Objective-C缩放image适应imageview的大小

最新推荐文章于 2025-02-18 11:02:09 发布

原创最新推荐文章于 2025-02-18 11:02:09 发布 · 380 阅读

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#objective-c #ios #开发语言

本文介绍如何在Objective-C中使用代码使图片自动缩放以适应UIImageView的大小，确保图片在显示时始终保持正确的比例，从而优化iOS应用的用户体验。


- (void)viewDidLoad {
    [super viewDidLoad];


    //如果要实现放大缩小窗口的时候,imageview中的图片随之变化大小的话，要实现一个监听窗口大小的动作，NSWindowDidResizeNotification

     self.img.image = [self resizeImage:[NSImage imageNamed:@"0.88881.png"] size:NSMakeSize(self.img.frame.size.width, self.img.frame.size.height)];
   
}

- (NSImage*) resizeImage:(NSImage*)sourceImage size:(NSSize)size{
    
    NSRect targetFrame = NSMakeRect(0, 0, size.width, size.height);
    NSImage*  targetImage = [[NSImage alloc] initWithSize:size];
    
    NSSize sourceSize = [sourceImage size];
    
    float ratioH = size.height/ sourceSize.height;
    float ratioW = size.width / sourceSize.width;
    
    NSRect cropRect = NSZeroRect;
    
    if (ratioH >= ratioW) {
        cropRect.size.width = floor (size.width / ratioH);
        cropRect.size.height = sourceSize.height;
    } else {
        cropRect.size.width = sourceSize.width;
        cropRect.size.height = floor(size.height / ratioW);
    }
    
    cropRect.origin.x = floor( (sourceSize.width - cropRect.size.width)/2 );
    cropRect.origin.y = floor( (sourceSize.height - cropRect.size.height)/2 );
    
    
    [targetImage lockFocus];
    
    [sourceImage drawInRect:targetFrame
                   fromRect:cropRect       //portion of source image to draw
                  operation:NSCompositeCopy  //compositing operation
                   fraction:1.0              //alpha (transparency) value
             respectFlipped:YES              //coordinate system
                      hints:@{NSImageHintInterpolation:
                                  [NSNumber numberWithInt:NSImageInterpolationLow]}];
    
    [targetImage unlockFocus];
    
    return targetImage;
}