Android中显示圆形头像（读书笔记）

public static  Bitmap getCircleAvatar(Context context,Bitmap avatar){
Bitmap bitmap=Bitmap.createBitmap(avatar.getWidth(), avatar.getHeight(), Config.ARGB_8888);
Canvas canvas=new Canvas(bitmap);
Paint paint=new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(Color.BLACK);
float radius=Math.min(avatar.getWidth(), avatar.getHeight())/2;
canvas.drawCircle(avatar.getWidth()/2, avatar.getHeight()/2, radius, paint);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawBitmap(avatar, 0, 0,paint);
paint.setColor(Color.WHITE);
paint.setStyle(Style.STROKE);
float strokeWidth = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 2, context.getResources().getDisplayMetrics());
paint.setStrokeWidth(strokeWidth);
canvas.drawCircle(avatar.getWidth()/2, avatar.getHeight()/2, radius - strokeWidth/2, paint);
return bitmap;
}