[libdocument] Add a function to invert colors of an image cairo surface

[evince.git] / libdocument / ev-document-misc.c

diff --git a/libdocument/ev-document-misc.c b/libdocument/ev-document-misc.c
index ced1ca11cb30b256ef4ac8da8048fb67cddc6eec..14bc3a354a3d86cd122293499fecf7e1e91020b9 100644 (file)
--- a/libdocument/ev-document-misc.c
+++ b/libdocument/ev-document-misc.c
@@ -296,6 +296,44 @@ ev_document_misc_surface_rotate_and_scale (cairo_surface_t *surface,
        return new_surface;
 }
 
+void
+ev_document_misc_invert_surface (cairo_surface_t *surface) {
+#if CAIRO_VERSION > CAIRO_VERSION_ENCODE(1, 9, 2)
+       cairo_t *cr;
+
+       cr = cairo_create (surface);
+
+       /* white + DIFFERENCE -> invert */
+       cairo_set_operator (cr, CAIRO_OPERATOR_DIFFERENCE);
+       cairo_set_source_rgb (cr, 1., 1., 1.);
+       cairo_paint(cr);
+       cairo_destroy (cr);
+#else
+       guchar *data;
+       gint    rowstride;
+       gint    width, height;
+       gint    x, y;
+
+       data = cairo_image_surface_get_data (surface);
+       rowstride = cairo_image_surface_get_stride (surface);
+       width = cairo_image_surface_get_width (surface);
+       height = cairo_image_surface_get_height (surface);
+
+       for (y = 0; y < height; y++) {
+               guchar *p = data + y * rowstride;
+
+               for (x = 0; x < width; x++) {
+                       p[0] = 255 - p[0];
+                       p[1] = 255 - p[1];
+                       p[2] = 255 - p[2];
+                       p += 4;
+               }
+       }
+
+       cairo_surface_mark_dirty (surface);
+#endif
+}
+
 void
 ev_document_misc_invert_pixbuf (GdkPixbuf *pixbuf)
 {