ios 在 iPad 上显示 PDF 文档 - 颜色问题
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Displaying PDF documents on iPad - Color Problems
提问by Brandon
I've built a PDF reader for the iPad and I've noticed some color problems when doing a side-by-side comparison of the document in preview verus the simulator and device.
我已经为 iPad 构建了一个 PDF 阅读器，并且在将预览中的文档与模拟器和设备进行并排比较时发现了一些颜色问题。
The best way to describe it is to say that the colors have become more intense. Any discrepancies between similar colors used in close proximity have become more noticeable while all the colors seem brighter in general.
描述它的最佳方式是说颜色变得更加强烈。近距离使用的相似颜色之间的任何差异都变得更加明显，而所有颜色总体上看起来更亮。
回答by Tommy
Despite the hype connecting the iPad to the print industry, it doesn't supply a device calibrated CMYK profile installed. As a result, any PDFs with CMYK content tend to look quite crazy. Conversely, I believe that it handles conversions from Adobe RGB to the iPad's screen very well indeed, so you'd be highly recommended to find a way to adjust how you're outputting your PDFs or to find a tool that can do a conversion after the fact.
尽管大肆宣传将 iPad 与印刷行业联系起来，但它并未提供已安装的设备校准 CMYK 配置文件。因此，任何带有 CMYK 内容的 PDF 往往看起来很疯狂。相反，我相信它确实可以很好地处理从 Adobe RGB 到 iPad 屏幕的转换，因此强烈建议您找到一种方法来调整您输出 PDF 的方式或找到一种可以在之后进行转换的工具事实。
I've dealt with this only from the implementation side so don't have direct experience, but I believe that at least in InDesign it's a simple export toggle.
我只从实现方面处理过这个问题，所以没有直接经验，但我相信至少在 InDesign 中，它是一个简单的导出切换。
回答by Autumn DeSellem
When I wrote that I forgot to consider that the bitmap images I was using were EXPORTED for the web from Photoshop (i.e. save for web), and therefore by default, they displayed correctly. Looking at my print PDFs that have images embedded in them, I can see that any of them that use the wrong profile have high contrast and bad coloring in the images and the vector elements.
当我写到我忘记考虑我使用的位图图像是从 Photoshop 导出到网络的（即保存为网络），因此默认情况下，它们显示正确。查看我嵌入了图像的打印 PDF，我可以看到其中任何一个使用错误配置文件的图像和矢量元素都具有高对比度和不良着色。
I suggest that for images you want to display on the iPad, that you try either exporting them for web, making sure that you have enough resolution to look good on the iPad, or else saving them with an RGB profile, either Adobe RGB or working sRGB - see which looks best.
我建议对于您想要在 iPad 上显示的图像，您尝试将它们导出到网络，确保您有足够的分辨率在 iPad 上看起来不错，或者使用 RGB 配置文件保存它们，Adobe RGB 或工作sRGB - 看看哪个看起来最好。
Note that there is a difference between "assigning" a color profile and "converting" to a color profile, as one of them is "destructive" and degrades the image quality a bit when making the conversion, and the other is not. You might try both with your images - save a series with a combination of these 2 variables - which profile and which method to get there - and see what works best with your images.
请注意，“分配”颜色配置文件和“转换”到颜色配置文件之间存在差异，因为其中一个是“破坏性的”，并且在进行转换时会稍微降低图像质量，而另一个则不是。您可以尝试使用您的图像 - 使用这 2 个变量的组合保存一个系列 - 哪个配置文件和到达那里的方法 - 并查看哪些最适合您的图像。
I might do the experiment myself soon with different types of images and see what looks best on the iPad.
我可能很快就会用不同类型的图像自己做实验，看看什么在 iPad 上看起来最好。
Keep in mind that sRGB profile was created for computer monitors and Adobe RGB 1998 is a good RGB profile for digital printing (and more), but the iPad is neither really - maybe soon there will be a profile created for it :). Since I haven't tested it in-depth I'd suggest you try both and see what turns out true-to-color for you.
请记住，sRGB 配置文件是为计算机显示器创建的，而 Adobe RGB 1998 是用于数字打印（以及更多）的良好 RGB 配置文件，但 iPad 两者都不是——也许很快就会为它创建一个配置文件:)。由于我尚未对其进行深入测试，因此我建议您同时尝试这两种方法，看看哪种颜色对您来说是真实的。
There are a couple of good blogs I have seen about using Photoshop for iPhone & iPad design. This one seems to be in-depth. I plan on reading it soon:
我看到了一些关于在 iPhone 和 iPad 设计中使用 Photoshop 的好博客。这个好像很深入。我打算尽快阅读：
回答by Autumn DeSellem
When you use Pantone colors, they do not contain RGB definitions that are embedded within the document - they are, by default, for ptint. Therefore when you use Pantone or CMYK colors, if you do not export correctly they will be way off.
当您使用 Pantone 颜色时，它们不包含嵌入文档中的 RGB 定义 - 默认情况下，它们用于 ptint。因此，当您使用 Pantone 或 CMYK 颜色时，如果您没有正确导出，它们将会消失。
When you export your document from InDesign to a PDF, select the "Output" tab and choose "Convert to destination". Then set the destination to Adobr RGB 1998. Make sure that "Include destination profile" is selected.
将文档从 InDesign 导出为 PDF 时，选择“输出”选项卡并选择“转换为目标”。然后将目标设置为 Adobr RGB 1998。确保选择了“包括目标配置文件”。
Alternatly, change the color profile in Acrobat.
或者，在 Acrobat 中更改颜色配置文件。
Normal computer monitors have a wider latitude and will display a range of color profiles in a way that is closer to the original, but the iPad is different. While bitmap files such as photos display properly, the color conversion in vector-based files is off.
普通电脑显示器的宽容度更广，会以更接近原始的方式显示一系列颜色配置文件，但 iPad 不同。虽然位图文件（例如照片）可以正常显示，但基于矢量的文件中的颜色转换已关闭。
I assume that the answer above that the iPad/iPhone "doesn't supply a device calibrated CMYK profile installed" is correct and that the reason is memory allocation & processing power - however that last part is a theory at this point.
我假设上面关于 iPad/iPhone“不提供已安装的设备校准 CMYK 配置文件”的答案是正确的，原因是内存分配和处理能力 - 然而，最后一部分是此时的理论。
回答by BastiBen
Did you hold the device next to your monitor to compare it?
您是否将设备放在显示器旁边进行比较？
If that's the case, I'm not surprised. I'm working in the printing industry and color matching is an important factor there.
如果是这样，我并不感到惊讶。我在印刷行业工作，颜色匹配是那里的一个重要因素。
What they do is to calibrate their monitors and screens using external color measuring devices. These devices (in combination with some driver software) allow to calculate the needed compensation to let the screen/monitor show color in a way it's going to be printed on paper.
他们所做的是使用外部颜色测量设备校准显示器和屏幕。这些设备（与一些驱动程序软件结合）允许计算所需的补偿，让屏幕/显示器以将要打印在纸上的方式显示颜色。
Unless you have such a device (to calibrate your screen to your iPad's screen), I doubt there is much you can do. The PDF is displayed by the underlying software in the same way as in your desktop machine, but the physical screen hardware works differently. Try the following: buy another monitor and compare it again. You'll see different results again.
除非你有这样的设备（将你的屏幕校准到 iPad 的屏幕），否则我怀疑你能做很多事情。PDF 由底层软件以与台式机相同的方式显示，但物理屏幕硬件的工作方式不同。尝试以下操作：购买另一台显示器并再次比较。你会再次看到不同的结果。
So my suggestion here is: do not trust the Simulator. The simulator is just there to allow quick testing of your code to see if everything works roughly as expected. What counts is how it looks/works on the hardware device!So always tune your software so it works correctly on the device, not the simulator.
所以我的建议是：不要相信 Simulator。模拟器只是为了快速测试您的代码，看看是否一切都按预期工作。重要的是它在硬件设备上的外观/工作方式！因此，请始终调整您的软件，使其在设备上正常运行，而不是在模拟器上运行。
TL;DR:It's due to different screens displaying colors differently. Make it work on the device, ignore visuals in the Simulator. Users are using the device, not the Simulator; and the device is mostly the same everywhere.
TL;DR：这是因为不同的屏幕显示的颜色不同。让它在设备上工作，忽略模拟器中的视觉效果。用户使用的是设备，而不是模拟器；并且设备在任何地方都大致相同。
回答by Autumn DeSellem
Also, I saw that somebody mentioned image FORMAT in addition to color.
另外，我看到有人除了颜色之外还提到了图像格式。
Although the iPad supports a few file types, if you were to develop an app you would NEED to provide .png images for the app. Also, if you take a screen shot from the iPad, it will supply you a .png file.
尽管 iPad 支持几种文件类型，但如果您要开发应用程序，则需要为应用程序提供 .png 图像。此外，如果您从 iPad 截屏，它会为您提供一个 .png 文件。
Since this is either an iPad-friendly or iPad-native format, I would suggest giving that a try.
由于这是 iPad 友好或 iPad 原生格式，我建议尝试一下。
回答by JapCon
Check your PDF source's Color Profile. If you intended to use it on iPad, sRGB or Apple RGB might be your friend.
检查您的 PDF 源的颜色配置文件。如果您打算在 iPad 上使用它，sRGB 或 Apple RGB 可能是您的朋友。
