ghostscript cmyk导出产生错误的黑色 [英] ghostscript cmyk export yields wrong black

问题描述

我正在尝试使用PSOcoated_v3.icc颜色配置文件将Inkscape创建的RGB-pdf文件转换为可打印的cmyk-pdf. PDF生成效果很好.但是，我想检查最终的颜色是否正确，尤其是黑色.因为我没有找到任何(免费)的工具来从最终的pdf文件中提取cmyk颜色，所以我认为作为第一步检查，我将RGB-pdf转换为cmyk-tiff并检查了黑色值.使用

I'm trying to convert an RGB-pdf file created by Inkscape to a print ready cmyk-pdf using PSOcoated_v3.icc color profile. PDF generation works fine. However, I'd like to check for correct final colors, especially for the black. As I did not found any (free) tool to pick the cmyk color from the final pdf I thought as a first check I convert the RGB-pdf to cmyk-tiff and check the black value. Doing so using

gs -q -dBATCH -dSAFER -dNOPAUSE \
-sDEVICE=tiff32nc \
-sDefaultRGBProfile=sRGB2014.icc \
-dOverrideICC \
-sOutputICCProfile=PSOcoated_v3.icc \
-sProcessColorModel=DeviceCMYK \
-sColorConversionStrategy=CMYK \
-sOutputFile=rgb.pdf \
 cmyk.tiff

产生cmyk黑色值[0.83，0.67，0.51，0.95].相反，当我使用libcms2将rgb(0,0,0)转换为cmyk时，我得到[0.92，0.64，0.45，0.96]，它与(几乎)有关PSOcoated_v3.icc配置文件的某些信息匹配，我发现

yields a cmyk black value of [0.83, 0.67, 0.51, 0.95]. Contrarily, when I use libcms2 to convert rgb (0,0,0) to cmyk I get [0.92, 0.64, 0.45, 0.96] which matches (almost) some information about the PSOcoated_v3.icc profile I found here. To confirmed that the source RGB-file black reads (0,0,0) I convert the RGB-pdf to an RGB-tiff and do find the black to be (0,0,0).

我是否在命令中缺少某些内容，可能是gs错误?

Am I missing something in the command of might this be a gs bug?

推荐答案

如果我在sRGB颜色空间中采用[0,0,0]的RGB颜色并将其转换为PSO涂层的v3 ICC配置文件定义的CMYK值在Photoshop中(使用Photoshop中的Adobe ACE CMM)，我得到的正是gs所看到的CMYK值，即[0.83，0.67，0.51，0.95].

If I take an RGB color of [0,0,0] in sRGB color space and convert it to the CMYK value defined by the PSO coated v3 ICC profile in Photoshop (using Adobe ACE CMM in Photoshop), I get exactly the CMYK values you are seeing with gs, that is [0.83, 0.67, 0.51, 0.95].

那是使用启用了黑点补偿的相对比色渲染意图.这些是gs默认用于lcms的设置.

That was using a relative colorimetric rendering intent with black point compensation enabled. Those are the settings that gs would be using for lcms by default.

我怀疑当您使用libcms2时，它使用的是不同的呈现意图.例如，当我将感知渲染意图与Adobe ACE一起使用时，我会得到[0.90，0.64，0.45，0.96].

I suspect that when you use libcms2, it is using a different rendering intent. For example, when I use the perceptual rendering intent with Adobe ACE I get [0.90, 0.64, 0.45, 0.96].

请注意，您可以使用gs指定要使用的呈现意图 -dRenderIntent = 0/1/2/3.请参见 https://ghostscript.com/doc/current/Use.htm#ICC_color_parameters详细信息.

Note that you can specify with gs what rendering intent you want to use with -dRenderIntent=0/1/2/3 . See https://ghostscript.com/doc/current/Use.htm#ICC_color_parameters for details.

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