android 圆角图片的实现

public class ToRoundCorner extends Activity{

    public Bitmap toRoundCorner(Bitmap bitmap, int pixels) {

        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);
        final int color = 0xff424242;
        final Paint paint = new Paint();
        final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
        final RectF rectF = new RectF(rect);
        final float roundPx = pixels;
        paint.setAntiAlias(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(color);
        canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, paint);
        return output;
    }

}

ImageView pic = (ImageView) navigationView.getHeaderView(0).findViewById(R.id.tou_pic);
        TextView username = (TextView) navigationView.getHeaderView(0).findViewById(R.id.nav_username);
        TextView phone = (TextView) navigationView.getHeaderView(0).findViewById(R.id.nav_phone);

        //将图片转换成bitmap
        Drawable drawable = getResources().getDrawable(R.mipmap.aboutus);
        BitmapDrawable bitmapDrawable = (BitmapDrawable) drawable;
        Bitmap bitmap = bitmapDrawable.getBitmap();
        //将图片转成圆角
        ToRoundCorner toround = new ToRoundCorner();
        pic.setImageBitmap(toround.toRoundCorner(bitmap , 50));