Android RoundedBitmapDrawable：Android官方的圆角图形图象实现方案

RoundedBitmapDrawable是Android在support v4的扩展包中新增的实现圆角图形的关键类，借助RoundedBitmapDrawable的帮助，可以轻松的以Android标准方式实现圆角图形图象。
写一个简单的例子。
写一个线性布局，竖直方向放三个ImageView：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="zhangphil.app.MainActivity">

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="5dp" />

    <ImageView
        android:id="@+id/imageView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="5dp" />

    <ImageView
        android:id="@+id/imageView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="5dp" />

</LinearLayout>

然后通过Java代码分别放原始图，圆角图，圆形图作为对比：

package zhangphil.app;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.support.v4.graphics.drawable.RoundedBitmapDrawable;
import android.support.v4.graphics.drawable.RoundedBitmapDrawableFactory;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //未做圆角处理的原始图
        ImageView image1 = (ImageView) findViewById(R.id.imageView1);
        image1.setImageResource(R.drawable.zhangphil);

        //圆角图
        RoundedBitmapDrawable roundedDrawable = RoundedBitmapDrawableFactory.create(getResources(), BitmapFactory.decodeResource(getResources(), R.drawable.zhangphil));
        roundedDrawable.getPaint().setAntiAlias(true);
        roundedDrawable.setCornerRadius(30);
        ImageView image2 = (ImageView) findViewById(R.id.imageView2);
        image2.setImageDrawable(roundedDrawable);

        //圆形图
        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.zhangphil);
        RoundedBitmapDrawable circleDrawable = RoundedBitmapDrawableFactory.create(getResources(), BitmapFactory.decodeResource(getResources(), R.drawable.zhangphil));
        circleDrawable.getPaint().setAntiAlias(true);
        circleDrawable.setCornerRadius(Math.max(bitmap.getWidth(), bitmap.getHeight()));
        ImageView image3 = (ImageView) findViewById(R.id.imageView3);
        image3.setImageDrawable(circleDrawable);
    }
}

代码运行结果：

附录文章：
1，《Android圆形头像图Circle ImageView》链接地址：http://blog.csdn.net/zhangphil/article/details/44960551
2，《Android CustomShapeImageView对图片进行各种样式裁剪：圆形、星形、心形、花瓣形等》链接地址：http://blog.csdn.net/zhangphil/article/details/50119921