SCHEME(1) FreeBSD General Commands Manual SCHEME(1)

scheme
color scheme

scheme [-Xacghilmstx] [-p n]

scheme generates a color scheme and outputs it in a number of formats.

The arguments are as follows:

Output Xresources for xterm(1).
Generate the 16 ANSI colors. This is the default.
Output a C enum.
Output a swatch PNG.
Output floating point HSV.
Swap black and white.
Output Linux console OSC sequences.
Output a mintty(1) theme. Use with -t.
n
Generate only the color n.
Output CSS for classes named fgn and bgn.
Generate the 16 ANSI colors as well as background, foreground, bold, selection and cursor colors.
Output hexadecimal RGB. This is the default.
February 6, 2021 FreeBSD 12.2-RELEASE-p7

scheme.c in git

/* Copyright (C) 2018, 2019  C. McEnroe <june@causal.agency>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <err.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>

#include "png.h"

typedef unsigned uint;
typedef unsigned char byte;

struct HSV {
	double h, s, v;
};

struct RGB {
	byte r, g, b;
};

static struct RGB convert(struct HSV o) {
	double c = o.v * o.s;
	double h = o.h / 60.0;
	double x = c * (1.0 - fabs(fmod(h, 2.0) - 1.0));
	double m = o.v - c;
	double r = m, g = m, b = m;
	if      (h <= 1.0) { r += c; g += x; }
	else if (h <= 2.0) { r += x; g += c; }
	else if (h <= 3.0) { g += c; b += x; }
	else if (h <= 4.0) { g += x; b += c; }
	else if (h <= 5.0) { r += x; b += c; }
	else if (h <= 6.0) { r += c; b += x; }
	return (struct RGB) { r * 255.0, g * 255.0, b * 255.0 };
}

static const struct HSV
R = {   0.0, 1.0, 1.0 },
Y = {  60.0, 1.0, 1.0 },
G = { 120.0, 1.0, 1.0 },
C = { 180.0, 1.0, 1.0 },
B = { 240.0, 1.0, 1.0 },
M = { 300.0, 1.0, 1.0 };

static struct HSV x(struct HSV o, double hd, double sf, double vf) {
	return (struct HSV) {
		fmod(o.h + hd, 360.0),
		fmin(o.s * sf, 1.0),
		fmin(o.v * vf, 1.0),
	};
}

enum {
	Black, Red, Green, Yellow, Blue, Magenta, Cyan, White,
	Dark = 0,
	Light = 8,
	Background = 16,
	Foreground,
	Bold,
	Selection,
	Cursor,
	SchemeLen,
};
static struct HSV scheme[SchemeLen];
static struct HSV *dark = &scheme[Dark];
static struct HSV *light = &scheme[Light];

static void generate(void) {
	light[Black]   = x(R, +45.0, 0.3, 0.3);
	light[Red]     = x(R, +10.0, 0.9, 0.8);
	light[Green]   = x(G, -55.0, 0.8, 0.6);
	light[Yellow]  = x(Y, -20.0, 0.8, 0.8);
	light[Blue]    = x(B, -55.0, 0.4, 0.5);
	light[Magenta] = x(M, +45.0, 0.4, 0.6);
	light[Cyan]    = x(C, -60.0, 0.3, 0.6);
	light[White]   = x(R, +45.0, 0.3, 0.8);

	dark[Black] = x(light[Black], 0.0, 1.0, 0.3);
	dark[White] = x(light[White], 0.0, 1.0, 0.75);
	for (uint i = Red; i < White; ++i) {
		dark[i] = x(light[i], 0.0, 1.0, 0.8);
	}

	scheme[Background] = x(dark[Black],  0.0, 1.0, 0.9);
	scheme[Foreground] = x(light[White], 0.0, 1.0, 0.9);
	scheme[Bold]       = x(light[White], 0.0, 1.0, 1.0);
	scheme[Selection]  = x(light[Red], +10.0, 1.0, 0.8);
	scheme[Cursor]     = x(dark[White],  0.0, 1.0, 0.8);
}

static void swap(struct HSV *a, struct HSV *b) {
	struct HSV c = *a;
	*a = *b;
	*b = c;
}

static void invert(void) {
	swap(&dark[Black], &light[White]);
	swap(&dark[White], &light[Black]);
}

typedef void OutputFn(const struct HSV *hsv, uint len);

static void outputHSV(const struct HSV *hsv, uint len) {
	for (uint i = 0; i < len; ++i) {
		printf("%g,%g,%g\n", hsv[i].h, hsv[i].s, hsv[i].v);
	}
}

#define FORMAT_RGB "%02hhX%02hhX%02hhX"

static void outputRGB(const struct HSV *hsv, uint len) {
	for (uint i = 0; i < len; ++i) {
		struct RGB rgb = convert(hsv[i]);
		printf(FORMAT_RGB "\n", rgb.r, rgb.g, rgb.b);
	}
}

static void outputLinux(const struct HSV *hsv, uint len) {
	for (uint i = 0; i < len; ++i) {
		struct RGB rgb = convert(hsv[i]);
		printf("\x1B]P%X" FORMAT_RGB, i, rgb.r, rgb.g, rgb.b);
	}
}

static const char *Enum[SchemeLen] = {
	"DarkBlack", "DarkRed", "DarkGreen", "DarkYellow",
	"DarkBlue", "DarkMagenta", "DarkCyan", "DarkWhite",
	"LightBlack", "LightRed", "LightGreen", "LightYellow",
	"LightBlue", "LightMagenta", "LightCyan", "LightWhite",
	"Background", "Foreground", "Bold", "Selection", "Cursor",
};

static void outputEnum(const struct HSV *hsv, uint len) {
	printf("enum {\n");
	for (uint i = 0; i < len; ++i) {
		struct RGB rgb = convert(hsv[i]);
		printf("\t%s = 0x" FORMAT_RGB ",\n", Enum[i], rgb.r, rgb.g, rgb.b);
	}
	printf("};\n");
}

#define FORMAT_X "rgb:%02hhX/%02hhX/%02hhX"

static const char *Resources[SchemeLen] = {
	[Background] = "background",
	[Foreground] = "foreground",
	[Bold] = "colorBD",
	[Selection] = "highlightColor",
	[Cursor] = "cursorColor",
};

static void outputXTerm(const struct HSV *hsv, uint len) {
	for (uint i = 0; i < len; ++i) {
		struct RGB rgb = convert(hsv[i]);
		if (Resources[i]) {
			printf("XTerm*%s: " FORMAT_X "\n", Resources[i], rgb.r, rgb.g, rgb.b);
		} else {
			printf("XTerm*color%u: " FORMAT_X "\n", i, rgb.r, rgb.g, rgb.b);
		}
	}
}

static const char *Mintty[SchemeLen] = {
	"Black", "Red", "Green", "Yellow",
	"Blue", "Magenta", "Cyan", "White",
	"BoldBlack", "BoldRed", "BoldGreen", "BoldYellow",
	"BoldBlue", "BoldMagenta", "BoldCyan", "BoldWhite",
	[Background] = "BackgroundColour",
	[Foreground] = "ForegroundColour",
	[Cursor]     = "CursorColour",
};

static void outputMintty(const struct HSV *hsv, uint len) {
	for (uint i = 0; i < len; ++i) {
		if (!Mintty[i]) continue;
		struct RGB rgb = convert(hsv[i]);
		printf("%s=%hhu,%hhu,%hhu\n", Mintty[i], rgb.r, rgb.g, rgb.b);
	}
}

static void outputCSS(const struct HSV *hsv, uint len) {
	printf(":root {\n");
	for (uint i = 0; i < len; ++i) {
		struct RGB rgb = convert(hsv[i]);
		printf("\t--ansi%u: #" FORMAT_RGB ";\n", i, rgb.r, rgb.g, rgb.b);
	}
	printf("}\n");
	for (uint i = 0; i < len; ++i) {
		printf(
			".fg%u { color: var(--ansi%u); }\n"
			".bg%u { background-color: var(--ansi%u); }\n",
			i, i, i, i
		);
	}
}

enum {
	SwatchWidth = 64,
	SwatchHeight = 64,
	SwatchCols = 8,
};

static void outputPNG(const struct HSV *hsv, uint len) {
	uint rows = (len + SwatchCols - 1) / SwatchCols;
	uint width = SwatchWidth * SwatchCols;
	uint height = SwatchHeight * rows;
	pngHead(stdout, width, height, 8, PNGIndexed);

	struct RGB pal[len];
	for (uint i = 0; i < len; ++i) {
		pal[i] = convert(hsv[i]);
	}
	pngPalette(stdout, (byte *)pal, sizeof(pal));

	byte data[height][1 + width];
	memset(data, 0, sizeof(data));
	for (uint y = 0; y < height; ++y) {
		data[y][0] = (y % SwatchHeight ? PNGUp : PNGSub);
	}
	for (uint i = 0; i < len; ++i) {
		uint y = SwatchHeight * (i / SwatchCols);
		uint x = SwatchWidth * (i % SwatchCols);
		data[y][1 + x] = (x ? 1 : i);
	}
	pngData(stdout, (byte *)data, sizeof(data));
	pngTail(stdout);
}

int main(int argc, char *argv[]) {
	generate();

	OutputFn *output = outputRGB;
	const struct HSV *hsv = scheme;
	uint len = 16;

	int opt;
	while (0 < (opt = getopt(argc, argv, "Xacghilmp:stx"))) {
		switch (opt) {
			break; case 'X': output = outputXTerm;
			break; case 'a': len = 16;
			break; case 'c': output = outputEnum;
			break; case 'g': output = outputPNG;
			break; case 'h': output = outputHSV;
			break; case 'i': invert();
			break; case 'l': output = outputLinux;
			break; case 'm': output = outputMintty;
			break; case 'p': {
				uint p = strtoul(optarg, NULL, 0);
				if (p >= SchemeLen) return EX_USAGE;
				hsv = &scheme[p];
				len = 1;
			}
			break; case 's': output = outputCSS;
			break; case 't': len = SchemeLen;
			break; case 'x': output = outputRGB;
			break; default:  return EX_USAGE;
		}
	}

	output(hsv, len);
}