libppd remaps print-color-mode=bi-level, no 1-bit PWG output possible

Describe the bug

If the printer reports support for 1-bit bi-level raster (print-color-mode=bi-level, pwg-raster-document-type=black_1), libppd will remap -o print-color-mode=bi-level to =monochrome, because the ippeve generator uses ColorModel=FastGray for 1-bit output, but libppd remaps FastGray to print-color-mode=monochrome instead of =bi-level.

libppd/ppd/ppd-cache.c

Lines 386 to 395 in 4afdca9

    
            if ((choice = ppdFindMarkedChoice(ppd, "ColorModel")) != NULL) 
        
            { 
        
              // 
        
              // ColorModel is taken from PPD as its default option. 
        
              // 
        
              if (!strcmp(choice->choice, "Gray") || 
        
           !strcmp(choice->choice, "FastGray") || 
        
           !strcmp(choice->choice, "DeviceGray")) 
        
                keyword = "monochrome";

To Reproduce

PPD file has:

*cupsFilter2: "image/pwg-raster image/pwg-raster 100 -"
*OpenUI *ColorModel: PickOne
*OrderDependency: 10 AnySetup *ColorModel
*en_US.Translation ColorModel/Color Mode: ""
*ColorModel Gray: "<</cupsColorSpace 18/cupsBitsPerColor 8/cupsColorOrder 0/cupsCompression 0>>setpagedevice"
*ColorModel FastGray: "<</cupsColorSpace 3/cupsBitsPerColor 1/cupsColorOrder 0/cupsCompression 0>>setpagedevice"
*en_US.ColorModel Gray/Grayscale: ""
*DefaultColorModel: FastGray
*CloseUI: *ColorModel

I'm printing with: lp -d testp_l -o ColorModel=FastGray -o print-color-mode=bi-level -o page-ranges=1 document-a4.pdf

And the result:

D [22/Oct/2026:16:53:03 +0300] [Job 36] cfFilterGhostscript: Ghostscript command line: gs -dQUIET -dSAFER -dNOPAUSE -dBATCH -dNOINTERPOLATE -dNOMEDIAATTRS -dUsePDFX3Profile -sstdout=%stderr -sOutputFile=%stdout -sDEVICE=cups -sMediaClass=PwgRaster -sOutputType=automatic -r300x300 -dDEVICEWIDTHPOINTS=595 -dDEVICEHEIGHTPOINTS=842 -dcupsBitsPerColor=8 -dcupsColorOrder=0 -dcupsColorSpace=18 -dcupsBorderlessScalingFactor=0.0000 -dcupsInteger1=1 -dcupsInteger2=1 -scupsRenderingIntent=auto -scupsPageSizeName=A4 -dcupsManualCopies -I/usr/share/cups/fonts -sOutputICCProfile=sgray.icc -c -f -_

Second bug, in libcupsfilters: OpenPrinting/libcupsfilters#298

I'd like to fix this one. In ppdConvertOptions() (ppd-cache.c), FastGray always becomes "monochrome", so bi-level is never requested. I'll map it to bi-level when the printer supports it and add a test.

Keep in mind that the IPP printer might have black_1 in pwg-raster-document-type-supported only, but announce print-color-mode-supported=monochrome, without bi-level. That's also acceptable according to specification as far as I could see.

This means that CUPS, somehow, needs to generate 1-bit output even with print-color-mode=monochrome, if the printer has only pwg-raster-document-type=black_1.

But maybe that could be seen as another bug, and probably not in libppd.
Also see OpenPrinting/libcupsfilters#298

@ValdikSS

Keep in mind that the IPP printer might have black_1 in pwg-raster-document-type-supported only, but announce print-color-mode-supported=monochrome, without bi-level. That's also acceptable according to specification as far as I could see.

This means that CUPS, somehow, needs to generate 1-bit output even with print-color-mode=monochrome, if the printer has only pwg-raster-document-type=black_1.

But maybe that could be seen as another bug, and probably not in libppd. Also see OpenPrinting/libcupsfilters#298

Thanks @ValdikSS , that makes sense. I opened #106 for the bi-level case here. A printer with only black_1 that lists monochrome still gets monochrome; I left that for libcupsfilters #298 . I can look at that one next if nobody else is on it.

ppd-cache.c: Map FastGray to bi-level when the printer supports it

I'm not sure about closing this one too.

If I have a printer that reports print-color-mode-supported=bi-level, it still gets monochrome (PPD from driverless). This happens regardless of whether lp is run without arguments or with -o ColorModel=FastGray -o print-color-mode=bi-level.

If I pass only -o print-color-mode=bi-level to lp, something really strange happens:

bi-level+monochrome/black_1             colorMode=color    bpp=1 colorspace=3 # ??
bi-level+monochrome/sgray_1+black_8     colorMode=bi-level bpp=1 colorspace=18
bi-level/black_1                        colorMode=color    bpp=1 colorspace=3 # ??
monochrome+bi-level/black_1             colorMode=bi-level bpp=1 colorspace=3
monochrome/black_1                      colorMode=bi-level bpp=1 colorspace=3 # ??

Where bi-level+monochrome/sgray_1+black_8 means that the printer reports print-color-mode-supported=bi-level,monochrome (default: bi-level) and pwg-raster-document-type-supported=sgray_1,black_8 (default: sgray_1).

I'm not sure about closing this one too.

If I have a printer that reports print-color-mode-supported=bi-level, it still gets monochrome (PPD from driverless). This happens regardless of whether lp is run without arguments or with -o ColorModel=FastGray -o print-color-mode=bi-level.

If I pass only -o print-color-mode=bi-level to lp, something really strange happens:
bi-level+monochrome/black_1             colorMode=color    bpp=1 colorspace=3 # ??
bi-level+monochrome/sgray_1+black_8     colorMode=bi-level bpp=1 colorspace=18
bi-level/black_1                        colorMode=color    bpp=1 colorspace=3 # ??
monochrome+bi-level/black_1             colorMode=bi-level bpp=1 colorspace=3
monochrome/black_1                      colorMode=bi-level bpp=1 colorspace=3 # ??
Where bi-level+monochrome/sgray_1+black_8 means that the printer reports print-color-mode-supported=bi-level,monochrome (default: bi-level) and pwg-raster-document-type-supported=sgray_1,black_8 (default: sgray_1).

#106 fixed the mapping in libppd's ppdConvertOptions(), which is what the issue pointed to. What you see with lp comes from CUPS's own copy, _cupsConvertOptions() in cups/ppd-cache.c (used by backend/ipp.c), which still maps FastGray to monochrome. So the libppd fix is correct, but the same change is needed in OpenPrinting/cups for normal printing.

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libppd remaps print-color-mode=bi-level, no 1-bit PWG output possible #91

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	if ((choice = ppdFindMarkedChoice(ppd, "ColorModel")) != NULL)
	{
	//
	// ColorModel is taken from PPD as its default option.
	//

	if (!strcmp(choice->choice, "Gray") \|\|
	!strcmp(choice->choice, "FastGray") \|\|
	!strcmp(choice->choice, "DeviceGray"))
	keyword = "monochrome";

libppd remaps print-color-mode=bi-level, no 1-bit PWG output possible #91

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DSingh0304 commented on Nov 13, 2026

ValdikSS commented on Nov 13, 2026

DSingh0304 commented on Nov 13, 2026

darkvision77 commented on Nov 15, 2026

DSingh0304 commented on Nov 15, 2026

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