imageviewer: gif viewer based on giflib-5.0.2

This adds ability to view gif images in rockbox.
Works both on color and gray/monochrome targets (greylib).
Aspect correction is supported as well.

Limitations:
- animated gifs are restricted to 32 frames
- animated gifs loop always (loopcount is ignored)
- plain text extension is not supported
- animated gifs with interframe delay = 0 are treated as still
  images (web browsers usually treat delay 0 as 100ms to prevent
  exhaustive CPU load by such images)

Change-Id: I61501f801ddcd403410e38d83e6bddc9883e7ede

1 files changed, 37 insertions, 0 deletions

diff --git a/apps/plugins/imageviewer/gif/gif_decoder.h b/apps/plugins/imageviewer/gif/gif_decoder.h
new file mode 100644
index 0000000000..444f54acf9
--- /dev/null
+++ b/apps/plugins/imageviewer/gif/gif_decoder.h
@@ -0,0 +1,37 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ *
+ * Copyright (c) 2012 Marcin Bukat
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+#define GIF_MAX_FRAMES 32
+
+struct gif_decoder {
+    unsigned char *mem;
+    size_t mem_size;
+    int width;
+    int height;
+    int frames_count;
+    int delay;
+    size_t native_img_size;
+    int error;
+};
+
+void gif_decoder_init(struct gif_decoder *decoder, void *mem, size_t size);
+void gif_open(char *filename, struct gif_decoder *d);
+void gif_decode(struct gif_decoder *d, void (*pf_progress)(int current, int total));
+