Improved overprint (simulation) control.

First, we add an fz_page_overprint function to detect if a
page uses overprint. Only PDF implements this currently (other
formats all return false). PDF looks for '/OP true' in any
ExtGState entry.

We make Mutool check this. If it finds it, and spot rendering
is not completely disabled, then it ensures that the separation
object passed to the pixmap into which we draw is non NULL. This
causes the draw device to do overprint simulation.

We ensure that mutool draw defaults to having the spot rendering
mode default to simulation in builds that support it.

Finally, we ensure that if an output intent is set by the document,
and spot rendering is not completely disabled, then we ensure the
seps object is non NULL so that we render to a group in the
specified output intent, and THEN convert down to the required
colorspace for the output.

This should make us match acrobats behaviour.

3 files changed, 23 insertions, 2 deletions

diff --git a/include/mupdf/fitz/document.h b/include/mupdf/fitz/document.h
index d3b9abd5..95e59632 100644
--- a/include/mupdf/fitz/document.h
+++ b/include/mupdf/fitz/document.h
@@ -178,6 +178,12 @@ typedef int (fz_page_separation_disabled_fn)(fz_context *ctx, fz_page *page, int
 */
 typedef fz_separations *(fz_page_separations_fn)(fz_context *ctx, fz_page *page);
 
+/*
+	fz_page_uses_overprint_fn: Type for a function to retrieve
+	whether or not a given page uses overprint.
+*/
+typedef int (fz_page_uses_overprint_fn)(fz_context *ctx, fz_page *page);
+
 typedef void (fz_annot_drop_fn)(fz_context *ctx, fz_annot *annot);
 typedef fz_annot *(fz_annot_next_fn)(fz_context *ctx, fz_annot *annot);
 typedef fz_rect *(fz_annot_bound_fn)(fz_context *ctx, fz_annot *annot, fz_rect *rect);
@@ -212,6 +218,7 @@ struct fz_page_s
 	fz_page_control_separation_fn *control_separation;
 	fz_page_separation_disabled_fn *separation_disabled;
 	fz_page_separations_fn *separations;
+	fz_page_uses_overprint_fn *overprint;
 };
 
 /*
@@ -610,6 +617,12 @@ fz_colorspace *fz_document_output_intent(fz_context *ctx, fz_document *doc);
 fz_separations *fz_page_separations(fz_context *ctx, fz_page *page);
 
 /*
+	fz_page_uses_overprint: Find out whether a given page requests
+	overprint.
+*/
+int fz_page_uses_overprint(fz_context *ctx, fz_page *page);
+
+/*
 	fz_save_gproof: Given a currently open document, create a
 	gproof skeleton file from that document.
 
diff --git a/include/mupdf/pdf/object.h b/include/mupdf/pdf/object.h
index 5ceab1f0..285acf4d 100644
--- a/include/mupdf/pdf/object.h
+++ b/include/mupdf/pdf/object.h
@@ -66,8 +66,15 @@ void pdf_unmark_obj(fz_context *ctx, pdf_obj *obj);
 /* obj memo functions - allows us to secretly remember "a memo" (a bool) in
  * an object, and to read back whether there was a memo, and if so, what it
  * was. */
-void pdf_set_obj_memo(fz_context *ctx, pdf_obj *obj, int memo);
-int pdf_obj_memo(fz_context *ctx, pdf_obj *obj, int *memo);
+
+enum
+{
+	PDF_FLAGS_MEMO_BM = 0,
+	PDF_FLAGS_MEMO_OP = 1
+};
+
+void pdf_set_obj_memo(fz_context *ctx, pdf_obj *obj, int bit, int memo);
+int pdf_obj_memo(fz_context *ctx, pdf_obj *obj, int bit, int *memo);
 
 /* obj dirty bit support. */
 int pdf_obj_is_dirty(fz_context *ctx, pdf_obj *obj);
diff --git a/include/mupdf/pdf/page.h b/include/mupdf/pdf/page.h
index 13f61bfa..969aedf0 100644
--- a/include/mupdf/pdf/page.h
+++ b/include/mupdf/pdf/page.h
@@ -194,6 +194,7 @@ struct pdf_page_s
 	pdf_obj *obj;
 
 	int transparency;
+	int overprint;
 	int incomplete;
 
 	fz_link *links;