为什么MVC不是一种设计模式？

@interface UIImage(UIImageScale)
-(UIImage*)getSubImage:(CGRect)rect;
-(UIImage*)scaleToSize:(CGSize)size;
@end

@implementation UIImage(UIImageScale)

//截取部分图像
-(UIImage*)getSubImage:(CGRect)rect
{
CGImageRef subImageRef = CGImageCreateWithImageInRect(self.CGImage, rect);
CGRect smallBounds = CGRectMake(0, 0, CGImageGetWidth(subImageRef), CGImageGetHeight(subImageRef));

UIGraphicsBeginImageContext(smallBounds.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextDrawImage(context, smallBounds, subImageRef);
UIImage* smallImage = [UIImage imageWithCGImage:subImageRef];
UIGraphicsEndImageContext();

return smallImage;
}

//等比例缩放
-(UIImage*)scaleToSize:(CGSize)size
{
CGFloat width = CGImageGetWidth(self.CGImage);
CGFloat height = CGImageGetHeight(self.CGImage);

float verticalRadio = size.height*1.0/height;
float horizontalRadio = size.width*1.0/width;

float radio = 1;
if(verticalRadio>1 && horizontalRadio>1)
{
radio = verticalRadio > horizontalRadio ? horizontalRadio : verticalRadio;
}
else
{
radio = verticalRadio < horizontalRadio ? verticalRadio : horizontalRadio;
}

width = width*radio;
height = height*radio;

int xPos = (size.width - width)/2;
int yPos = (size.height-height)/2;

// 创建一个bitmap的context
// 并把它设置成为当前正在使用的context
UIGraphicsBeginImageContext(size);

// 绘制改变大小的图片
[self drawInRect:CGRectMake(xPos, yPos, width, height)];

// 从当前context中创建一个改变大小后的图片
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();

// 使当前的context出堆栈
UIGraphicsEndImageContext();

// 返回新的改变大小后的图片
return scaledImage;
}
@end