将头图片变成圆形简单实现

package com.loaderman.customviewdemo;

import android.content.Context;
import android.graphics.*;
import android.util.AttributeSet;
import android.view.View;


public class AvatorView extends View {
    private Paint mPaint;
    private Bitmap mBitmap;
    private BitmapShader mBitmapShader;

    public AvatorView(Context context, AttributeSet attrs) throws Exception{
        super(context, attrs);
        mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.avator);
        mPaint = new Paint();
        mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Matrix matrix = new Matrix();
        float scale = (float) getWidth()/mBitmap.getWidth();
        matrix.setScale(scale,scale);
        mBitmapShader.setLocalMatrix(matrix);//设置坐标变换矩阵
        mPaint.setShader(mBitmapShader);

        float half = getWidth()/2;
        canvas.drawCircle(half,half,getWidth()/2,mPaint);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_gravity="center"
    android:gravity="center"
    android:background="@android:color/white"
    >


 <com.loaderman.customviewdemo.AvatorView
     android:layout_width="200dp"
     android:layout_height="200dp" />
</LinearLayout>