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