通过UIGraphics重新设置image的大小

UIImage *icon = [UIImage imageNamed:@"图片"];CGSize itemSize = CGSizeMake(20, 20);//设置要显示的width跟heightUIGraphicsBeginImageContextWithOptions(itemSize, NO,0.0);CGRect imageRect = CGRectMake(0.0, 0.0, itemSize.width, itemSize.height);[icon drawInRect:imageRect];        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();UIGraphicsEndImageContext();