如何读取OSX的物理屏幕尺寸? [英] How to read the physical screen size of OSX?

问题描述

我想知道Mac OSX下的物理屏幕尺寸.但是NSDeviceResolution总是报告错误的值(72)，因此分辨率/dpi的计算结果是错误的.

I would like to know the physical screen size under Mac OSX. But NSDeviceResolution is always reporting wrong value (72), so the calculation result of resolution / dpi is wrong.

在关于本机"内，有一个Mac型号的琴弦，我的是"15英寸，2011年初".因此，我想知道是否应该有一种方法(可能在obj-c中)读取该字符串，然后将其用作物理屏幕尺寸.

Inside "About This Mac", there is a Mac model string there, mine is "15-inch, Early 2011". So I'm wondering should there be a way (in obj-c probably), to read that string and then I can use that as the physical screen size.

感谢您的帮助.

推荐答案

您可以使用 CGDisplayScreenSize 来获取屏幕的物理尺寸(以毫米为单位).假设您已经知道分辨率，则可以从中计算DPI.

You can use CGDisplayScreenSize to get the physical size of a screen in millimetres. From that you can compute the DPI given that you already know the resolution.

例如.

NSScreen *screen = [NSScreen mainScreen];
NSDictionary *description = [screen deviceDescription];
NSSize displayPixelSize = [[description objectForKey:NSDeviceSize] sizeValue];
CGSize displayPhysicalSize = CGDisplayScreenSize(
            [[description objectForKey:@"NSScreenNumber"] unsignedIntValue]);

NSLog(@"DPI is %0.2f", 
         (displayPixelSize.width / displayPhysicalSize.width) * 25.4f); 
         // there being 25.4 mm in an inch

该@"NSScreenNumber"内容看起来很狡猾，但它是明确记录的手段NSScreen获得CGDirectDisplayID的a>.

That @"NSScreenNumber" thing looks dodgy but is the explicit documented means of obtaining a CGDirectDisplayID from an NSScreen.

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