[gthumb: 83/129] add support for png dimensions

[Paolo Bacchilega <paobac src gnome org>]

commit f1bcba8883688841cd29937eb0371650f82c3d23
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Mon Apr 25 17:32:39 2011 +0200

    add support for png dimensions

 .../image_viewer/gth-metadata-provider-image.c     |   39 ++++++++++++++++++--
 1 files changed, 35 insertions(+), 4 deletions(-)
---
diff --git a/extensions/image_viewer/gth-metadata-provider-image.c b/extensions/image_viewer/gth-metadata-provider-image.c
index 58901ab..3d43635 100644
--- a/extensions/image_viewer/gth-metadata-provider-image.c
+++ b/extensions/image_viewer/gth-metadata-provider-image.c
@@ -84,12 +84,43 @@ gth_metadata_provider_image_read (GthMetadataProvider *self,
 					    NULL,
 					    NULL);
 		if (size >= 0) {
+			if ((size >= 24)
+
+			    /* PNG signature */
+
+			    && (buffer[0] == 0x89)
+			    && (buffer[1] == 0x50)
+			    && (buffer[2] == 0x4E)
+			    && (buffer[3] == 0x47)
+			    && (buffer[4] == 0x0D)
+			    && (buffer[5] == 0x0A)
+			    && (buffer[6] == 0x1A)
+			    && (buffer[7] == 0x0A)
+
+			    /* IHDR Image header */
+
+			    && (buffer[12] == 0x49)
+    			    && (buffer[13] == 0x48)
+    			    && (buffer[14] == 0x44)
+    			    && (buffer[15] == 0x52))
+			{
+				/* PNG */
+
+				width  = (buffer[16] << 24) + (buffer[17] << 16) + (buffer[18] << 8) + buffer[19];
+				height = (buffer[20] << 24) + (buffer[21] << 16) + (buffer[22] << 8) + buffer[23];
+
+				format_recognized = TRUE;
+				description = "PNG";
+			}
+
 #if HAVE_LIBJPEG
-			if ((size >= 4)
-			    && (buffer[0] == 0xff)
-			    && (buffer[1] == 0xd8)
-			    && (buffer[2] == 0xff))
+			else if ((size >= 4)
+				 && (buffer[0] == 0xff)
+				 && (buffer[1] == 0xd8)
+				 && (buffer[2] == 0xff))
 			{
+				/* JPEG */
+
 				GthTransform orientation;
 
 				if (g_seekable_can_seek (G_SEEKABLE (stream))) {