add gif2if

3 files changed, 192 insertions, 3 deletions

diff --git a/Makefile b/Makefile
index 5187f6b..fe842a9 100644
--- a/Makefile
+++ b/Makefile
@@ -3,10 +3,10 @@
 
 include config.mk
 
-SRC = png2if.c if2png.c jpg2if.c
+SRC = png2if.c if2png.c jpg2if.c gif2if.c
 OBJ = ${SRC:.c=.o}
 
-all: options png2if if2png jpg2if
+all: options png2if if2png jpg2if gif2if
 
 options:
 	@echo imagefile build options:
@@ -20,6 +20,10 @@ options:
 
 ${OBJ}: config.mk
 
+gif2if: gif2if.o
+	@echo CC -o $@
+	@${CC} -o $@ gif2if.o ${LDFLAGS} ${GIF_LIBS}
+
 jpg2if: jpg2if.o
 	@echo CC -o $@
 	@${CC} -o $@ jpg2if.o ${LDFLAGS} ${JPEG_LIBS}
@@ -34,7 +38,7 @@ if2png: if2png.o
 
 clean:
 	@echo cleaning
-	@rm -f png2if if2png jpg2if ${OBJ}
+	@rm -f png2if if2png jpg2if gif2if ${OBJ}
 
 install: all
 	@echo installing executable files to ${DESTDIR}${PREFIX}/bin
diff --git a/config.mk b/config.mk
index 2763f09..06616af 100644
--- a/config.mk
+++ b/config.mk
@@ -7,6 +7,7 @@ PREFIX = /usr/local
 LIBS =
 PNG_LIBS = -lpng
 JPEG_LIBS = -ljpeg
+GIF_LIBS = -lgif
 
 # flags
 CFLAGS = -std=c90 -ansi -pedantic -Wall -Wextra -Os
diff --git a/gif2if.c b/gif2if.c
new file mode 100644
index 0000000..e027954
--- /dev/null
+++ b/gif2if.c
@@ -0,0 +1,184 @@
+/* See LICENSE file for copyright and license details.
+ * code borrowed from util/gif2rgb.c from giflib-5.0 */
+#include <arpa/inet.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <gif_lib.h>
+#include "arg.h"
+
+char *argv0;
+
+static void
+usage(void)
+{
+	fprintf(stderr, "usage: %s\n", argv0);
+	exit(EXIT_FAILURE);
+}
+
+static void
+die(const char *s) {
+	fputs(s, stderr);
+	exit(EXIT_FAILURE);
+}
+
+void
+gif_print_error(int code)
+{
+	const char *err = GifErrorString(code);
+
+	if(err != NULL)
+		fprintf(stderr, "GIF-LIB error: %s.\n", err);
+	else
+		fprintf(stderr, "GIF-LIB undefined error %d.\n", code);
+	exit(EXIT_FAILURE);
+}
+
+void *
+emalloc(size_t size) {
+	void *p;
+
+	if(!(p = malloc(size)))
+		die("can't malloc\n");
+	return p;
+}
+
+int
+main(int argc, char *argv[])
+{
+	GifRecordType recordtype;
+	GifFileType *giffile;
+	GifRowType * gifrows;
+	GifByteType *extension;
+	GifColorType *colormapentry;
+	ColorMapObject *colormap;
+	uint32_t width, height, rwidth, rheight, val_be;
+	uint32_t i, j, k;
+	size_t gif_row_len;
+	uint8_t *if_row;
+	int errorcode, extcode, row, col, imagenum = 0;
+	int interlacedoffset[] = { 0, 4, 2, 1 };
+	int interlacedjumps[] = { 8, 8, 4, 2 };
+
+	ARGBEGIN {
+	default:
+		usage();
+	} ARGEND;
+
+	if (argc != 0)
+		usage();
+
+	/* load gif */
+	if ((giffile = DGifOpenFileHandle(0, &errorcode)) == NULL)
+		gif_print_error(errorcode);
+
+	width = (uint32_t)giffile->SWidth;
+	height = (uint32_t)giffile->SHeight;
+	gif_row_len = giffile->SWidth * sizeof(GifPixelType);
+	gifrows = emalloc(giffile->SHeight * sizeof(GifRowType));
+	gifrows[0] = emalloc(gif_row_len);
+
+	/* set color to BackGround. */
+	for (i = 0; i < width; i++)
+		gifrows[0][i] = giffile->SBackGroundColor;
+	for(i = 1; i < height; i++) {
+		gifrows[i] = emalloc(gif_row_len);
+		memcpy(gifrows[i], gifrows[0], gif_row_len);
+	}
+
+	/* scan the content of the GIF file and load the image(s) in: */
+	do {
+		if (DGifGetRecordType(giffile, &recordtype) == GIF_ERROR)
+			gif_print_error(giffile->Error);
+
+		switch (recordtype) {
+		case IMAGE_DESC_RECORD_TYPE:
+			if (DGifGetImageDesc(giffile) == GIF_ERROR)
+				gif_print_error(giffile->Error);
+
+			/* image position relative to Screen. */
+			row = giffile->Image.Top;
+			col = giffile->Image.Left;
+			rwidth = giffile->Image.Width;
+			rheight = giffile->Image.Height;
+			if (giffile->Image.Left + giffile->Image.Width > giffile->SWidth ||
+				giffile->Image.Top + giffile->Image.Height > giffile->SHeight) {
+				fprintf(stderr, "Image %d is not confined to screen dimension, aborted.\n", imagenum);
+				exit(EXIT_FAILURE);
+			}
+			if (giffile->Image.Interlace) {
+				/* need to perform 4 passes on the images: */
+				for (i = 0; i < 4; i++) {
+					for (j = row + interlacedoffset[i]; j < row + rheight; j += interlacedjumps[i]) {
+						if (DGifGetLine(giffile, &gifrows[j][col], rwidth) == GIF_ERROR)
+							gif_print_error(giffile->Error);
+					}
+				}
+			} else {
+				for (i = 0; i < rheight; i++) {
+					if (DGifGetLine(giffile, &gifrows[row++][col], rwidth) == GIF_ERROR)
+						gif_print_error(giffile->Error);
+				}
+			}
+			/* this is set to disallow multiple images */
+			recordtype = TERMINATE_RECORD_TYPE;
+			imagenum++;
+			break;
+		case EXTENSION_RECORD_TYPE:
+			/* Skip any extension blocks in file: */
+			if (DGifGetExtension(giffile, &extcode, &extension) == GIF_ERROR)
+				gif_print_error(giffile->Error);
+			while (extension != NULL) {
+				if (DGifGetExtensionNext(giffile, &extension) == GIF_ERROR)
+					gif_print_error(giffile->Error);
+			}
+			break;
+		case TERMINATE_RECORD_TYPE:
+			 break;
+		default:
+			break;
+		}
+	} while (recordtype != TERMINATE_RECORD_TYPE);
+
+	if(giffile->Image.ColorMap)
+		colormap = giffile->Image.ColorMap;
+	else
+		colormap = giffile->SColorMap;
+
+	if(colormap == NULL)
+		die("Gif Image does not have a colormap\n");
+
+	 /* write header with big endian width and height-values */
+	fprintf(stdout, "imagefile");
+	val_be = htonl(width);
+	fwrite(&val_be, sizeof(uint32_t), 1, stdout);
+	val_be = htonl(height);
+	fwrite(&val_be, sizeof(uint32_t), 1, stdout);
+
+	gif_row_len = width * strlen("RGBA");
+	if_row = emalloc(gif_row_len);
+
+	/* write data */
+	for (i = 0; i < height; i++) {
+		for(j = 0, k = 0; j < width; j++, k += 4) {
+			colormapentry = &colormap->Colors[gifrows[i][j]];
+			if_row[k] = colormapentry->Red;
+			if_row[k+1] = colormapentry->Green;
+			if_row[k+2] = colormapentry->Blue;
+			if_row[k+3] = 255; /* TODO: mask? */
+		}
+		if (fwrite(if_row, 1, gif_row_len, stdout) != gif_row_len)
+			die("fwrite() failed\n");
+	}
+
+	/* cleanup */
+	for(i = 0; i < height; i++)
+		free(gifrows[i]);
+	free(gifrows);
+	free(if_row);
+
+	return EXIT_SUCCESS;
+}