I have a PDF with spot colors and need to convert to cmyk tif. When i use the tiff32nc device i get a black and white file but if i run tiffsep i get all the separates and the composite cmyk tif is correctly colored. I suspect it has something to do with the way that overprinting is set in the PDF. Does anyone know which of the many command line parameters are executed in process of creating the composite cmyk tiff vs the tiff32nc tiff?
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I'm trying to use Ghostscript to convert PDF files which have RGB colors into CMYK colors. The blue colors in my PDF get converted into DeviceCMYK just fine. However, pure white colors (i.e. RGB 255, 255, 255) don't show up in the CMYK separation when I do Output Preview in Adobe Acrobat. When I use Acrobat's Object Inspector, it reveals that my white colors have ColorSpace=DeviceGray and ColorValues=1.0 (i.e. white).
This is the simplest form of the command I'm using:
ghostscript\gswin32c.exe -sDEVICE=pdfwrite -dBATCH -dNOPAUSE -sColorConversionStrategy=CMYK -sOutputFile="cmyk.pdf" "rgb.pdf"
I would like to force these white colors to be ColorSpace=DeviceCMYK and ColorValues=0, 0, 0, 0. (This is what Acrobat's Convert Colors produces). How can I do that? I tried hunting through the documentation and trying out various switches that I didn't fully understand, but the result was always the same so far.
If it matters, the version of Ghostscript is 9.21
Input and output files can be downloaded here: https://ufile.io/f/faxbb
It's quite simple, you can't do that. The pdfwrite device regards DeviceGray as a subset of CMYK (it's the K channel) and if it finds a DeviceGray colour it will retain it as such. However, true RGB colours ought to be converted to CMYK.
You haven't supplied the original file so I can't inspect it or try it.
You should upgrade, 9.21 is 3 years old, 9.53.0 was released today.
Edit
I checked the code and this is actually an optimisation. C=M=Y=0, K=% or R=G=B are converted into DeviceGray when written out (ONLY if you are using ColorConversion though!). This is because a single component floating point is smaller to write than three floating point values, so you get a smaller PDF file.
If any profession printing service fails to print colours in DeviceGray I'd be shocked. I'd also be looking for a new printer!
I'm trying to convert an EPS file with an embedded TIFF that has a transparent background to a PNG using GhostScript. The problem that I am having is that the background of the TIFF image becomes white in the PNG. It looks like the following:
IncorrectPNG
When I export from Adobe Illustrator, it comes out correct:
CorrectPNG
I was reading that there is not transparency in EPS, only marked and unmarked areas. I was wondering if there was a call that I was missing that would create the PNG through Ghostscript similar to that of Illustrator? Or if there is any other alternative that doesn't just replace white with transparency through ImageMagick?
I am using Windows and have Ghostscript 9.25 installed. Here is the command (one of many) that I've tried:
-q -dQUIET -dSAFER -dBATCH -dNOPAUSE -dNOPROMPT -sDEVICE=pngalpha -r300 -dEPSCrop NamePlatePNG.png NamePlate.eps
I can get the EPS file to you if needed. Any help would be appreciated, thanks!
UPDATE:
Here is the EPS file (Hopefully this link works):
https://drive.google.com/open?id=1m4HHGLoPe0jdWkx1Oghe7ttiXPldZnJs
Also, I should have mentioned that the images I uploaded were just screenshots of the PNGs open in an image editor. The checkered portion is indeed fully transparent alpha channel. I was trying to easily accentuate the difference.
Your file doesn't look like its transparent, it looks like its masked, possibly with a stencil mask, possibly chroma-keyed. Without seeing the file I can't tell for sure.
You are correct that PostScript (and hence EPS) doesn't support transparency, but it does support several features which have somewhat similar effects.
The color space is irrelevant, and in fact the only kind of 'transparency' supported in PostScript works when the color space is CMYK, but not when its RGB (and certainly not sRGB, which isn't even a PostScript color space, you have to manufacture it from CIEBasedABC)
As far as I can see the command line you are using is correct, but as I say I can't tell much without seeing the actual EPS program.
[EDIT]
So the Ghostscript rendering is correct, that's what is in your EPS file, there is no transparency of any kind there. So how is Illustrator able to make a transparent PNG ? Well the answer is that Illustrator isn't using the PostScript part of the EPS file.
About 1/3 of the way through the EPS file you'll see a line which reads:
%AI9_PrivateDataBegin
What follows that is an Adobe Illustrator file format. When AI reads the file it finds that line, throws away the PostScript portion of the file, and reads the AI representation of the content from the portion of the file beginning with that comment.
Now stored somewhere in there will be the information that portions of the content are transparent. Although PostScript can't represent that, Illustrator's internal format can. So when you write a PNG file from Illustrator it knows that portion is transparent and writes it as such.
Ghostscript, however, is constrained by the PostScript portion of the file, it can't read the Illustrator native format, and so renders the image with a white background.
It 'might' be possible to save a different kind of EPS from Illustrator (level 3 instead of level 2 possibly, I notice this is a language level 2 EPS file) which duplicate the effect, but from what you have here, there isn't anything a standard PostScript interpreter can do which will give you the result you want.
I'm planning to use colorprofiles while converting pdf's to jpg/png/pdf(low res/high res/rgb/cmyk) but (Question 1)I could not find how could I determine if a input document has an icc profile and if it has do i use it to help my conversion. Is there a ghostscript command to determine icc profiles
I found a gs command to convert to pdf as below from link:
gs -o cmyk-doc.pdf \
-sDEVICE=pdfwrite \
-dOverrideICC=true \
-sDefaultCMYKProfi le=/path/to/mycmykprofi le.icc \
-sOutputICCProfi le=/path/to/mydevicepro file.icc \
-dRenderIntent=3 \
-dDeviceGrayToK=true \
input-doc.pdf
(Question 2)If my input document has a profile, can I skip the option -sDefaultCMYKProfi le and only pass the required -sOutputICCProfile.
You can't use Ghostscript to determine if a PDF file has ICC colour profiles. Note there can be numerous colour profiles in a PDF file. Each colour can be in its own space, and each space can use a different ICC colour profile. That's in addition to the OutputIntent profile. On the other hand, you don't need to care.
For rendering you are basically looking at a conversion like this:
input colour -> CIE representation -> output colour
The input colour (in PDF) can be Gray, RGB, CMYK, Separation, DeviceN or one of the CIE spaces; Lab, ICC.
The output colour, for rendering will need to be one of Gray, RGB, CMYK or 'separated' (where each component rendered to a separate gray image).
The OutputICCProfile controls the second half of that conversion, the Default* profiles control the first half of that conversion, when the colour space isn't already one of the CIE spaces.
Taking question 2 first....
You never need to supply the DefaultCMYKProfile. That is used to override the Ghostscript default CMYK->CIE profile. You can use this if you happen to know that the input file is in CMYK space, and that it was a characterised CMYK space. In which case supplying the profile for that space would do a better job of converting from CMYK to CIE than the Ghostscript default one. However this is rare and generally only true in controlled workflows.
For question 1:
You only really care if the PDF file does not contain ICC profiles but instead defines colours in a device space such as RGB or CMYK. In that case, and assuming the PDF file has been created for a colour controlled workflow, you might assume that all the colours are in the same space, in which case I believe you would want to use the OutputIntent profile from the PDF file, or override the Ghostscript default (see below). There is extensive documentation on the use of ICC profiles here.
The OutputICCProfile is used with rendering devices in order to characterise the output space. So if you are rendering to RGB output you might use a specific RGB ICC profile to convert from CIE space to RGB space. That profile might additionally then be attached to the output file (eg JPEG) and a conforming reader would be able to use that profile to convert the RGB samples back into CIE space in order to use yet another profile to convert to a different characterised space (eg the profile for your display).
Now that's for rendering, ie creating a bitmap image. The pdfwrite device, on the other hand, goes to considerable lengths to maintain input colours in their original colour space. If you want to convert them into a different space then you need to set -sColorConversionStrtaegy. The command line you've quoted won't do that. If you want it converted to a characterised CMYK space then you would indeed supply the OutputICCProfile, but you do need to specify -sColorConversionStrategy=DeviceCMYK.
I'm trying to convert preview pdfs uploaded by converting them to jpeg. Please can someone tell me how I can preview overprint? i.e. if a white object is set to overprint over a coloured background it shouldn't be shown - we only see the background.
/c 'C:\Program Files\gs\gs9.10\bin\gswin64c.exe' -o image%04d.jpg -sDEVICE=jpeg -dJPEGQ=60 -r150 -dSimulateOverprint=false -dUseCropBox uploaded.pdf
Also how can I output/list the created files?
Thanks
Overprint is only defined for CMYK inks, so you need to run to a device which support CMYK output. If you go to gray or RGB then the CMYK values are converted to RGB and will no longer overprint.
Try the tiff32nc device. Or jpegcmyk if you really want to use jpeg.
Is it possible to check if a PDF is CMYK or RGB using GhostScript?
I am aware of the inkcov feature, but this just returns values in terms of CMYK (with silent conversion)?
Is the real check, a check for RGB colours or RGB images within the PDF? not sure if both RGB and CMYK images can exist in the same PDF?
Images aren't the only thing that can be in a PDF file, you can also have text, linework and shadings. Also transparency blending can be specified in specific colour spaces. Colour spaces are not limited to RGB or CMYK but can also include Gray and spot (Separation) colours, as well as ICCBased colour spaces and certain specific CIE colour spaces such as Lab.
All of these colour spaces can potentially be present in a PDF file simultaneously.
Ghostscript doesn't contain any tools currently to tell you what colour spaces are used in a PDF file, though the pdf_info.ps script could be modified to do so for unusual (not grey/RGB/CMYK) spaces. You could also write a small piece of PostScript which could tell you when a colour space was used, and what kind of colour it is.
The inkcov device is a CMYK device, so all colours specified in the PDF are converted to CMYK before being 'printed' to the inkcov device which counts up the coverage. It doesn't tell you anything about the original PDF file.
My understanding is that a PDF can contain both RGB and CMYK images, so you'd need to have a tool that can review all images and report on their mode.
If GhostScript doesn't include options to do so, you may have to write a script to use a PDF library for parsing the image and reporting details on the elements it contains.
For example, this Cam::PDF module in Perl says it can parse any PDF v1.5 formatted file.