对图片进行压缩

                dataImage = UIImageJPEGRepresentation(imageReadyPost, 1.0);
                NSUInteger sizeOrigin = [dataImage length];
                NSUInteger sizesizeOriginKB = sizeOrigin / 1024;
                
                // 图片大于500k要先进行压缩 
                if (sizesizeOriginKB > 500)
{
                    float a = 500.00000;
                    float  b = (float)sizesizeOriginKB;
                    float q = sqrt(a/b);
                    CGSize sizeImage = [imageReadyPost size];
                    CGFloat iwidthSmall = sizeImage.width * q;
                    CGFloat iheightSmall = sizeImage.height * q;
                    CGSize itemSizeSmall = CGSizeMake(iwidthSmall, iheightSmall);
                    UIGraphicsBeginImageContext(itemSizeSmall);
                    CGRect imageRectSmall = CGRectMake(0.0f, 0.0f, itemSizeSmall.width, itemSizeSmall.height);
                    [imageReadyPost drawInRect:imageRectSmall];
                    UIImage *SmallImage = UIGraphicsGetImageFromCurrentImageContext();
                    UIGraphicsEndImageContext();
                    NSData *dataImageSend = UIImageJPEGRepresentation(SmallImage, 1.0);
                    dataImage = dataImageSend;
｝
最后把dataImage发送出去