图片裁剪，左右超出了等距裁剪图片左右部分 上下超出了就等距裁剪图片上下部分

+ (UIImage *)handleImage:(UIImage *)originalImage withSize:(CGSize)size

{

    

    CGSize originalsize = [originalImage size];

    NSLog(@"改变前图片的宽度为%f,图片的高度为%f",originalsize.width,originalsize.height);

    //原图长宽均小于标准长宽的，不作处理返回原图

    if (originalsize.width<size.width && originalsize.height<size.height)

    {

        return originalImage;

        

    }//原图长宽均大于标准长宽的，按比例缩小至最大适应值

    else if(originalsize.width>size.width && originalsize.height>size.height)

    {

        CGFloat rate = 1.0;

        CGFloat widthRate = originalsize.width/size.width;

        CGFloat heightRate = originalsize.height/size.height;

        

        rate = widthRate>heightRate?heightRate:widthRate;

        

        CGImageRef imageRef = nil;

        

        if (heightRate>widthRate)

        {

            imageRef = CGImageCreateWithImageInRect([originalImage CGImage], CGRectMake(0, originalsize.height/2-size.height*rate/2, originalsize.width, size.height*rate));//获取图片整体部分

        }

        else

        {

            imageRef = CGImageCreateWithImageInRect([originalImage CGImage], CGRectMake(originalsize.width/2-size.width*rate/2, 0, size.width*rate, originalsize.height));//获取图片整体部分

        }

        UIGraphicsBeginImageContext(size);//指定要绘画图片的大小

        CGContextRef con = UIGraphicsGetCurrentContext();

        

        CGContextTranslateCTM(con, 0.0, size.height);

        CGContextScaleCTM(con, 1.0, -1.0);

        

        CGContextDrawImage(con, CGRectMake(0, 0, size.width, size.height), imageRef);

        UIImage *standardImage = UIGraphicsGetImageFromCurrentImageContext();

        NSLog(@"改变后图片的宽度为%f,图片的高度为%f",[standardImage size].width,[standardImage size].height);

        

        UIGraphicsEndImageContext();

        CGImageRelease(imageRef);

        

        return standardImage;

    }

    

    //原图长宽有一项大于标准长宽的，对大于标准的那一项进行裁剪，另一项保持不变

    else if(originalsize.height>size.height || originalsize.width>size.width)

    {

        CGImageRef imageRef = nil;

        

        if(originalsize.height>size.height)

        {

            imageRef = CGImageCreateWithImageInRect([originalImage CGImage], CGRectMake(0, originalsize.height/2-size.height/2, originalsize.width, size.height));//获取图片整体部分

        }

        else if (originalsize.width>size.width)

        {

            imageRef = CGImageCreateWithImageInRect([originalImage CGImage], CGRectMake(originalsize.width/2-size.width/2, 0, size.width, originalsize.height));//获取图片整体部分

        }

        

        UIGraphicsBeginImageContext(size);//指定要绘画图片的大小

        CGContextRef con = UIGraphicsGetCurrentContext();

        

        CGContextTranslateCTM(con, 0.0, size.height);

        CGContextScaleCTM(con, 1.0, -1.0);

        

        CGContextDrawImage(con, CGRectMake(0, 0, size.width, size.height), imageRef);

        

        UIImage *standardImage = UIGraphicsGetImageFromCurrentImageContext();

        NSLog(@"改变后图片的宽度为%f,图片的高度为%f",[standardImage size].width,[standardImage size].height);

        

        UIGraphicsEndImageContext();

        CGImageRelease(imageRef);

        

        return standardImage;

    }

    

    //原图为标准长宽的，不做处理

    else

    {

        return originalImage;

    }

}