通过颜色生成图片，直接上代码

CGRect rect = CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, 64);

UIGraphicsBeginImageContext(rect.size);

CGContextRef context = UIGraphicsGetCurrentContext();

UIColor *color = [UIColor colorWithRed:41/255.0 green:182/255.0 blue:246/255.0 alpha:1.0];

CGContextSetFillColorWithColor(context, [color CGColor]);

CGContextFillRect(context, rect);

UIImage *img = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

此时 img 就是生成的图片