此篇是我圆形图片学习总结的文章，最终实现的效果图如下

文章参考

Android圆形图片不求人，自定义View实现（BitmapShader使用）
Android - 实现图片圆角显示的几种方式
Android 完美实现图片圆角和圆形（对实现进行分析）

result.png

z.jpg

核心代码

class LoadTask1 extends AsyncTask<Void, Void, Bitmap> {

        @Override
        protected Bitmap doInBackground(Void... params) {
            Paint paint = new Paint();
            paint.setAntiAlias(true);
            paint.setFilterBitmap(true);
            //这里是获取到原图
            Bitmap bitmapSource = BitmapFactory.decodeResource(getResources(), R.drawable.z);
            //我通过getWidth，getHeight获取到了宽高
            Bitmap result = Bitmap.createBitmap(bitmapSource.getWidth(), bitmapSource.getHeight(), Bitmap.Config.ARGB_8888);
            //创建一个画布
            Canvas canvas = new Canvas(result);
            //通过宽高比，获取到最小的那个值
            int min = 0;
            if (result.getWidth() > result.getHeight()){
                min = result.getHeight();
            }else if (result.getWidth() < result.getHeight()){
                min = result.getWidth();
            }else {
                min = result.getWidth();
            }
            canvas.drawCircle(min/2,min/2,min/2,paint);//先画一个圆
            paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));//表示我下一步要取交集的地方
            canvas.drawBitmap(bitmapSource, 0, 0, paint);//又画一个图，并且这个图是在圆形的上面，此时就是获取到交集的地方
            return result;
        }

        @Override
        protected void onPostExecute(Bitmap bitmap) {
            imageView.setImageBitmap(bitmap);
        }
    }

核心思想

首先是画了一个圆形图片通过canvas.drawCircle方法
PorterDuff.Mode.SRC_IN：指明了取交集的部分
canvas.drawBitmap：又创建一个图片，这个图片是在圆形图之上的，此时就会有交集部分了

全部代码

public class MainActivity extends AppCompatActivity {

    int imageSize, radius;

    ImageView imageView;
    ImageView imageView2;

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

        imageView = (ImageView) findViewById(R.id.image);
        imageView2 = (ImageView) findViewById(R.id.image2);

        imageSize = getResources().getDimensionPixelSize(R.dimen.image_size);
        radius = getResources().getDimensionPixelSize(R.dimen.radius);

        new LoadTask1().execute();
        new LoadTask2().execute();
    }

    class LoadTask1 extends AsyncTask<Void, Void, Bitmap> {

        @Override
        protected Bitmap doInBackground(Void... params) {
            Paint paint = new Paint();
            paint.setAntiAlias(true);
            paint.setFilterBitmap(true);
            //这里是获取到原图
            Bitmap bitmapSource = BitmapFactory.decodeResource(getResources(), R.drawable.z);
            //我通过getWidth，getHeight获取到了宽高
            Bitmap result = Bitmap.createBitmap(bitmapSource.getWidth(), bitmapSource.getHeight(), Bitmap.Config.ARGB_8888);
            //创建一个画布
            Canvas canvas = new Canvas(result);
            //通过宽高比，获取到最小的那个值
            int min = 0;
            if (result.getWidth() > result.getHeight()){
                min = result.getHeight();
            }else if (result.getWidth() < result.getHeight()){
                min = result.getWidth();
            }else {
                min = result.getWidth();
            }
            canvas.drawCircle(min/2,min/2,min/2,paint);//先画一个圆
            paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));//表示我下一步要取交集的地方
            canvas.drawBitmap(bitmapSource, 0, 0, paint);//又画一个图，并且这个图是在圆形的上面，此时就是获取到交集的地方
            return result;
        }

        @Override
        protected void onPostExecute(Bitmap bitmap) {
            imageView.setImageBitmap(bitmap);
        }
    }

    class LoadTask2 extends AsyncTask<Void, Void, Bitmap> {

        @Override
        protected Bitmap doInBackground(Void... params) {
            Bitmap result = Bitmap.createBitmap(imageSize, imageSize, Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(result);

            Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.an);

            final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
            final RectF rectF = new RectF(0, 0, imageSize, imageSize);

            Paint paint = new Paint();
            paint.setAntiAlias(true);
            paint.setFilterBitmap(true);


            Path path = new Path();
            path.addRoundRect(rectF, radius, radius, Path.Direction.CW);
            canvas.clipPath(path, Region.Op.INTERSECT);

            canvas.drawBitmap(bitmap, rect, rectF, paint);

            return result;
        }

        @Override
        protected void onPostExecute(Bitmap bitmap) {
            imageView2.setImageBitmap(bitmap);
        }
    }

}