NSImage 大小不是一些图片的真实大小? [英] NSImage size not real size with some pictures?

问题描述

我看到有时 NSImage 大小不是真实大小(有一些图片)而 CIImage 大小总是真实的.我正在用这个图像进行测试.

I see that sometimes NSImage size is not real size (with some pictures) and CIImage size is always real. I was testing with this image.

这是我为测试而编写的源代码:

This is source code which I wrote for testing:

NSImage *_imageNSImage = [[NSImage alloc]initWithContentsOfFile:@"<path to image>"];

NSSize _dimensions = [_imageNSImage size];

[_imageNSImage release];

NSLog(@"Width from CIImage: %f",_dimensions.width);
NSLog(@"Height from CIImage: %f",_dimensions.height);




NSURL *_myURL = [NSURL fileURLWithPath:@"<path to image>"];
CIImage *_imageCIImage = [CIImage imageWithContentsOfURL:_myURL];


NSRect _rectFromCIImage = [_imageCIImage extent];

NSLog(@"Width from CIImage: %f",_rectFromCIImage.size.width);
NSLog(@"Height from CIImage: %f",_rectFromCIImage.size.height);

输出为:

那怎么可能??也许我做错了什么?

推荐答案

NSImage size 方法返回与屏幕分辨率相关的尺寸信息.要获得实际文件图像中表示的大小，您需要使用 NSImageRep.您可以使用 representations 方法从 NSImage 获取 NSImageRep.或者，您可以像这样直接创建 NSBitmapImageRep 子类实例:

NSImage size method returns size information that is screen resolution dependent. To get the size represented in the actual file image you need to use an NSImageRep. You can get an NSImageRep from an NSImage using the representations method. Alternatively you can create a NSBitmapImageRep subclass instance directly like this:

NSArray * imageReps = [NSBitmapImageRep imageRepsWithContentsOfFile:@"<path to image>"];

NSInteger width = 0;
NSInteger height = 0;

for (NSImageRep * imageRep in imageReps) {
    if ([imageRep pixelsWide] > width) width = [imageRep pixelsWide];  
    if ([imageRep pixelsHigh] > height) height = [imageRep pixelsHigh];  
}

NSLog(@"Width from NSBitmapImageRep: %f",(CGFloat)width);
NSLog(@"Height from NSBitmapImageRep: %f",(CGFloat)height);

循环考虑到某些图像格式可能包含多个图像(例如 TIFF).

The loop takes into account that some image formats may contain more than a single image (such as TIFFs for example).

您可以使用以下命令创建此大小的 NSImage:

You can create an NSImage at this size by using the following:

NSImage * imageNSImage = [[NSImage alloc] initWithSize:NSMakeSize((CGFloat)width, (CGFloat)height)];
[imageNSImage addRepresentations:imageReps];

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