cocoa - 对 NSImageView 缩放感到困惑

Question

我正在尝试显示一个简单的 NSImageView ，其图像居中，而不像这样缩放:

就像 iOS 所做的那样，当您设置 UIView 的 contentMode = UIViewContentModeCenter

所以我尝试了所有NSImageScaling值，这就是我选择NSScaleNone时得到的结果

我真的不明白发生了什么:-/

Answer 1

您可以手动生成正确大小和内容的图像，并将其设置为 NSImageView 的图像，这样 NSImageView 不需要做任何事情。

NSImage *newImg = [self resizeImage:sourceImage size:newSize];
[aNSImageView setImage:newImg];

以下函数调整图像大小以适应新尺寸，同时保持纵横比不变。如果图像小于新尺寸，则会放大图像并填充新框架。如果图像大于新尺寸，则会缩小尺寸，并填充新框架

- (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;}