#
# rgb2gif transparency patch for libungif-4.1.0 by candy
#
# NO WARRANTY
#
# Install:
#  cd /usr/ports/graphics/libungif
#  make patch
#  cd work/libungif-4.1.0
#  patch -p < this_patch
#  cd ../..
#  make all && make install

--- lib/egif_lib.c.orig	Fri Feb 18 17:09:02 2000
+++ lib/egif_lib.c	Fri Feb 18 17:09:40 2000
@@ -819,3 +819,20 @@
 
     return(GIF_OK);
 }
+
+int
+EGifPutGraphicControlExtension(GifFileType *GifFile, int DisposalMethod, int UserInputFlag, int TransparentColorFlag, int DelayTime, int TransparentColorIndex)
+{
+	GifByteType buf[4];
+	buf[0] = 0x21; /* Extension Introducer */
+	buf[1] = 0xf9; /* Graphic ControlLabel */
+	buf[2] = 4; /* Block Size */
+	buf[3] = ((DisposalMethod & 7) << 2) | (!!UserInputFlag << 1) | !!TransparentColorFlag;
+	WRITE(GifFile, buf, 4);
+	EGifPutWord((DelayTime & 0xffff), GifFile);
+	buf[0] = TransparentColorIndex;
+	buf[1] = 0x00; /* Block Terminator */
+	WRITE(GifFile, buf, 2);
+	return GIF_OK;
+}
+
--- util/rgb2gif.c.orig	Mon Sep  7 04:15:33 1998
+++ util/rgb2gif.c	Fri Feb 18 17:27:43 2000
@@ -32,6 +32,7 @@
 #include <string.h>
 #include <fcntl.h>
 #include "gif_lib.h"
+extern int EGifPutGraphicControlExtension(GifFileType *GifFile, int DisposalMethod, int UserInputFlag, int TransparentColorFlag, int DelayTime, int TransparentColorIndex);
 #include "getarg.h"
 
 #define PROGRAM_NAME	"RGB2Gif"
@@ -58,7 +59,7 @@
 static char
     *CtrlStr =
 	PROGRAM_NAME
-	" q%- c%-#Colors!d 1%- s!-Width|Height!d!d h%- RGBFile!*s";
+	" q%- c%-#Colors!d 1%- s!-Width|Height!d!d h%- t%-TransparentColor!s RGBFile!*s";
 #endif /* SYSV */
 
 /* Make some variables global, so we could access them faster: */
@@ -68,6 +69,7 @@
     OneFileFlag = FALSE,
     HelpFlag = FALSE,
     ColorMapSize = 256;
+static long TransparentColor = -1;
 
 static void LoadRGB(char *FileName,
 		    int OneFileFlag,
@@ -80,6 +82,35 @@
 		    int ExpColorMapSize, int Width, int Height);
 static void QuitGifError(GifFileType *GifFile);
 
+static long
+parse_color_name(const char *name)
+{
+	long rgb = -1;
+	int err = -1;
+	if (name[0] == '#') {
+		if (strlen(name + 1) == 6) {
+			const unsigned char *p = (const unsigned char *)name + 1;
+			int i;
+			unsigned char ppp[3];
+			err = 0;
+			for (i = 0; i < 3; i++) {
+				if (isxdigit(p[i * 2]) && isxdigit(p[i * 2 + 1])) {
+					char buf[3];
+					buf[0] = p[i * 2];
+					buf[1] = p[i * 2 + 1];
+					buf[3] = '\0';
+					ppp[i] = strtoul(buf, 0, 16);
+				}
+				else
+					err = -1;
+			}
+			if (err == 0)
+				rgb =  ((unsigned long)ppp[0] << 16) | ((unsigned long)ppp[1] << 8) | ppp[2];
+		}
+	}
+	return rgb;
+}
+
 /******************************************************************************
 * Interpret the command line and scan the given GIF file.		      *
 ******************************************************************************/
@@ -90,10 +121,13 @@
     GifByteType *RedBuffer = NULL, *GreenBuffer = NULL, *BlueBuffer = NULL,
 	*OutputBuffer = NULL;
     ColorMapObject *OutputColorMap = NULL;
+    int TransparentFlag = 0;
+    char *TransparentColorName = NULL;
 
     if ((Error = GAGetArgs(argc, argv, CtrlStr, &GifQuietPrint,
 		&ColorFlag, &ExpNumOfColors, &OneFileFlag,
 		&SizeFlag, &Width, &Height, &HelpFlag,
+		&TransparentFlag, &TransparentColorName,
 		&NumFiles, &FileName)) != FALSE ||
 		(NumFiles > 1 && !HelpFlag)) {
 	if (Error)
@@ -109,6 +143,13 @@
 	GAPrintHowTo(CtrlStr);
 	exit(0);
     }
+    if (TransparentFlag) {
+    	TransparentColor = parse_color_name(TransparentColorName);
+    	if (TransparentColor < 0) {
+		fprintf(stderr, "color name should be '#RRGGBB'\n");
+		exit(1);
+	}
+    }
 
     ColorMapSize = 1 << ExpNumOfColors;
 
@@ -135,6 +176,7 @@
     free((char *) BlueBuffer);
 
     SaveGif(OutputBuffer, OutputColorMap, ExpNumOfColors, Width, Height);
+    exit(0);
 }
 
 /******************************************************************************
@@ -244,6 +286,32 @@
     }
 }
 
+static int
+lookup_color(const ColorMapObject *ColorMap, long rgb)
+{
+	int i = 0, found = -1;
+	while (i < ColorMap->ColorCount && found < 0) {
+		long col =  ((unsigned long)ColorMap->Colors[i].Red << 16) | ((unsigned long)ColorMap->Colors[i].Green << 8) | ColorMap->Colors[i].Blue;
+		if (col == rgb)
+			found = i;
+		i++;
+	}
+	return found;
+}
+
+static int
+EGifPutGraphExt(GifFileType *GifFile, const ColorMapObject *ColorMap)
+{
+	int err = GIF_OK;
+	if (TransparentColor >= 0 && ColorMap != NULL) {
+		int idx = lookup_color(ColorMap, TransparentColor);
+		if (idx >= 0) {
+			err = EGifPutGraphicControlExtension(GifFile, 0, 0, 1, 0, idx);
+		}
+	}
+	return err;
+}
+
 /******************************************************************************
 * Save the GIF resulting image.						      *
 ******************************************************************************/
@@ -262,6 +330,7 @@
     if (EGifPutScreenDesc(GifFile,
 			  Width, Height, ExpColorMapSize, 0,
 			  OutputColorMap) == GIF_ERROR ||
+	EGifPutGraphExt(GifFile, OutputColorMap) == GIF_ERROR ||
 	EGifPutImageDesc(GifFile,
 			 0, 0, Width, Height, FALSE, NULL) ==
 	                                                             GIF_ERROR)