libcupsfilters: Added gray PCLm support to ghostscript()

PCLm does not only support 24-bit sRGB bur also 8-bit sGray. All PCLm
printers, regardless of whether they are color or monochrome accept
these two color spaces. Monochrome printers have to convert color into
gray if needed.

Ghhostscript has a grayscale PCLm output device, "pclm8" since version
9.56.0. We now make use of it if the job is monochrome. This also
allows us to supply the cortrecr sGray ICC profile instead of the sRGB
one.

diff --git a/cupsfilters/ghostscript.c b/cupsfilters/ghostscript.c
index baed09317403bd102730114be766faa1553169d8..4f05b8841318633a0279a2ef1a165e91b6f87861 100644 (file)
--- a/cupsfilters/ghostscript.c
+++ b/cupsfilters/ghostscript.c
@@ -1192,7 +1192,10 @@ cfFilterGhostscript(int inputfd,            /* I - File descriptor input
 
       /* Ghostscript output device */
 
-      cupsArrayAdd(gs_args, strdup("-sDEVICE=pclm"));
+      if (h.cupsColorSpace == CUPS_CSPACE_SW)
+       cupsArrayAdd(gs_args, strdup("-sDEVICE=pclm8"));
+      else
+       cupsArrayAdd(gs_args, strdup("-sDEVICE=pclm"));
 
       /* Strip/Band Height */
 
@@ -1424,18 +1427,9 @@ cfFilterGhostscript(int inputfd,            /* I - File descriptor input
   } else if (!cm_disabled &&
             outformat == CF_FILTER_OUT_FORMAT_PCLM) {
     /* Set standard output ICC profile sGray/sRGB */
-    /*if (h.cupsColorSpace == CUPS_CSPACE_SW)
+    if (h.cupsColorSpace == CUPS_CSPACE_SW)
       cupsArrayAdd(gs_args, strdup("-sOutputICCProfile=sgray.icc"));
-      else if (h.cupsColorSpace == CUPS_CSPACE_SRGB)*/
-    /* Note that Ghostscript can only output PCLm with its "pclm" device
-       in 8-bit sRGB, not in grayscale, so we always use the sRGB color
-       profile for now.
-       It is not possible to convert to grayscale by applying the gray
-       color profile on GhostScript's "pclm" device, see
-       https://bugs.ghostscript.com/show_bug.cgi?id=705014
-       We eill need an additional output device, like "pclm8", if we
-       want grayscale PCLM output, see
-       https://bugs.ghostscript.com/show_bug.cgi?id=705035 */
+    else if (h.cupsColorSpace == CUPS_CSPACE_SRGB)
       cupsArrayAdd(gs_args, strdup("-sOutputICCProfile=srgb.icc"));
   }
   else if (!cm_disabled)