UIImage 等比率缩放

最近遇到了 APP 启动页面（第一次启动时）图片略大的问题，因此想到了等比率缩放的问题。

一番查找之后，果真找到了解决办法，缩放方法的代码如下：

- (UIImage *)scaleImage:(UIImage *)image toScale:(float)scaleSize
{
    UIGraphicsBeginImageContext(CGSizeMake(image.size.width * scaleSize, image.size.height * scaleSize);
    [image drawInRect:CGRectMake(0, 0, image.size.width * scaleSize, image.size.height * scaleSize)];
    UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return scaledImage;
}

上述是根据图片自身的大小进行的等比率缩放。这里根据实际需要，调整为根据屏幕的宽高设置图片的大小，代码如下：

- (UIImage *)scaleImage:(UIImage *)image toScale:(float)scaleSize 
{
    UIGraphicsBeginImageContext(CGSizeMake([UIScreen mainScreen].bounds.size.width * scaleSize, [UIScreen mainScreen].bounds.size.width * scaleSize));
    [image drawInRect:CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width * scaleSize, [UIScreen mainScreen].bounds.size.width * scaleSize)];
    UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return scaledImage;
}