Android Bitmap圆角

public Bitmap transform(Bitmap source) {
int size = Math.min(source.getWidth(), source.getHeight());

int x = (source.getWidth() - size) / 2;
int y = (source.getHeight() - size) / 2;

Bitmap squaredBitmap = Bitmap.createBitmap(source, x, y, size, size);
if (squaredBitmap != source) {
source.recycle();
}

Bitmap bitmap = Bitmap.createBitmap(size, size, source.getConfig());

Canvas canvas = new Canvas(bitmap);
Paint paint = new Paint();
BitmapShader shader = new BitmapShader(squaredBitmap, BitmapShader.TileMode.CLAMP, BitmapShader.TileMode.CLAMP);
paint.setShader(shader);
paint.setAntiAlias(true);

float r = size/2f;
canvas.drawCircle(r, r, r, paint);

squaredBitmap.recycle();
return bitmap;
}