From 70ab2f42231480d550afdc9e493c342688e32f70 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Tue, 29 Jun 2021 00:58:09 -0400
Subject: [PATCH] hgr-util: png2hgr: try to autodetect correct black and white
 better

this is a bit tricky, because we support forcing black/white colors by
using slightly different palette entries, so we don't want to completely
ignore the difference in case the image is trying to force one or another
of the black/white colors for alignment or xdraw reasons
---
 utils/hgr-utils/png2hgr.c | 77 +++++++++++++++++++--------------------
 1 file changed, 38 insertions(+), 39 deletions(-)

diff --git a/utils/hgr-utils/png2hgr.c b/utils/hgr-utils/png2hgr.c
index b978ec74..22ad1f9b 100644
--- a/utils/hgr-utils/png2hgr.c
+++ b/utils/hgr-utils/png2hgr.c
@@ -279,65 +279,64 @@ static int color_low(int color) {
 	return 0;
 }
 
+/* also count any black/white */
+static int color_high_bw(int color) {
+	if (color>3) return 1;
+	if ((color==0) || (color==3)) return 1;
+	return 0;
+}
+
+static int color_low_bw(int color) {
+	if (color<4) return 1;
+	if ((color==4) || (color==7)) return 1;
+	return 0;
+}
 
 static int colors_to_bytes(unsigned char colors[14],
 			unsigned char *byte1,
 			unsigned char *byte2) {
 
+	int i;
 	int highbit1=0,highbit2=0,lowbit1=0,lowbit2=0;
+	int bwhigh1=0,bwlow1=0;
+	int bwhigh2=0,bwlow2=0;
 	int hb1,hb2;
 	int error=0;
 
 	*byte1=0;
 	*byte2=0;
 
-	highbit1+=color_high(colors[0]);
-	highbit1+=color_high(colors[1]);
-	highbit1+=color_high(colors[2]);
-	highbit1+=color_high(colors[3]);
-	highbit1+=color_high(colors[4]);
-	highbit1+=color_high(colors[5]);
-	highbit1+=color_high(colors[6]);
+	for(i=0;i<7;i++) {
+		highbit1+=color_high(colors[i]);
+		lowbit1+=color_low(colors[i]);
+		bwhigh1+=color_high_bw(colors[i]);
+		bwlow1+=color_low_bw(colors[i]);
+	}
 
-	highbit2+=color_high(colors[7]);
-	highbit2+=color_high(colors[8]);
-	highbit2+=color_high(colors[9]);
-	highbit2+=color_high(colors[10]);
-	highbit2+=color_high(colors[11]);
-	highbit2+=color_high(colors[12]);
-	highbit2+=color_high(colors[13]);
+	for(i=7;i<14;i++) {
+		highbit2+=color_high(colors[i]);
+		lowbit2+=color_low(colors[i]);
+		bwhigh2+=color_high_bw(colors[i]);
+		bwlow2+=color_low_bw(colors[i]);
+	}
 
-	lowbit1+=color_low(colors[0]);
-	lowbit1+=color_low(colors[1]);
-	lowbit1+=color_low(colors[2]);
-	lowbit1+=color_low(colors[3]);
-	lowbit1+=color_low(colors[4]);
-	lowbit1+=color_low(colors[5]);
-	lowbit1+=color_low(colors[6]);
-
-	lowbit2+=color_low(colors[7]);
-	lowbit2+=color_low(colors[8]);
-	lowbit2+=color_low(colors[9]);
-	lowbit2+=color_low(colors[10]);
-	lowbit2+=color_low(colors[11]);
-	lowbit2+=color_low(colors[12]);
-	lowbit2+=color_low(colors[13]);
-
-
-
-	if (highbit1==7) hb1=1;
-	else if (lowbit1==7) hb1=0;
+	if (highbit1==7) hb1=1;			// all were high bit set
+	else if (lowbit1==7) hb1=0;		// all were lo bit set
+	else if (bwhigh1==7) hb1=1;		// ignore black/white
+	else if (bwlow1==7) hb1=0;
 	else {
 		error=1;
-		if (highbit1>lowbit1) hb1=1;
+		if (bwhigh1>bwlow1) hb1=1;
 		else hb1=0;
 	}
 
-	if (highbit2==7) hb2=1;
-	else if (lowbit2==7) hb2=0;
+	if (highbit2==7) hb2=1;			// all were high bit set
+	else if (lowbit2==7) hb2=0;		// all were lo bit set
+	else if (bwhigh2==7) hb2=1;		// ignore black/white
+	else if (bwlow2==7) hb2=0;
 	else {
-		error=2;
-		if (highbit2>lowbit2) hb2=1;
+		error=1;
+		if (bwhigh2>bwlow2) hb2=1;
 		else hb2=0;
 	}