ubb-vga2: replaced threshold-based color mapping with color cube model

- ubb-vga.h (ccube_init, ccube_map), ccube.c: color mapper based on
  proximity in color cube
- grabfb.c (pattern, grabfb), ppmimg.c (pattern, convert): use the color
  cube mapper instead of inferios threshold-based mapping
- ubb-vga2.c (session): initialize the color cube
- ubb-vga.h (thres), grabfb.c (thres), ubb-vga2.c (usage, main): removed
  the threshold along with the option (-l) to set it
- Makefile (OBJS): added ccube.o

ubb-vga/Makefile

@@ -3,7 +3,7 @@ CC=mipsel-linux-gcc
 
 CFLAGS=-Wall -g -O9 -march=mips32
 LDFLAGS=-lm
-OBJS=ubb-vga2.o grabfb.o tstimg.o ppm.o ppmimg.o
+OBJS=ubb-vga2.o grabfb.o tstimg.o ppm.o ppmimg.o ccube.o
 
 .PHONY:		all asm sch clean spotless
 

ubb-vga/ccube.c

@@ -0,0 +1,58 @@
+/*
+ * ccube.c - Color mapper based on color cube model
+ *
+ * Written 2011 by Werner Almesberger
+ * Copyright 2011 Werner Almesberger
+ *
+ * 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 2 of the License, or
+ * (at your option) any later version.
+ */
+
+
+#include <stdint.h>
+
+#include "ubb-vga.h"
+
+
+#define	W_RGB	(256*0.5)
+#define	W_Y	(256*0.25)
+#define	W_0	(256*0.125)
+
+
+static struct col {
+	uint8_t r, g, b;
+} col[16];
+
+
+uint8_t ccube_map(uint8_t r, uint8_t g, uint8_t b)
+{
+	unsigned best = 0;
+	int best_i = 0;
+	unsigned d;
+	int i;
+
+	for (i = 0; i != 16; i++) {
+		d = (r-col[i].r)*(r-col[i].r)+
+		    (g-col[i].g)*(g-col[i].g)+
+		    (b-col[i].b)*(b-col[i].b);
+		if (!i || d < best) {
+			best = d;
+			best_i = i;
+		}
+	}
+	return best_i;
+}
+
+
+void ccube_init(void)
+{
+	int i;
+
+	for (i = 0; i != 16; i++) {
+		col[i].r = W_0+(i & R_VAL ? W_RGB : 0)+(i & Y_VAL ? W_Y : 0);
+		col[i].g = W_0+(i & G_VAL ? W_RGB : 0)+(i & Y_VAL ? W_Y : 0);
+		col[i].b = W_0+(i & B_VAL ? W_RGB : 0)+(i & Y_VAL ? W_Y : 0);
+	}
+}

ubb-vga/grabfb.c

@@ -17,15 +17,6 @@
 #include "ubb-vga.h"
 
 
-uint8_t thres = 63;
-
-
-static uint8_t pattern(int r, int g, int b)
-{
-	return ((r ? R_VAL : 0) | (g ? G_VAL : 0) | (b ? B_VAL : 0))*0x11;
-}
-
-
 void grabfb(void *f, int xres, int yres)
 {
 	uint32_t *fb = map(0x01d00000, 4*320*240);
@@ -42,8 +33,7 @@ void grabfb(void *f, int xres, int yres)
 			r = pix >> 16;
 			g = pix >> 8;
 			b = pix;
-			p[0] = p[320] =
-			    pattern(r >= thres, g >= thres, b >= thres);
+			p[0] = p[320] = ccube_map(r, g, b)*0x11;
 			p++;
 		}
 		p += 320;

ubb-vga/ppmimg.c

@@ -22,12 +22,6 @@
 char *img_name;
 
 
-static uint8_t pattern(int r, int g, int b)
-{
-	return (r ? R_VAL : 0) | (g ? G_VAL : 0) | (b ? B_VAL : 0);
-}
-
-
 static void convert(uint8_t *f, int xres, int yres, uint8_t *ppm)
 {
 	int x, y;
@@ -35,8 +29,7 @@ static void convert(uint8_t *f, int xres, int yres, uint8_t *ppm)
 
 	for (y = 0; y != yres; y++)
 		for (x = 0; x != xres; x++) {
-			v = pattern(ppm[0] >= thres, ppm[1] >= thres,
-			    ppm[2] >= thres);
+			v = ccube_map(ppm[0], ppm[1], ppm[2]);
 			if (x & 1) {
 				*f++ = last | v;
 			} else {

ubb-vga/ubb-vga.h

@@ -26,9 +26,12 @@
 void *map(off_t addr, size_t size);
 
 
-/* grabfb.c */
+/* ccube.c */
 
-extern uint8_t thres;
+uint8_t ccube_map(uint8_t r, uint8_t g, uint8_t b);
+void ccube_init(void);
+
+/* grabfb.c */
 
 void grabfb(void *f, int xres, int yres);
 

ubb-vga/ubb-vga2.c

@@ -396,6 +396,7 @@ static void session(void (*gen)(void *fb, int xres, int yres), int frames)
 	int i;
 
 	memset(f, 0, sizeof(f));
+	ccube_init();
 	gen(f, 640, 480);
 
 	disable_interrupts();
@@ -410,10 +411,9 @@ static void session(void (*gen)(void *fb, int xres, int yres), int frames)
 static void usage(const char *name)
 {
 	fprintf(stderr,
-"usage: %s [-l threshold] [-t] frames [file]\n\n"
+"usage: %s [-t] frames [file]\n\n"
 "  frames  number of frames to display\n"
 "  file    PPM file\n\n"
-"  -l threshold  channel on/off threshold\n"
 "  -t            generate a test image\n"
     , name);
 	exit(1);
@@ -426,11 +426,8 @@ int main(int argc, char *const *argv)
 	int frames;
 	int c;
 
-	while ((c = getopt(argc, argv, "l:t")) != EOF)
+	while ((c = getopt(argc, argv, "t")) != EOF)
 		switch (c) {
-		case 'l':
-			thres = atoi(optarg);
-			break;
 		case 't':
 			gen = tstimg;
 			break;