等比压缩图片的方法

- (UIImage*)imageEqualRatioScaledToSize:(CGSize)targetSize

{

    UIImage *sourceImage = self;

    UIImage *newImage = nil;

    CGSize imageSize = sourceImage.size;

    CGFloat srcWidth = imageSize.width;

    CGFloat srcHeight = imageSize.height;

    CGFloat targetWidth = targetSize.width;

    CGFloat targetHeight = targetSize.height;

    

    if (srcWidth <= targetWidth && srcHeight <= targetHeight) {

        // 如果源图已经小于缩放尺寸，则返回源图

        newImage = sourceImage;

    } else {

        // 如果源图长或宽大于缩放尺寸，则等比缩放

        double scale = (double)targetWidth/srcWidth < (double)targetHeight/srcHeight ? (double)targetWidth/srcWidth : (double)targetHeight/srcHeight;

        

        CGFloat scaleWidth = scale * srcWidth;

        CGFloat scaleHeight = scale * srcHeight;

        

        CGSize newSize = CGSizeMake(scaleWidth, scaleHeight);

        UIGraphicsBeginImageContext(newSize);

        

     

        CGRect thumbnailRect = CGRectMake(0, 0, scaleWidth, scaleHeight);

        [sourceImage drawInRect:thumbnailRect];

        newImage = UIGraphicsGetImageFromCurrentImageContext();

        

        if(newImage == nil)

            DLog(@"could not scale image");

        UIGraphicsEndImageContext();

    }

    return newImage;

}