WRaster: add functions to save image on disk

This patch adds the RSaveTitledImage() function to the WRaster lib
to be able to save file on disk either as a PNG or a JPEG file.
Those two formats depends on optional external libs.
The function can take an optional title/comment which will
be save inside the file.

The WRaster lib and header versions are bumped.

wrlib/save_jpeg.c

@@ -0,0 +1,104 @@
+/* save_jpeg.c - save JPEG image
+ *
+ * Raster graphics library
+ *
+ * Copyright (c) 2023 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 <assert.h>
+#include <errno.h>
+#include <jpeglib.h>
+
+#include "wraster.h"
+#include "imgformat.h"
+#include "wr_i18n.h"
+
+/*
+ *  Save RImage to JPEG image
+ */
+
+Bool RSaveJPEG(RImage *img, const char *filename, char *title)
+{
+	FILE *file;
+	int x, y, img_depth;
+	char *buffer;
+	RColor pixel;
+	struct jpeg_compress_struct cinfo;
+	struct jpeg_error_mgr jerr;
+	JSAMPROW row_pointer;
+
+	file = fopen(filename, "wb");
+	if (!file) {
+		RErrorCode = RERR_OPEN;
+		return False;
+	}
+
+	if (img->format == RRGBAFormat)
+		img_depth = 4;
+	else
+		img_depth = 3;
+
+	/* collect separate RGB values to a buffer */
+	buffer = malloc(sizeof(char) * 3 * img->width * img->height);
+	for (y = 0; y < img->height; y++) {
+		for (x = 0; x < img->width; x++) {
+			RGetPixel(img, x, y, &pixel);
+			buffer[y*img->width*3+x*3+0] = (char)(pixel.red);
+			buffer[y*img->width*3+x*3+1] = (char)(pixel.green);
+			buffer[y*img->width*3+x*3+2] = (char)(pixel.blue);
+		}
+	}
+
+	/* Setup Exception handling */
+	cinfo.err = jpeg_std_error(&jerr);
+
+	/* Initialize cinfo structure */
+	jpeg_create_compress(&cinfo);
+	jpeg_stdio_dest(&cinfo, file);
+
+	cinfo.image_width = img->width;
+	cinfo.image_height = img->height;
+	cinfo.input_components = 3;
+	cinfo.in_color_space = JCS_RGB;
+
+	jpeg_set_defaults(&cinfo);
+	jpeg_set_quality(&cinfo, 85, TRUE);
+	jpeg_start_compress(&cinfo, TRUE);
+
+	/* Set title if any */
+	if (title)
+		jpeg_write_marker(&cinfo, JPEG_COM, (const JOCTET*)title, strlen(title));
+
+	while (cinfo.next_scanline < cinfo.image_height) {
+        	row_pointer = (JSAMPROW) &buffer[cinfo.next_scanline * img_depth * img->width];
+		jpeg_write_scanlines(&cinfo, &row_pointer, 1);
+	}
+
+	jpeg_finish_compress(&cinfo);
+	
+	/* Clean */
+	free(buffer);
+	fclose(file);
+
+	return True;
+}