色彩校样

备注

色彩校样仅在启用画布显卡加速时才能生效。

如果我们需要打印 Krita 制作的图像，我们有时会发现屏幕上显示的效果跟打印出来的效果不太一样。有时候颜色深了，有时候颜色浅了，有时候红色会更冲，有时候反差弱化了。如果只是在打印一些简单的文档，这点小事没什么大不了的。然而到了专业印刷场景里这就是印刷事故了，毕竟颜色的偏差可能会严重影响图像的视觉效果。

为什么会发生偏色呢？这是因为显示器使用的 RGB 色彩模型和打印机的 CMYK 模型不同，打印机能够使用的色域往往更小。

有些人会天真地以为：那我们在 CMYK 色彩模型下面工作不就行了嘛！但这种想法其实有三大问题：

  • 在 CMYK 空间下绘画并无法保证颜色就一定能与打印机的输出效果完全一致。因为不同的油墨、纸张和印刷设备的组合会产生无数的色域变化，每个不同组合都会有一个与之匹配的特性文件。

  • 即使你的工作特性文件和打印机的输出特性文件完全一致，CMYK 本身依然是一种难以预测的色彩空间。色彩运算在 CMYK 空间下面的结果要比在其他空间中的要差，混合模式的结果也跟其他空间下面的大不相同。

  • 最后，在一个特定的 CMYK 空间下面工作意味着制作的文件会被限制在该空间狭窄的色域里。如果你要为另一个不同的 CMYK 特性文件作印前准备，由于纸张、打印机和油墨发生了变化，可以使用的色域说不定就变大了，可是你的旧文件却无法发挥新设备的潜力。

所以在理想状况下，你应该在 RGB 空间下面绘制图像，使用你习惯的 RGB 图像工具，然后让计算机随时切换到某个 CMYK 空间下面对颜色进行校对。这种技术早已成为现实，我们把它叫做“色彩校样(电子校样)”。

../_images/Softproofing_regularsoftproof.png

左边的是原图，右边的是一个色彩校样功能启用后的视图。两者的区别相当微妙，这是因为原图并未使用特别明亮的颜色。但我们不难发现在右边的色彩校样视图里，花朵的白色没有原图那么偏青蓝，而叶子的绿色也没有原图那么鲜艳。

You can toggle soft proofing on any image using the Ctrl + Y shortcut. Unlike other programs, this is per-view, so that you can look at your image non-proofed and proofed, side by side. The proofing configuration can also be set per image, and saved into the .kra file. Just enable Store Softproofing configuration in the image in the proofing options in Image ‣ Image Properties ‣ Soft Proofing. If the checkbox is unchecked, then Krita will use global settings from Settings ‣ Configure Krita… ‣ Color Management ‣ Soft Proofing (for more details see here).

备注

When Store Softproofing configuration in the image is enabled, Krita embeds the entire proofing ICC profile into .kra file. This ICC profile can be big for some output devices, especially CMYK ones.

色彩校样功能有下列选项：

Model, Profile

这三个选项里只有“特性”一项是特别重要的。特性文件是色彩校样的目标文件。在专业打印流程中，此特性文件应该由印刷公司决定。

Conversion Rendering Intent

Set the intent used to convert the image to the proofed output device profile. It uses the same options as the intents mentioned in the color managed workflow. This intent should coincide with the conversion intent used by your print house before printing. If your print house does not do any conversion internally, then you should perform the conversion yourself before sending the file to them.

../_images/Softproofing_adaptationstate.png

Left: Soft proofed image with Absolute Intent Chromatic Adaptation enabled. Right: Soft proofed image with Absolute Intent Chromatic Adaptation disabled.

Conversion Black Point Compensation

Enables the black point compensation when converting image to the proofed output device profile. Turning this off will clip the shadow values to the minimum that either the screen and the proofing profile can handle, while turning this on will scale the black to the screen-range, showing you the full range of grays in the image. Like Conversion Rendering Intent, this value should coincide with the value used by the printing house when performing conversion to the device.

Display Model

Defines the way how the proofed (and possibly clipped) space will be shown on the screen.

  • Use global display settings instructs Krita to render the proofed space using the global settings, set in Settings ‣ Configure Krita… ‣ Color Management ‣ Display.

  • Simulate paper white and black is used to preview the white point (or “color tint”) of the paper on the current display. In other words, if the paper is matte, or metallic, or has some sort of sepia effect, this will be visible on your screen. Please take it into account that the viewing conditions’ white point will still be adjusted to the one of the screen. It means that you cannot visually compare the physical print and the image on the screen, unless all three white points coincide: the one in the paper profile, the one the display is configured to and the white point of the light bulb that illuminates your physical print.

  • Custom allows you to configure the final conversion step manually. You may want to configure the pipeline depending on your goal:

    Preview color gamut (or “color variety”) of the image

    • Rendering Intent –> Relative Colorimetric

    • Black Point Compensation –> Enabled

    备注

    If you want to use Out of Gamut Warnings, it is best to use them in this mode

    Preview contrast degradations caused by the color of the paper

    • Rendering Intent –> Absolute Colorimetric

    • Absolute Intent Chromatic Adaptation –> Enabled

    警告

    If you are using Wayland compositor, Absolute Colorimetric intent may be broken (even in XWayland mode). More than that, it may be broken differently in different versions.

    In KWin 6.4.x and earlier, Absolute Colorimetric will behave as if Absolute Intent Chromatic Adaptation is always disabled. It will cause severe color tint if white points (sigChromaticAdaptationTag) of the printer and display profiles do not coincide.

    In KWin 6.5.x and later, Absolute Colorimetric will behave as if Absolute Intent Chromatic Adaptation is always enabled. Given that you keep the checkbox set, the feature will work correctly and will let you preview contrast degradations, but you will not be able to get advanced effects of disabling color adaptation to the display space.

    This is a problem of the Wayland protocol specification, the fix is discussed here.

色域警告

Set the color of Out of Gamut Warnings.

You can set the defaults that Krita uses in Settings ‣ Configure Krita… ‣ Color Management ‣ Soft Proofing.

为了确保选项配置正确，我们推荐把图像在安装正确的打印机上进行试印，然后把样张跟屏幕色彩校样的效果进行比对，以决定是否进一步调整色彩校样的选项。

超出色域警告

超出色域警告色，也叫做色域警告，是色彩校样的一个附加功能。它使用被指定的警告色来标记那些无法被包含在色彩校样特性文件色域内的颜色。

此功能有助于发现潜在的反差损失，让你可以有针对性地调低图像的色彩反差。

../_images/Softproofing_gamutwarnings.png

左图：原图视图，右图：启用了色域警告色的色彩校样视图。Krita 会在 KRA 图像的色彩校样选项中保存色域警告色。你可以为你的当前图像选择一种易于发现的警告色。

要激活色域警告色，按 Ctrl + Shift + Y ，但要让此功能完整地工作，你必须同时激活色彩校样功能。

备注

色彩校样在浮点空间下面无法正常工作，会造成错误的色域警告色显示。因此在浮点空间下色彩校样会被禁用。

警告

色域警告色有时候会在线性特性文件下面对暗部颜色给出莫名其妙的警告。这是 LittleCMS 的一个程序缺陷，你可以 在此 阅读相关信息。