path: root/0003-Apply-subpixel-rendering-in-Cairo-Backend.patch

From 1fd38e9b4726d0db9a769176a6464d6a2ae83237 Mon Sep 17 00:00:00 2001
From: Paul Gideon Dann <pdgiddie@gmail.com>
Date: Tue, 9 Aug 2016 15:02:53 +0100
Subject: [PATCH 3/4] Apply subpixel rendering in Cairo Backend

Source:
https://github.com/zhou13/poppler-subpixel/blob/master/poppler/poppler-subpixel.patch
---
 glib/demo/render.c         | 25 ++++++++++++++++++++---
 glib/poppler-page.cc       | 10 ++++++++++
 glib/poppler-page.h        |  1 +
 poppler/CairoFontEngine.cc |  6 +++---
 poppler/CairoOutputDev.cc  | 24 ++++++++++++++++++++++
 poppler/Gfx.cc             | 41 ++++++++++++++++++++++++++++++++++++++
 poppler/Gfx.h              |  3 +++
 poppler/Page.cc            | 13 ++++++++++++
 poppler/Page.h             |  3 +++
 9 files changed, 120 insertions(+), 6 deletions(-)

diff --git a/glib/demo/render.c b/glib/demo/render.c
index 78d24bb5..d482ceb5 100644
--- a/glib/demo/render.c
+++ b/glib/demo/render.c
@@ -82,12 +82,14 @@ pgd_render_start (GtkButton     *button,
 		  PgdRenderDemo *demo)
 {
 	PopplerPage *page;
+	gboolean     subpixel_rendering;
 	gdouble      page_width, page_height;
 	gdouble      width, height;
 	gint         x, y;
 	gchar       *str;
 	GTimer      *timer;
         cairo_t     *cr;
+        cairo_font_options_t *fo;
 
 	page = poppler_document_get_page (demo->doc, demo->page);
 	if (!page)
@@ -116,6 +118,21 @@ pgd_render_start (GtkButton     *button,
                                                     width, height);
         cr = cairo_create (demo->surface);
 
+        fo = cairo_font_options_create ();
+        cairo_get_font_options (cr, fo);
+
+        subpixel_rendering = poppler_page_support_subpixel_rendering (page);
+        printf("subpixel_rendering %d\n", subpixel_rendering);
+        if (subpixel_rendering) {
+                cairo_set_source_rgb (cr, 1., 1., 1.);
+                cairo_paint (cr);
+                cairo_font_options_set_antialias (fo, CAIRO_ANTIALIAS_SUBPIXEL);
+                cairo_font_options_set_subpixel_order (fo, CAIRO_SUBPIXEL_ORDER_RGB);
+        }
+
+        cairo_set_font_options (cr, fo);
+        cairo_font_options_destroy (fo);
+
         cairo_save (cr);
         switch (demo->rotate) {
         case 90:
@@ -143,9 +160,11 @@ pgd_render_start (GtkButton     *button,
                 poppler_page_render (page, cr);
         cairo_restore (cr);
 
-        cairo_set_operator (cr, CAIRO_OPERATOR_DEST_OVER);
-        cairo_set_source_rgb (cr, 1., 1., 1.);
-        cairo_paint (cr);
+        if (!subpixel_rendering) {
+                cairo_set_operator (cr, CAIRO_OPERATOR_DEST_OVER);
+                cairo_set_source_rgb (cr, 1., 1., 1.);
+                cairo_paint (cr);
+        }
 
         g_timer_stop (timer);
 
diff --git a/glib/poppler-page.cc b/glib/poppler-page.cc
index 8b5b4da0..709b760e 100644
--- a/glib/poppler-page.cc
+++ b/glib/poppler-page.cc
@@ -2447,3 +2447,13 @@ poppler_page_get_text_attributes_for_area (PopplerPage      *page,
 
   return g_list_reverse(attributes);
 }
+
+gboolean
+poppler_page_support_subpixel_rendering (PopplerPage        *page)
+{
+  CairoOutputDev *output_dev;
+  g_return_val_if_fail (POPPLER_IS_PAGE (page), FALSE);
+
+  output_dev = page->document->output_dev;
+  return page->page->supportSubpixelRendering(output_dev);
+}
diff --git a/glib/poppler-page.h b/glib/poppler-page.h
index f99f0920..8ff914f4 100644
--- a/glib/poppler-page.h
+++ b/glib/poppler-page.h
@@ -147,6 +147,7 @@ void                   poppler_page_free_text_attributes (GList              *li
 POPPLER_PUBLIC
 GList *        poppler_page_get_text_attributes_for_area (PopplerPage        *page,
                                                           PopplerRectangle   *area);
+gboolean         poppler_page_support_subpixel_rendering (PopplerPage        *page);
 
 /* A rectangle on a page, with coordinates in PDF points. */
 #define POPPLER_TYPE_RECTANGLE             (poppler_rectangle_get_type ())
diff --git a/poppler/CairoFontEngine.cc b/poppler/CairoFontEngine.cc
index bf6bd88d..d9e42304 100644
--- a/poppler/CairoFontEngine.cc
+++ b/poppler/CairoFontEngine.cc
@@ -124,7 +124,7 @@ CairoFont::getSubstitutionCorrection(GfxFont *gfxFont)
 	cairo_matrix_t m;
 	cairo_matrix_init_identity(&m);
 	cairo_font_options_t *options = cairo_font_options_create();
-	cairo_font_options_set_hint_style(options, CAIRO_HINT_STYLE_NONE);
+	cairo_font_options_set_hint_style(options, CAIRO_HINT_STYLE_SLIGHT);
 	cairo_font_options_set_hint_metrics(options, CAIRO_HINT_METRICS_OFF);
 	cairo_scaled_font_t *scaled_font = cairo_scaled_font_create(cairo_font_face, &m, &m, options);
 
@@ -182,7 +182,7 @@ _ft_new_face_uncached (FT_Library lib,
   }
 
   font_face = cairo_ft_font_face_create_for_ft_face (face,
-							  FT_LOAD_NO_HINTING |
+							  FT_LOAD_TARGET_LIGHT |
 							  FT_LOAD_NO_BITMAP);
   if (cairo_font_face_set_user_data (font_face,
 				     &_ft_cairo_key,
@@ -351,7 +351,7 @@ _ft_new_face (FT_Library lib,
   _ft_open_faces = l;
 
   l->font_face = cairo_ft_font_face_create_for_ft_face (tmpl.face,
-							  FT_LOAD_NO_HINTING |
+							  FT_LOAD_TARGET_LIGHT |
 							  FT_LOAD_NO_BITMAP);
   if (cairo_font_face_set_user_data (l->font_face,
 				     &_ft_cairo_key,
diff --git a/poppler/CairoOutputDev.cc b/poppler/CairoOutputDev.cc
index 68927636..c21229a7 100644
--- a/poppler/CairoOutputDev.cc
+++ b/poppler/CairoOutputDev.cc
@@ -205,6 +205,13 @@ void CairoOutputDev::setCairo(cairo_t *c)
   }
   if (c != nullptr) {
     cairo = cairo_reference (c);
+    {
+      cairo_font_options_t *options = cairo_font_options_create ();
+      cairo_get_font_options (cairo, options);
+      cairo_font_options_set_antialias (options, CAIRO_ANTIALIAS_SUBPIXEL);
+      cairo_set_font_options (cairo, options);
+      cairo_font_options_destroy (options);
+    }
 	/* save the initial matrix so that we can use it for type3 fonts. */
 	//XXX: is this sufficient? could we miss changes to the matrix somehow?
 	cairo_get_matrix(cairo, &orig_matrix);
@@ -1431,6 +1438,7 @@ void CairoOutputDev::drawChar(GfxState *state, double x, double y,
 void CairoOutputDev::endString(GfxState *state)
 {
   int render;
+  GfxFontType fontType;
 
   if (!currentFont)
     return;
@@ -1448,6 +1456,18 @@ void CairoOutputDev::endString(GfxState *state)
     goto finish;
   }
 
+  fontType = state->getFont()->getType();
+  // Do not enable subpixel rendering for type3 font
+  // For some reason it does not work
+  if (fontType == fontType3) {
+      cairo_save(cairo);
+      cairo_font_options_t *fo;
+      fo = cairo_font_options_create ();
+      cairo_get_font_options (cairo, fo);
+      cairo_font_options_set_antialias (fo, CAIRO_ANTIALIAS_DEFAULT);
+      cairo_set_font_options (cairo, fo);
+  }
+
   if (!(render & 1)) {
     LOG (printf ("fill string\n"));
     cairo_set_source (cairo, fill_pattern);
@@ -1498,6 +1518,10 @@ void CairoOutputDev::endString(GfxState *state)
   }
 
 finish:
+  // pair with the previous cairo_save to disable subpixel rendering for type3 fonts
+  if (fontType == fontType3) {
+      cairo_restore(cairo);
+  }
   gfree (glyphs);
   glyphs = nullptr;
   if (use_show_text_glyphs) {
diff --git a/poppler/Gfx.cc b/poppler/Gfx.cc
index a9b93b61..c84a09d5 100644
--- a/poppler/Gfx.cc
+++ b/poppler/Gfx.cc
@@ -4610,6 +4610,47 @@ void Gfx::doImage(Object *ref, Stream *str, bool inlineImg) {
   error(errSyntaxError, getPos(), "Bad image parameters");
 }
 
+bool Gfx::checkNormalBlendModeOnly(Object *str) {
+  printf("check blender mode start\n");
+  Object args[maxArgs];
+  int numArgs;
+  bool onlyNormalBlendMode;
+  Parser myParser(xref, str, false);
+
+  numArgs = 0;
+  onlyNormalBlendMode = true;
+
+  Object obj = myParser.getObj();
+  while (!obj.isEOF()) {
+    if (obj.isCmd()) {
+      const char* cmd = obj.getCmd();
+
+      if (strcmp(cmd, "gs") == 0) {
+        GfxBlendMode mode;
+        Object obj1 = res->lookupGState(args[0].getName());
+        if (!obj1.isNull()) {
+          Object obj2 = obj1.dictLookup("BM");
+          if (!obj2.isNull()) {
+            if (state->parseBlendMode(&obj2, &mode)) {
+              printf("check blend mode: %d\n", mode);
+              onlyNormalBlendMode &= (mode == gfxBlendNormal);
+            }
+          }
+        }
+      }
+
+      numArgs = 0;
+    } else if (numArgs < maxArgs) {
+      args[numArgs++] = obj.copy();
+    }
+
+    obj = myParser.getObj();
+  }
+
+  return onlyNormalBlendMode;
+}
+
+
 bool Gfx::checkTransparencyGroup(Dict *resDict) {
   // check the effect of compositing objects as a group:
   // look for ExtGState entries with ca != 1 or CA != 1 or BM != normal
diff --git a/poppler/Gfx.h b/poppler/Gfx.h
index 19462e8d..b0bbd11c 100644
--- a/poppler/Gfx.h
+++ b/poppler/Gfx.h
@@ -192,6 +192,9 @@ public:
   // Get the current graphics state object.
   GfxState *getState() { return state; }
 
+  // Check whether a stream only contains normal blend mode (to enable subpixel rendering)
+  bool checkNormalBlendModeOnly(Object *str);
+
   bool checkTransparencyGroup(Dict *resDict);
 
   void drawForm(Object *str, Dict *resDict, const double *matrix, const double *bbox,
diff --git a/poppler/Page.cc b/poppler/Page.cc
index d137ec4b..5950b964 100644
--- a/poppler/Page.cc
+++ b/poppler/Page.cc
@@ -336,6 +336,19 @@ Dict *Page::getResourceDictCopy(XRef *xrefA) {
   return dict ? dict->copy(xrefA) : nullptr;
 }
 
+bool Page::supportSubpixelRendering(OutputDev *out) {
+  bool supported = false;
+  PDFRectangle box;
+
+  Object obj = contents.fetch(xref);
+  if (!obj.isNull()) {
+    Gfx gfx(doc, out, attrs->getResourceDict(), &box, nullptr);
+    supported = gfx.checkNormalBlendModeOnly(&obj);
+  }
+
+  return supported;
+}
+
 void Page::replaceXRef(XRef *xrefA) {
   Object obj1;
   Dict *pageDict = pageObj.getDict()->copy(xrefA);
diff --git a/poppler/Page.h b/poppler/Page.h
index 01f056f9..d6547a79 100644
--- a/poppler/Page.h
+++ b/poppler/Page.h
@@ -183,6 +183,9 @@ public:
   Object *getResourceDictObject();
   Dict *getResourceDictCopy(XRef *xrefA);
 
+  // Whether the content in this page supports subpixel rendering (lcdfilter)
+  bool supportSubpixelRendering(OutputDev *out);
+
   // Get annotations array.
   Object getAnnotsObject(XRef *xrefA = nullptr) { return annotsObj.fetch(xrefA ? xrefA : xref); }
   // Add a new annotation to the page
-- 
2.22.0