pdfwrite - change the example PDF/A and PDF/X scripts

From Bug #700930 "Typo in example command for PDF/X-3 in VectorDevices.htm"

The reporter claimed that the (mis-spelled) command didn't work, which
was not surprising, since it contained a typo. After fixing the
documentation the reporter claimed that the command didn't work. This
is true and was missed because of the misleading title.

The PDFX_def.ps file was mistakenly pulling the ProcessColorModel from
systemdict, which would only be set if this was set on the command line.
The real problem is the fact that our setpagedevice/currentpagedevice
code doesn't truly reflect the device setup, so changes to the
ProcessColorModel caused by setting ColorConversionStrategy are not
reflected in the values returned by currentpagedevice.

This commit updates PDFX_def.ps to chaeck the ColorConversionStrategy
instead, which is more reliable, and then use the ProcessColorModel
from the currentpagedevice as a fallback if ColorConversionStrategy
is not set. (actually this should not be possible)

Update PDFA_def.ps similarly; although it was using the currentpagedvice
this is not a reliable method.

Finally; reformat the files, add some extra comments describing what the
code is doing, make it clearer that these files *should* be customised
and add additional some basic instruction on customising them.

2 files changed, 129 insertions, 29 deletions

diff --git a/lib/PDFA_def.ps b/lib/PDFA_def.ps
index f0ff0d1b6..f77c90ef1 100644
--- a/lib/PDFA_def.ps
+++ b/lib/PDFA_def.ps
@@ -1,30 +1,69 @@
 %!
 % This is a sample prefix file for creating a PDF/A document.
-% Feel free to modify entries marked with "Customize".
-% This assumes an ICC profile to reside in the file (ISO Coated sb.icc),
-% unless the user modifies the corresponding line below.
+% Users should modify entries marked with "Customize".
+% This assumes an ICC profile resides in the file (srgb.icc),
+% in the current directory unless the user modifies the corresponding line below.
 
 % Define entries in the document Info dictionary :
-/ICCProfile (srgb.icc) % Customise
-def
-
 [ /Title (Title)       % Customise
   /DOCINFO pdfmark
 
 % Define an ICC profile :
+/ICCProfile (srgb.icc) % Customise
+def
 
 [/_objdef {icc_PDFA} /type /stream /OBJ pdfmark
+
+%% This code attempts to set the /N (number of components) key for the ICC colour space.
+%% To do this it checks the ColorConversionStrategy or the device ProcessColorModel if
+%% ColorConversionStrategy is not set.
+%% This is not 100% reliable. A better solution is for the user to edit this and replace
+%% the code between the ---8<--- lines with a simple declaration like:
+%%   /N 3
+%% where the value of N is the number of components from the profile defined in /ICCProfile above.
+%%
 [{icc_PDFA}
 <<
-  /N currentpagedevice /ProcessColorModel known {
-    currentpagedevice /ProcessColorModel get dup /DeviceGray eq
-    {pop 1} {
-      /DeviceRGB eq
-      {3}{4} ifelse
+%% ----------8<--------------8<-------------8<--------------8<----------
+  systemdict /ColorConversionStrategy known {
+    systemdict /ColorConversionStrategy get cvn dup /Gray eq {
+      pop /N 1 false
+    }{
+      dup /RGB eq {
+        pop /N 3 false
+      }{
+        /CMYK eq {
+          /N 4 false
+        }{
+          (ColorConversionStrategy not a device space, falling back to ProcessColorModel, output may not be valid PDF/A.)=
+          true
+        } ifelse
+      } ifelse
     } ifelse
   } {
-    (ERROR, unable to determine ProcessColorModel) == flush
+    (ColorConversionStrategy not set, falling back to ProcessColorModel, output may not be valid PDF/A.)=
+    true
   } ifelse
+
+  {
+    currentpagedevice /ProcessColorModel get
+    dup /DeviceGray eq {
+      pop /N 1
+    }{
+      dup /DeviceRGB eq {
+        pop /N 3
+      }{
+        dup /DeviceCMYK eq {
+          pop /N 4
+        } {
+          (ProcessColorModel not a device space.)=
+          /ProcessColorModel cvx /rangecheck signalerror
+        } ifelse
+      } ifelse
+    } ifelse
+  } if
+%% ----------8<--------------8<-------------8<--------------8<----------
+
 >> /PUT pdfmark
 [{icc_PDFA} ICCProfile (r) file /PUT pdfmark
 
@@ -32,9 +71,9 @@ def
 
 [/_objdef {OutputIntent_PDFA} /type /dict /OBJ pdfmark
 [{OutputIntent_PDFA} <<
-  /Type /OutputIntent             % Must be so (the standard requires).
-  /S /GTS_PDFA1                   % Must be so (the standard requires).
-  /DestOutputProfile {icc_PDFA}            % Must be so (see above).
-  /OutputConditionIdentifier (sRGB)      % Customize
+  /Type /OutputIntent               % Must be so (the standard requires).
+  /S /GTS_PDFA1                     % Must be so (the standard requires).
+  /DestOutputProfile {icc_PDFA}     % Must be so (see above).
+  /OutputConditionIdentifier (sRGB) % Customize
 >> /PUT pdfmark
 [{Catalog} <</OutputIntents [ {OutputIntent_PDFA} ]>> /PUT pdfmark
diff --git a/lib/PDFX_def.ps b/lib/PDFX_def.ps
index 9ff233873..c251a82db 100644
--- a/lib/PDFX_def.ps
+++ b/lib/PDFX_def.ps
@@ -1,33 +1,94 @@
 %!
 % This is a sample prefix file for creating a PDF/X-3 document.
-% Feel free to modify entries marked with "Customize".
+% Users should modify entries marked with "Customize".
+% This assumes an ICC profile resides in the file (ISO Coated sb.icc)
+% in the current directory unless the user modifies the corresponding line below.
 
-% This assumes an ICC profile to reside in the file (ISO Coated sb.icc),
-% unless the user modifies the corresponding line below.
-
-systemdict /ProcessColorModel known {
-  systemdict /ProcessColorModel get dup /DeviceGray ne exch /DeviceCMYK ne and
+% First up, attempt to ensure the user has set ColorConversionStrategy correctly.
+% PDF/X-3 only permits Gray or CMYK in the output.
+%
+systemdict /ColorConversionStrategy known {
+  systemdict /ColorConversionStrategy get cvn dup /Gray ne exch /CMYK ne and
 } {
+  (\nERROR: ColorConversionStrategy not set.)=
   true
 } ifelse
-{ (ERROR: ProcessColorModel must be /DeviceGray or /DeviceCMYK.)=
-  /ProcessColorModel cvx /rangecheck signalerror
+{ (ERROR: ColorConversionStrategy must be /DeviceGray or /DeviceCMYK.)=
+  /ColorConversionStrategy cvx /rangecheck signalerror
 } if
 
-% Define entries to the document Info dictionary :
+{
+  (ColorConversionStrategy must be set and be either Gray or CMYK for PDF/X-3 output.)=
+  /ColorConversionStrategy cvx /rangecheck signalerror
+}if
 
-/ICCProfile (ISO Coated sb.icc) def  % Customize or remove.
 
+% Define entries in the document Info dictionary :
+%
 [ /GTS_PDFXVersion (PDF/X-3:2002) % Must be so (the standard requires).
   /Title (Title)                  % Customize.
   /Trapped /False                 % Must be so (Ghostscript doesn't provide other).
-  /DOCINFO pdfmark
+/DOCINFO pdfmark
 
-% Define an ICC profile :
 
+/ICCProfile (ISO Coated sb.icc) def  % Customize or remove.
+
+% Define an ICC profile in the output, if the user specified one.
+%
 currentdict /ICCProfile known {
   [/_objdef {icc_PDFX} /type /stream /OBJ pdfmark
-  [{icc_PDFX} <</N systemdict /ProcessColorModel get /DeviceGray eq {1} {4} ifelse >> /PUT pdfmark
+
+% This code attempts to set the /N (number of components) key for the ICC colour space.
+% To do this it checks the ColorConversionStrategy or the device ProcessColorModel if
+% ColorConversionStrategy is not set.
+% This is not 100% reliable. A better solution is for the user to edit this and replace
+% the code between the ---8<--- lines with a simple declaration like:
+%   /N 3
+% where the value of N is the number of components from the profile defined in /ICCProfile above.
+% Note, if you don't set ColorConversionStrategy, the output will likely be invalid anyway.
+  [{icc_PDFX} <<
+% ----------8<--------------8<-------------8<--------------8<----------
+  systemdict /ColorConversionStrategy known {
+    systemdict /ColorConversionStrategy get cvn dup /Gray eq {
+      pop /N 1 false
+    }{
+      dup /RGB eq {
+        (RGB is not a valid ColorConversionStrategy for PDF/X output)=
+        /ColorConversionStrategycvx /rangecheck signalerror
+      }{
+        /CMYK eq {
+          /N 4 false
+        }{
+          (ColorConversionStrategy not a device space, falling back to ProcessColorModel, output may not be valid PDF/X.)=
+          true
+        } ifelse
+      } ifelse
+    } ifelse
+  } {
+    (ColorConversionStrategy not set, falling back to ProcessColorModel, output may not be valid PDF/X.)=
+    true
+  } ifelse
+
+  {
+    currentpagedevice /ProcessColorModel get
+    dup /DeviceGray eq {
+      pop /N 1
+    }{
+      dup /DeviceRGB eq {
+        (RGB is not a valid ProcessColorModel for PDF/X output)=
+        /ColorConversionStrategycvx /rangecheck signalerror
+      }{
+        dup /DeviceCMYK eq {
+          pop /N 4
+        } {
+          (ProcessColorModel not a device space.)=
+          /ProcessColorModel cvx /rangecheck signalerror
+        } ifelse
+      } ifelse
+    } ifelse
+  } if
+% ----------8<--------------8<-------------8<--------------8<----------
+  >> /PUT pdfmark
   [{icc_PDFX} ICCProfile (r) file /PUT pdfmark
 } if