_COLOR_LAYER_SAVE_FLAG | Canvas.CLIP_TO_LAYER_SAVE_FLAG;
        canvas.saveLayer(0, 0, getWidth(), getHeight(), null, saveFlags);
        
        // 画遮罩，画出来就是一个和空间大小相匹配的圆
        canvas.drawCircle(getWidth()/2, getHeight()/2, getWidth()/2, paint);
        paint.setXfermode(xfermode);
        
        // 空间的大小 /bitmap 的大小 =bitmap 缩放的倍数
        float scaleWidth = ((float) getWidth()) / bitmap.getWidth();
        float scaleHeight = ((float) getHeight()) / bitmap.getHeight();
        
        Matrix matrix = new Matrix();
        matrix.postScale(scaleWidth, scaleHeight); 
        
        //bitmap 缩放
        bitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
        
        //draw 上去
        canvas.drawBitmap(bitmap, 0, 0, paint);
//        paint.setXfermode(null);
        canvas.restore();

    }

}