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;
}