iOS：等比压缩截图代码

+(UIImage *)comPRessImageWith:(UIImage *)image width:(float)width height:(float)height{    float imageWidth = image.size.width;    float imageHeight = image.size.height;        float widthScale = imageWidth /width;    float heightScale = imageHeight /height;        // 创建一个bitmap的context    // 并把它设置成为当前正在使用的context    UIGraphicsBeginImageContext(CGSizeMake(width, height));        if (widthScale > heightScale) {        [image drawInRect:CGRectMake(0, 0, imageWidth /heightScale , height)];        }    else {        [image drawInRect:CGRectMake(0, 0, width , imageHeight /widthScale)];    }        // 从当前context中创建一个改变大小后的图片    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();    [newImage retain];    // 使当前的context出堆栈    UIGraphicsEndImageContext();        return newImage;    }