Re: patch for gdk-pixbuf to read and write PNG tEXt chunks



Hi,

following up to myself, here's a reworked patch. It features better cleanup
on error, adds the proposed "tEXt::" prefix to the gdk_pixbuf_save parameters
and to the gobject data and gives some info about the new PNG parameter in
the inline docs.

There is one issue that I'm still unsure about: When a wrong parameter is
passed to the PNG saver it gives a warning and returns FALSE without setting
GError. This leads to a segfault later. I've copied this code from the 
JPEG save routine, so if this is considered the wrong behaviour, we should
fix it in other places too. We'd probably need a new GDK_PIXBUF_ERROR value
then (GDK_PIXBUF_ERROR_BAD_OPTION ?!).


Salut, Sven


Index: gdk-pixbuf/gdk-pixbuf-io.c
===================================================================
RCS file: /cvs/gnome/gtk+/gdk-pixbuf/gdk-pixbuf-io.c,v
retrieving revision 1.60
diff -u -r1.60 gdk-pixbuf-io.c
--- gdk-pixbuf/gdk-pixbuf-io.c	2001/09/14 22:04:55	1.60
+++ gdk-pixbuf/gdk-pixbuf-io.c	2001/09/20 10:17:59
@@ -731,8 +731,8 @@
  * @Varargs: list of key-value save options
  *
  * Saves pixbuf to a file in @type, which is currently "jpeg" or
- * "png".  If @error is set, FALSE will be returned. Possible errors include those
- * in the #GDK_PIXBUF_ERROR domain and those in the #G_FILE_ERROR domain.
+ * "png".  If @error is set, FALSE will be returned. Possible errors include 
+ * those in the #GDK_PIXBUF_ERROR domain and those in the #G_FILE_ERROR domain.
  *
  * The variable argument list should be NULL-terminated; if not empty,
  * it should contain pairs of strings that modify the save
@@ -743,8 +743,11 @@
  *                  "quality", "100", NULL);
  * </programlisting>
  *
- * The only save parameter that currently exists is the "quality" field
- * for JPEG images; its value should be in the range [0,100].
+ * Currently only few parameters exist. JPEG images can be saved with a 
+ * "quality" parameter; its value should be in the range [0,100]. 
+ * Text chunks can be attached to PNG images by specifying parameters of
+ * the form "tEXt::key", where key is an ASCII string of length 1-79;
+ * the values being strings.
  *
  * Return value: whether an error was set
  **/
Index: gdk-pixbuf/io-png.c
===================================================================
RCS file: /cvs/gnome/gtk+/gdk-pixbuf/io-png.c,v
retrieving revision 1.41
diff -u -r1.41 io-png.c
--- gdk-pixbuf/io-png.c	2001/08/30 07:21:13	1.41
+++ gdk-pixbuf/io-png.c	2001/09/20 10:17:59
@@ -186,13 +186,17 @@
 static GdkPixbuf *
 gdk_pixbuf__png_image_load (FILE *f, GError **error)
 {
+        GdkPixbuf *pixbuf;
 	png_structp png_ptr;
 	png_infop info_ptr, end_info;
+        png_textp text_ptr;
         gboolean failed = FALSE;
 	gint i, ctype, bpp;
 	png_uint_32 w, h;
 	png_bytepp rows;
 	guchar *pixels;
+        gint    num_text = 0;
+        gchar **texts    = NULL;
 
 	png_ptr = png_create_read_struct (PNG_LIBPNG_VER_STRING,
                                           error,
@@ -255,17 +259,43 @@
 		rows[i] = pixels + i * w * bpp;
 
 	png_read_image (png_ptr, rows);
+
+        if (png_get_text (png_ptr, info_ptr, &text_ptr, &num_text)) {
+                texts = g_new (gchar*, 2 * num_text);
+                for (i = 0; i < num_text; i++) {
+                        texts[2*i]   = g_strconcat ("tEXt::", text_ptr[i].key, NULL);
+                        texts[2*i+1] = g_strdup (text_ptr[i].text);
+                }
+        }
+
 	png_destroy_read_struct (&png_ptr, &info_ptr, &end_info);
 	g_free (rows);
 
 	if (ctype & PNG_COLOR_MASK_ALPHA)
-		return gdk_pixbuf_new_from_data (pixels, GDK_COLORSPACE_RGB, TRUE, 8,
-						 w, h, w * 4,
-						 free_buffer, NULL);
+		pixbuf = gdk_pixbuf_new_from_data (pixels, GDK_COLORSPACE_RGB, TRUE, 8,
+                                                   w, h, w * 4,
+                                                   free_buffer, NULL);
 	else
-		return gdk_pixbuf_new_from_data (pixels, GDK_COLORSPACE_RGB, FALSE, 8,
-						 w, h, w * 3,
-						 free_buffer, NULL);
+		pixbuf = gdk_pixbuf_new_from_data (pixels, GDK_COLORSPACE_RGB, FALSE, 8,
+                                                   w, h, w * 3,
+                                                   free_buffer, NULL);
+
+        /* Attach tEXt chunks as object data */
+
+        if (pixbuf) {
+                for (i = 0; i < num_text; i++) {
+                        g_object_set_data_full (G_OBJECT (pixbuf), 
+                                                texts[2*i], texts[2*i+1],
+                                                (GDestroyNotify) g_free);
+                        g_free (texts[2*i]);
+                }
+        } else {
+                for (i = 0; i < 2*num_text; i++)
+                        g_free (texts[i]);
+        }
+        g_free (texts);
+
+        return pixbuf;
 }
 
 /* I wish these avoided the setjmp()/longjmp() crap in libpng instead
@@ -501,7 +531,10 @@
 {
         LoadContext* lc;
         png_uint_32 width, height;
+        png_textp png_text_ptr;
+        int num_text, i;
         int color_type;
+        gchar *key;
         gboolean have_alpha = FALSE;
         gboolean failed = FALSE;
         
@@ -538,7 +571,20 @@
                 }
                 return;
         }
+
+        /* Extract tEXt chunks and attach them as object data */
         
+        if (png_get_text (png_read_ptr, png_info_ptr, &png_text_ptr, &num_text)) {
+                for (i = 0; i < num_text; i++) {
+                        key = g_strconcat ("tEXt::", png_text_ptr[i].key, NULL);
+                        g_object_set_data_full (G_OBJECT (lc->pixbuf),
+                                                key,
+                                                g_strdup (png_text_ptr[i].text),
+                                                (GDestroyNotify) g_free);
+                        g_free (key);
+                }
+        }
+
         /* Notify the client that we are ready to go */
 
         if (lc->prepare_func)
@@ -653,6 +699,7 @@
 {
        png_structp png_ptr;
        png_infop info_ptr;
+       png_textp text_ptr = NULL;
        guchar *ptr;
        guchar *pixels;
        int x, y, j;
@@ -662,23 +709,30 @@
        int w, h, rowstride;
        int has_alpha;
        int bpc;
+       int num_keys;
 
+       num_keys = 0;
+
        if (keys && *keys) {
-               g_warning ("Bad option name '%s' passed to PNG saver",
-                          *keys);
-               return FALSE;
-#if 0
-               gchar **kiter = keys;
-               gchar **viter = values;
-
-               
-               while (*kiter) {
-                       
-                       ++kiter;
-                       ++viter;
+               gchar **kiter;
+               int     len;
+
+               for (kiter = keys; *kiter; kiter++) {
+                       len = strlen (*kiter);
+                       if (len < 6 || strncmp (*kiter, "tEXt::", 6)) {
+                                g_warning ("Bad option name '%s' passed to PNG saver",
+                                          *kiter);
+                               return FALSE;
+                       }
+                       len -= 6;
+                       if (len < 1 || len > 79) {
+                               g_warning ("tEXt keys passed as option to PNG saver must be of length 1-79");
+                               return FALSE;
+                       }
+                       num_keys++;
                }
-#endif
        }
+
        data = NULL;
        
        bpc = gdk_pixbuf_get_bits_per_sample (pixbuf);
@@ -704,7 +758,21 @@
                png_destroy_write_struct (&png_ptr, (png_infopp) NULL);
                return FALSE;
        }
+
+       if (num_keys > 0) {
+               text_ptr = g_new0 (png_text, num_keys);
+               for (j = 0; j < num_keys; j++) {
+                       text_ptr[j].compression = PNG_TEXT_COMPRESSION_NONE;
+                       text_ptr[j].key         = keys[j]+6;
+                       text_ptr[j].text        = values[j];
+                       text_ptr[j].text_length = (values[j] ? 
+                                                  strlen (values[j]) : 0);
+               }                       
+               png_set_text (png_ptr, info_ptr, text_ptr, num_keys);
+       }
+
        png_init_io (png_ptr, f);
+
        if (has_alpha) {
                png_set_IHDR (png_ptr, info_ptr, w, h, bpc,
                              PNG_COLOR_TYPE_RGB_ALPHA, PNG_INTERLACE_NONE,
@@ -762,6 +830,9 @@
 
        png_write_end (png_ptr, info_ptr);
        png_destroy_write_struct (&png_ptr, (png_infopp) NULL);
+
+       if (num_keys > 0)
+               g_free (text_ptr);
 
        return TRUE;
 }
Index: demos/testpixbuf-save.c
===================================================================
RCS file: /cvs/gnome/gtk+/demos/testpixbuf-save.c,v
retrieving revision 1.7
diff -u -r1.7 testpixbuf-save.c
--- demos/testpixbuf-save.c	2001/09/07 21:49:33	1.7
+++ demos/testpixbuf-save.c	2001/09/20 10:17:59
@@ -35,7 +35,10 @@
                         return;
                 }
 
-                if (!gdk_pixbuf_save (pixbuf, "foo.png", "png", &err, NULL)) {
+                if (!gdk_pixbuf_save (pixbuf, "foo.png", "png", 
+                                      &err,
+                                      "tEXt::Software", "testpixbuf-save",
+                                      NULL)) {
                         fprintf (stderr, "%s", err->message);
                         g_error_free (err);
                 }
Index: demos/testpixbuf-scale.c
===================================================================
RCS file: /cvs/gnome/gtk+/demos/testpixbuf-scale.c,v
retrieving revision 1.11
diff -u -r1.11 testpixbuf-scale.c
--- demos/testpixbuf-scale.c	2001/08/23 15:26:44	1.11
+++ demos/testpixbuf-scale.c	2001/09/20 10:17:59
@@ -63,6 +63,7 @@
 	GtkWidget *hbox, *label, *hscale;
 	GtkAdjustment *adjustment;
 	GtkRequisition scratch_requisition;
+        const gchar *creator;
         GError *error;
         
 	pixbuf_init ();
@@ -82,6 +83,11 @@
                 g_error_free (error);
 		exit(1);
 	}
+
+        creator = (const gchar *) g_object_get_data (G_OBJECT (pixbuf), 
+                                                     "tEXt::Software");
+        if (creator)
+                g_print ("%s was created by '%s'\n", argv[1], creator);
 
 	window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
 	gtk_signal_connect (GTK_OBJECT (window), "destroy",








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