diff-pdf-split.patch

diff --git a/diff-pdf.cpp b/diff-pdf.cpp
index abcdef1..1234567 100644
--- a/diff-pdf.cpp
+++ b/diff-pdf.cpp
@@
 bool g_verbose = false;
 bool g_skip_identical = false;
 bool g_mark_differences = false;
 long g_channel_tolerance = 0;
 long g_per_page_pixel_tolerance = 0;
 bool g_grayscale = false;
+bool g_split_output = false;

@@
     cairo_surface_t *diff =
-        cairo_image_surface_create(CAIRO_FORMAT_RGB24, rdiff.width, rdiff.height);
+        cairo_image_surface_create(CAIRO_FORMAT_RGB24, rdiff.width, rdiff.height);
+
+    cairo_surface_t *removed = NULL, *added = NULL;
+    if (removal_view)
+        removed = cairo_image_surface_create(CAIRO_FORMAT_RGB24, rdiff.width, rdiff.height);
+    if (addition_view)
+        added = cairo_image_surface_create(CAIRO_FORMAT_RGB24, rdiff.width, rdiff.height);
+    if (removed || added) {
+        if (removed) {
+            cairo_t *cr = cairo_create(removed);
+            cairo_set_source_rgb(cr, 1, 1, 1);
+            cairo_paint(cr);
+            cairo_destroy(cr);
+        }
+        if (added) {
+            cairo_t *cr = cairo_create(added);
+            cairo_set_source_rgb(cr, 1, 1, 1);
+            cairo_paint(cr);
+            cairo_destroy(cr);
+        }
+    }

@@
                 if ( cr1 > (cr2+g_channel_tolerance) || cr1 < (cr2-g_channel_tolerance)
                   || cg1 > (cg2+g_channel_tolerance) || cg1 < (cg2-g_channel_tolerance)
                   || cb1 > (cb2+g_channel_tolerance) || cb1 < (cb2-g_channel_tolerance)
                    )
                 {
                     pixel_diff_count++;
                     changes = true;
                     linediff = true;
+
+                    if (removed) {
+                        *(removed_row + x + 0) = cr1;
+                        *(removed_row + x + 1) = cg1;
+                        *(removed_row + x + 2) = cb1;
+                        *(removed_row + x + 3) = 0xff;
+                    }
+                    if (added) {
+                        *(added_row + x + 0) = cr2;
+                        *(added_row + x + 1) = cg2;
+                        *(added_row + x + 2) = cb2;
+                        *(added_row + x + 3) = 0xff;
+                    }
                 }

@@
     if ( g_per_page_pixel_tolerance == 0 ? changes : pixel_diff_count > g_per_page_pixel_tolerance)
     {
-        return diff;
+        if (removal_view) *removal_view = removed;
+        if (addition_view) *addition_view = added;
+        return diff;
     }
     else
     {
         cairo_surface_destroy(diff);
+        if (removed) cairo_surface_destroy(removed);
+        if (added) cairo_surface_destroy(added);
         return NULL;
     }
 }

@@
 bool page_compare(int page, cairo_t *cr_out,
                   PopplerPage *page1, PopplerPage *page2,
-                  wxImage *thumbnail = NULL, int thumbnail_width = -1)
+                  wxImage *thumbnail = NULL, int thumbnail_width = -1,
+                  cairo_t *split_cr = NULL)
 {
     cairo_surface_t *img1 = page1 ? render_page(page1) : NULL;
     cairo_surface_t *img2 = page2 ? render_page(page2) : NULL;

-    cairo_surface_t *diff = diff_images(page, img1, img2, 0, 0,
-                                        thumbnail, thumbnail_width);
+    cairo_surface_t *removed = NULL, *added = NULL;
+    cairo_surface_t *diff = diff_images(page, img1, img2, 0, 0,
+                                        thumbnail, thumbnail_width,
+                                        g_split_output ? &removed : NULL,
+                                        g_split_output ? &added : NULL);
     const bool has_diff = (diff != NULL);

     if ( cr_out )
     {
         ...
         if (diff || !g_skip_identical)
             cairo_show_page(cr_out);
     }

+    if (g_split_output && removed && added && split_cr)
+    {
+        for (cairo_surface_t *surf : { removed, added }) {
+            cairo_save(split_cr);
+            cairo_scale(split_cr, 72.0 / g_resolution, 72.0 / g_resolution);
+            cairo_set_source_surface(split_cr, surf, 0, 0);
+            cairo_paint(split_cr);
+            cairo_restore(split_cr);
+            cairo_show_page(split_cr);
+            cairo_surface_destroy(surf);
+        }
+    }

     ...
     return !has_diff;
 }

@@
 bool doc_compare(PopplerDocument *doc1, PopplerDocument *doc2,
                  const char *pdf_output,
                  std::vector<bool> *differences,
                  wxProgressDialog *progress = NULL,
                  Gutter *gutter = NULL)
 {
     int pages_differ = 0;
     ...
+    cairo_surface_t *split_surface_out = NULL;
+    cairo_t *split_cr_out = NULL;
+    wxString split_file;
+
+    if (g_split_output && pdf_output)
+    {
+        split_file = wxString(pdf_output) + "_split.pdf";
+        double w, h;
+        poppler_page_get_size(poppler_document_get_page(doc1, 0), &w, &h);
+        split_surface_out = cairo_pdf_surface_create(split_file.utf8_str(), w, h);
+        split_cr_out = cairo_create(split_surface_out);
+    }

@@
         if ( gutter )
         {
             ...
-            page_same = page_compare(page, cr_out, page1, page2,
-                                     &thumbnail, Gutter::WIDTH);
+            page_same = page_compare(page, cr_out, page1, page2,
+                                     &thumbnail, Gutter::WIDTH,
+                                     split_cr_out);
             ...
         }
         else
         {
-            page_same = page_compare(page, cr_out, page1, page2);
+            page_same = page_compare(page, cr_out, page1, page2, NULL, -1,
+                                     split_cr_out);
         }

@@
     if ( pdf_output )
     {
         cairo_destroy(cr_out);
         cairo_surface_destroy(surface_out);
     }
+
+    if (split_cr_out) {
+        cairo_destroy(split_cr_out);
+        cairo_surface_destroy(split_surface_out);
+    }

@@
     static const wxCmdLineEntryDesc cmd_line_desc[] =
     {
         ...
+        { wxCMD_LINE_SWITCH,
+                  NULL, "split", "add pages showing removed and added content separately" },

@@
     if ( parser.Found("grayscale") )
         g_grayscale = true;
+
+    if ( parser.Found("split") )
+        g_split_output = true;