Diff: pnm-utils.c

Revision:

0:fa7450a43b99

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pnm-utils.c	Mon Dec 04 09:32:20 2017 +0000
@@ -0,0 +1,162 @@
+/*
+  Plastic Logic EPD project on MSP430
+
+  Copyright (C) 2013, 2014 Plastic Logic Limited
+
+  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 3 of the License, or
+  (at your option) any later version.
+
+  This program 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 General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/*
+ * pnm-utils.c -- Utilities for dealing with PNM format graphics files
+ *
+ * Authors:
+ *   Nick Terry <nick.terry@plasticlogic.com>
+ *   Guillaume Tucker <guillaume.tucker@plasticlogic.com>
+ *
+ * Utilities for dealing with PNM format graphics files
+ * We are only interested in PGM and PBM
+ *
+ * Details of the format can be found at:
+ * http://en.wikipedia.org/wiki/Netpbm_format
+ * However, this seems to indicate that the header format is more free format
+ * http://paulbourke.net/dataformats/ppm/
+ * Lines terminated with cr and/or lf or just white space
+ * Header example 1
+ * P6 1024 788 255
+ * Header example 2
+ * P6
+ * 1024 788
+ * # A comment
+ * 255
+ * Header example 3
+ * P3
+ * 1024 # the image width
+ * 788 # the image height
+ * # A comment
+ * 1023
+ *
+ *
+ * P4
+ * # Comment string
+ * 24 7
+ *
+ * P5
+ * # Comment string
+ * 24 7
+ * 15
+ *
+ */
+
+#include <stdlib.h>
+#include "assert.h"
+#include "ChaN/ff.h"
+#include "pnm-utils.h"
+
+int pnm_read_int32(FIL *pnm_file, int32_t *value)
+{
+	UINT count;
+	char ch;
+	int digits = 0;
+	int in_comment = 0;
+	int found = 0;
+	int32_t val = 0;
+
+	assert(pnm_file != NULL);
+	assert(value != NULL);
+
+	while (!found &&
+			(f_read(pnm_file,&ch,1,&count) == FR_OK) && count == 1)
+	{
+		switch (ch)
+		{
+			case '#':
+				in_comment = 1;
+				break;
+			case ' ':
+			case '\t':
+			case '\r':
+			case '\n':
+				if (!in_comment)
+				{
+					if (digits) {
+						found = 1;
+					}
+				}
+				if (ch == '\r' || ch == '\n')
+					in_comment = 0;
+				break;
+			case '0': case '1': case '2': case '3': case '4':
+			case '5': case '6': case '7': case '8': case '9':
+				if (!in_comment) {
+					val = val * 10 + (ch - '0');
+					digits++;
+
+					if (f_eof(pnm_file)) {
+						found = 1;
+					}
+				}
+				break;
+			default:
+				break;
+		}
+	}
+
+	if (!found)
+		return -1;
+
+	*value = val;
+
+	return 0;
+}
+
+int pnm_read_header(FIL *pnm_file, struct pnm_header *hdr)
+{
+	char buffer[2];
+	UINT count;
+
+	assert(pnm_file);
+	assert(hdr);
+
+	hdr->type = PNM_UNKNOWN;
+
+	if (f_read(pnm_file,buffer,2,&count) != FR_OK)
+		goto read_error;
+
+	if (buffer[0] != 'P')
+		goto format_error;
+
+	if (buffer[1] == '4')
+		hdr->type = PNM_BITMAP;
+	else if (buffer[1] == '5')
+		hdr->type = PNM_GREYSCALE;
+	else
+		goto format_error;
+
+	hdr->max_gray = 1;
+	hdr->width = pnm_read_int(pnm_file);
+	hdr->height = pnm_read_int(pnm_file);
+
+	if (hdr->type == PNM_GREYSCALE) {
+		hdr->max_gray = pnm_read_int(pnm_file);
+	}
+	// check to see if any of the data items were not read correctly
+	if (hdr->width <= 0 || hdr->height <= 0 || hdr->max_gray <= 0)
+		goto format_error;
+
+	// read pointer is now positioned at start of image data
+	return 0;
+
+format_error:
+read_error:
+	return -1;
+}