圆形imageview

public static Bitmap toRoundCorner(Bitmap bitmap, float pixels) {  
        System.out.println("图片是否变成圆角模式了+++++++++++++");
        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), 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(Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, paint);  
        System.out.println("pixels+++++++"+pixels);
        return output;  
    }