iOS 根据UIImage 修改UIImageView Frame （包括截取图片中间部分）

iOS UIImageView 根据需求调整frame

1、图片的宽和高不相等，截取图片的中间部分，截取的部分Size明确

2、图片的宽度要等于其父视图的类的宽度，然后根据宽度计算高度，保证

图片不变形，显示正常

3、图片的宽度或高度大于其父视图的类的宽的或高度，如果是宽度的问题，

就以其父视图的宽度为准，确定图片的显示宽度；如果是高度的问题，就以

其父视图的高度为准，确定图片的显示高度。

以上三种情况，具体示例依次如下：

第一种情况,调用方法：

- (void)imageLoadedFinish:(UrlImageView *)oldImageView image:(UIImage *)imageV skuInfo:(NSDictionary *)skuInfo

{
      截取的目标尺寸

       float imgW = (WIN_SIZE.width-40)/3;

        //截取中间部分

        oldImageView.image = [self squareImageFromImage:imageV scaledToSize:imgW];

}

－－－截图操作 //截取中间部分

- (UIImage *)squareImageFromImage:(UIImage *)image scaledToSize:(CGFloat)newSize

{

   －－缩放比例

    CGAffineTransform scaleTransform;

    CGPoint origin;

    图片大小大于图片高度的情况

    if (image.size.width > image.size.height)

    {

        //image原始高度为200，缩放image的高度为400pixels，所以缩放比率为2

 计算缩放比例

       CGFloat scaleRatio = newSize / image.size.height;

        scaleTransform = CGAffineTransformMakeScale(scaleRatio, scaleRatio);

        //设置绘制原始图片的画笔坐标为CGPoint(-100, 0)pixels

      计算画笔的X轴

        origin = CGPointMake(-(image.size.width - image.size.height) / 2.0f, 0);

    } else

    {

      图片的高度大于宽度的情况

        CGFloat scaleRatio = newSize / image.size.width;

        scaleTransform = CGAffineTransformMakeScale(scaleRatio, scaleRatio);

        计算画笔的Y轴

        origin = CGPointMake(0, -(image.size.height - image.size.width) / 2.0f);

    }

    CGSize size = CGSizeMake(newSize, newSize);

    //创建画板为(400x400)pixels

    if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)])

    {

        UIGraphicsBeginImageContextWithOptions(size, YES, 0);

    } else

    {

        UIGraphicsBeginImageContext(size);

    }

 CGContextRef context = UIGraphicsGetCurrentContext();

    //将image原始图片(400x200)pixels缩放为(800x400)pixels

    CGContextConcatCTM(context, scaleTransform);

    //origin也会从原始(-100, 0)缩放到(-200, 0)

    [image drawAtPoint:origin];

    //获取缩放后剪切的image图片

    image = UIGraphicsGetImageFromCurrentImageContext();

    结束画板绘制

    UIGraphicsEndImageContext();

    return image;

}

第二种情况：

      //等比例缩放

{    得到当前视图的frame

        CGSize selfSize = self.frame.size;

       得到image的frame

        CGSize imageSize = imageV.size;

       得到imageView 的frame

        CGRect imageVRect = self.imageView.frame;

       确定imageView 的宽度

        imageVRect.size.width = selfSize.width;

       根据宽度计算imageView 的高度

        imageVRect.size.height = imageVRect.size.width*imageSize.height/imageSize.width;

        //计算x，y

        imageVRect.origin.x = 0;

        imageVRect.origin.y = 0;

        self.imageView.frame = imageVRect;

        CGRect selfRect = self.frame;

        selfRect.size.width = imageVRect.size.width;

        selfRect.size.height = imageVRect.size.height;

        self.frame = selfRect;

}

第三种情况：

//等比例缩放

(void)imageLoadedFinish:(UrlImageView *)oldImageView image:(UIImage *)imageV skuInfo:(NSDictionary *)skuInfo

{     

       得到当前视图的frame

       CGSize selfSize = self.frame.size;

       得到当前Image的frame

        CGSize imageSize = imageV.size;

       得到当前ImageView 的frame

        CGRect imageVRect = self.imageView.frame;

       image的宽度大于当前视图的宽度

        if(imageSize.width > selfSize.width)

        {

            根据宽度计算高度，确定宽度

            imageVRect.size.height = selfSize.width * imageSize.height / imageSize.width;

            imageVRect.size.width = selfSize.width;

        }

        image的高度大于当前视图的高度

        if(imageVRect.size.height > selfSize.height)

        {

根据高度计算宽度，确定宽度

            imageVRect.size.width = selfSize.height * imageVRect.size.width  / imageVRect.size.height;

            imageVRect.size.height = selfSize.height;

        }

//计算x，y

        imageVRect.origin.x = (selfSize.width-imageVRect.size.width)/2;

        imageVRect.origin.y = (selfSize.height-imageVRect.size.height)/2;

        self.imageView.frame = imageVRect;

}