Android学习笔记之详细讲解画圆角图片

package xiaosi.RoundConcer;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.RectF;
import android.os.Bundle;
import android.widget.ImageView;

public class RoundConcerActivity extends Activity
{
    /** Called when the activity is first created. */
    private ImageView roundImage = null;
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        roundImage = (ImageView)findViewById(R.id.roundconcer);


        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.a);
        roundImage.setImageBitmap(getRoundCornerImage(bitmap, 50));
    }

    public static Bitmap getRoundCornerImage(Bitmap bitmap, int roundPixels)
    {
        //创建一个和原始图片一样大小位图
        Bitmap roundConcerImage = Bitmap.createBitmap(bitmap.getWidth(),
                bitmap.getHeight(), Config.ARGB_8888);
        //创建带有位图roundConcerImage的画布
        Canvas canvas = new Canvas(roundConcerImage);
        //创建画笔
        Paint paint = new Paint();
        //创建一个和原始图片一样大小的矩形
        Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
        RectF rectF = new RectF(rect);
        // 去锯齿
        paint.setAntiAlias(true);
        //画一个和原始图片一样大小的圆角矩形
        canvas.drawRoundRect(rectF, roundPixels, roundPixels, paint);
        //设置相交模式
        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
        //把图片画到矩形去
        canvas.drawBitmap(bitmap, null, rect, paint);
        return roundConcerImage;
    }
}