Bug fix: handle ColorSpace lookup for inline images (fixes #392)

If the value of /CS in the inline image dictionary was is key in the
page's /Resource -> /ColorSpace dictionary, properly resolve it by
referencing the proper colorspace, and not just the name, in the
external image dictionary.

ChangeLog

@@ -1,5 +1,9 @@
 2020-01-26  Jay Berkenbilt  <ejb@ql.org>
 
+	* Bug fix: when externalizing inline images, a colorspace value
+	that was a lookup key in the page's /Resource -> /ColorSpace
+	dictionary was not properly handled. Fixes #392.
+
 	* Add "encrypt" key to the json output. This contains largely the
 	same information as given by --show-encryption but in a
 	consistent, parseable format.

libqpdf/QPDFPageObjectHelper.cc

@@ -141,6 +141,22 @@ InlineImageTracker::convertIIDict(QPDFObjectHandle odict)
                 }
                 else
                 {
+                    // This is a key in the page's /Resources ->
+                    // /ColorSpace dictionary. We need to look it up
+                    // and use its value as the color space for the
+                    // image.
+                    QPDFObjectHandle colorspace =
+                        resources.getKey("/ColorSpace");
+                    if (colorspace.isDictionary() && colorspace.hasKey(name))
+                    {
+                        QTC::TC("qpdf", "QPDFPageObjectHelper colorspace lookup");
+                        value = colorspace.getKey(name);
+                    }
+                    else
+                    {
+                        resources.warnIfPossible(
+                            "unable to resolve colorspace " + name);
+                    }
                     name.clear();
                 }
                 if (! name.empty())

qpdf/qpdf.testcov

@@ -447,3 +447,4 @@ QPDF_encryption same password 1
 QPDFWriter stream in ostream 0
 QPDFObjectHandle duplicate dict key 0
 QPDFWriter no encryption sig contents 0
+QPDFPageObjectHelper colorspace lookup 0

qpdf/qtest/qpdf.test

@@ -809,7 +809,7 @@ $td->runtest("check pass1 file",
 show_ntests();
 # ----------
 $td->notify("--- Inline Images ---");
-$n_tests += 8;
+$n_tests += 10;
 
 # The file large-inline-image.pdf is a hand-crafted file with several
 # inline images of various sizes including one that is two megabytes,
@@ -853,6 +853,16 @@ $td->runtest("externalize damaged image",
 $td->runtest("check output",
 	     {$td->FILE => "a.pdf"},
 	     {$td->FILE => "damaged-inline-image-out.pdf"});
+$td->runtest("named colorspace",
+             {$td->COMMAND =>
+                  "qpdf --static-id --externalize-inline-images" .
+                  " --ii-min-bytes=0 inline-image-colorspace-lookup.pdf a.pdf"},
+             {$td->STRING => "", $td->EXIT_STATUS => 0},
+             $td->NORMALIZE_NEWLINES);
+$td->runtest("check output",
+	     {$td->FILE => "a.pdf"},
+	     {$td->FILE => "inline-image-colorspace-lookup-out.pdf"});
+
 
 my @eii_tests = (
     ['inline-images', 80],