Android_绘制圆形图片

package com.example.demo_drawcircle;

import android.R.color;
import android.os.Bundle;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Bitmap.Config;
import android.view.Menu;
import android.view.ViewGroup.LayoutParams;
import android.widget.ImageView;
import android.widget.LinearLayout;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		LinearLayout layout = (LinearLayout) findViewById(R.id.main);
		LayoutParams lp = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
		
		
		Bitmap source = BitmapFactory.decodeResource(getResources(), R.drawable.icon);
		source = createCircleBitmap(source, 150);
		
		ImageView imageView = new ImageView(this);
		imageView.setImageBitmap(source);
		
		layout.addView(imageView,lp);
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}
	

	/**
	 * 
	 * @param source
	 * @param min
	 * @return
	 */
	private Bitmap createCircleBitmap(Bitmap source,int min){
		Paint paint = new Paint();
		paint.setColor(Color.parseColor("#FFFFFF"));
		paint.setAntiAlias(true);//抗锯齿
		
		Bitmap target = Bitmap.createBitmap(min, min, Config.ARGB_8888);
		/**
		 * 产生同样大小的画布
		 */
		Canvas canvas = new Canvas(target);
		
		/**
		 * 首先绘制圆形
		 */
		canvas.drawCircle(min/2, min/2, min/2, paint);
		/**
		 * 使用SRC_IN（关键代码）
		 */
		paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
		/**
		 * 缩放图片
		 */
		 //获取这个图片的宽和高
        int width = source.getWidth();
        int height = source.getHeight();
		//计算缩放率，新尺寸除原始尺寸
        float scaleWidth = ((float) min) / width;
        float scaleHeight = ((float) min) / height;
        
        // 创建操作图片用的matrix对象
        Matrix matrix = new Matrix();
        
        // 缩放图片动作
        matrix.postScale(scaleWidth, scaleHeight);
        
        //旋转图片 动作
//        matrix.postRotate(45);
        
        // 创建新的图片
        Bitmap newBitmap = Bitmap.createBitmap(source, 0, 0,
        width, height, matrix, true);
		/**
		 * 绘制图片
		 */		
		canvas.drawBitmap(newBitmap, 0, 0, paint);
		
		
		return target;
	}

}