ios实现下载图片的裁减和显示

使用如下的方法可以裁减的同时保证了不丢失像素。

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    // Set appIcon and clear temporary data/image
    UIImage *image = [[UIImage alloc] initWithData:self.activeDownload];
    
    if (image.size.width != kAppIconSize || image.size.height != kAppIconSize)
    {
        
        //set the frame for the picture
        CGSize itemSize = CGSizeMake(kAppIconSize, kAppIconSize);
        
        //if the width is differ from height,than check
        if (image.size.width < image.size.height) {
            
            itemSize.width = (image.size.width/image.size.height)*kAppIconSize;
            NSLog(@"the width cut is %f",itemSize.width);
            
        }
        //       self.kids.appIcon = [self resizeToSize:itemSize withOrignalSize:image.size withImage:image thenCropWithRect:CGRectMake(0, 0, 70.0f, 70.0f)];
        UIGraphicsBeginImageContextWithOptions(itemSize, NO, 0.0f);
        CGRect imageRect = CGRectMake(0.0, 0.0, itemSize.width, itemSize.height);
        NSLog(@"the picture width is %f %f",image.size.width,image.size.height);
        [image drawInRect:imageRect];
        self.kids.appIcon = UIGraphicsGetImageFromCurrentImageContext();
        NSLog(@"the picture end width is %f %f",self.kids.appIcon.size.width,self.kids.appIcon.size.height);
        UIGraphicsEndImageContext();
    }
    else
    {
        self.kids.appIcon = image;
    }
    [image release];
    self.activeDownload = nil;
    
    // Release the connection now that it's finished
    self.imageConnection = nil;
    
    // call our delegate and tell it that our icon is ready for display
    if (self.completionHandler)
        self.completionHandler();
    
}

然后需要注意的是，使用uibutton要使用setimage而不是setbackgroundimage来加载图片。否则显示的图片总是70X70的kAppIconSize的大小当图片宽高比例明显不同时候就会出现拉伸。所以要注意。

然后使用setcontentmode来控制一下显示的内容才会有效。