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

-(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;

}