wrlib: Added support for webp image

This patch is adding support for google webp image format, if you
don't know it a quick recap is to say that according to their tests
they claim it is better than png and jpeg.

Follow the link below for some more details:
https://developers.google.com/speed/webp/

Signed-off-by: Carlos R. Mafra <crmafra@gmail.com>

wrlib/load_webp.c

@@ -0,0 +1,138 @@
+/* load_webp.c - load WEBP image from file
+ *
+ * Raster graphics library
+ *
+ * Copyright (c) 2014 Window Maker Team
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Library General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2 of the License, or (at your option) any later version.
+ *
+ *  This library is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  Library General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Library General Public
+ *  License along with this library; if not, write to the Free
+ *  Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
+ *  MA 02110-1301, USA.
+ */
+
+#include "config.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <webp/decode.h>
+
+#include "wraster.h"
+#include "imgformat.h"
+
+
+RImage *RLoadWEBP(const char *file_name)
+{
+	FILE *file;
+	RImage *image = NULL;
+	char buffer[20];
+	int raw_data_size;
+	int r;
+	uint8_t *raw_data;
+	WebPBitstreamFeatures features;
+	uint8_t *ret = NULL;
+
+	file = fopen(file_name, "rb");
+	if (!file) {
+		RErrorCode = RERR_OPEN;
+		return NULL;
+	}
+
+	if (!fread(buffer, sizeof(buffer), 1, file)) {
+		RErrorCode = RERR_BADIMAGEFILE;
+		fclose(file);
+		return NULL;
+	}
+
+	if (!(buffer[ 0] == 'R' && buffer[ 1] == 'I' && buffer[ 2] == 'F' && buffer[ 3] == 'F' &&
+	      buffer[ 8] == 'W' && buffer[ 9] == 'E' && buffer[10] == 'B' && buffer[11] == 'P' &&
+	      buffer[12] == 'V' && buffer[13] == 'P' && buffer[14] == '8' &&
+#if WEBP_DECODER_ABI_VERSION < 0x0003	/* old versions don't support WEBPVP8X and WEBPVP8L */
+	      buffer[15] == ' ')) {
+#else
+	      (buffer[15] == ' ' || buffer[15] == 'X' || buffer[15] == 'L'))) {
+#endif
+		RErrorCode = RERR_BADFORMAT;
+		fclose(file);
+		return NULL;
+	}
+
+	fseek(file, 0L, SEEK_END);
+	raw_data_size = ftell(file);
+
+	if (raw_data_size <= 0) {
+		fprintf(stderr, "wrlib: Failed to find the WEBP file size for \"%s\"\n", file_name);
+		RErrorCode = RERR_BADIMAGEFILE;
+		fclose(file);
+		return NULL;
+	}
+
+	raw_data = (uint8_t *) malloc(raw_data_size);
+
+	if (!raw_data) {
+		RErrorCode = RERR_NOMEMORY;
+		fclose(file);
+		return NULL;
+	}
+
+	fseek(file, 0L, SEEK_SET);
+	r = fread(raw_data, 1, raw_data_size, file);
+	fclose(file);
+
+	if (r != raw_data_size) {
+		RErrorCode = RERR_READ;
+		free(raw_data);
+		return NULL;
+	}
+
+	if (WebPGetFeatures(raw_data, raw_data_size, &features) != VP8_STATUS_OK) {
+		fprintf(stderr, "wrlib: WebPGetFeatures has failed on \"%s\"\n", file_name);
+		RErrorCode = RERR_BADIMAGEFILE;
+		free(raw_data);
+		return NULL;
+	}
+
+	if (features.has_alpha) {
+		image = RCreateImage(features.width, features.height, True);
+		if (!image) {
+			RErrorCode = RERR_NOMEMORY;
+			free(raw_data);
+			return NULL;
+		}
+		ret = WebPDecodeRGBAInto(raw_data, raw_data_size, image->data,
+		                         features.width * features.height * 4,
+		                         features.width * 4);
+	} else {
+		image = RCreateImage(features.width, features.height, False);
+		if (!image) {
+			RErrorCode = RERR_NOMEMORY;
+			free(raw_data);
+			return NULL;
+		}
+		ret = WebPDecodeRGBInto(raw_data, raw_data_size, image->data,
+		                        features.width * features.height * 3,
+		                        features.width * 3);
+	}
+
+	free(raw_data);
+
+	if (!ret) {
+		fprintf(stderr, "wrlib: Failed to decode WEBP from file \"%s\"\n", file_name);
+		RErrorCode = RERR_BADIMAGEFILE;
+		RReleaseImage(image);
+		return NULL;
+	}
+
+	return image;
+}