Add color scheme PNG generator

1 files changed, 136 insertions, 0 deletions

diff --git a/bin/scheme.c b/bin/scheme.c
new file mode 100644
index 00000000..f1b12eae
--- /dev/null
+++ b/bin/scheme.c
@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2018  Curtis 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 <arpa/inet.h>
+#include <err.h>
+#include <math.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sysexits.h>
+#include <zlib.h>
+
+struct Hsv {
+    double h, s, v;
+};
+
+struct Rgb {
+    uint8_t r, g, b;
+};
+
+static struct Rgb toRgb(struct Hsv hsv) {
+    double c = hsv.v * hsv.s;
+    double h = hsv.h / 60.0;
+    double x = c * (1.0 - fabs(fmod(h, 2.0) - 1.0));
+    double m = hsv.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 uint32_t crc;
+static void pngWrite(const void *ptr, size_t size) {
+    fwrite(ptr, size, 1, stdout);
+    if (ferror(stdout)) err(EX_IOERR, "(stdout)");
+    crc = crc32(crc, ptr, size);
+}
+static void pngInt(uint32_t host) {
+    uint32_t net = htonl(host);
+    pngWrite(&net, 4);
+}
+static void pngChunk(const char *type, uint32_t size) {
+    pngInt(size);
+    crc = crc32(0, Z_NULL, 0);
+    pngWrite(type, 4);
+}
+enum { NONE, SUB, UP, AVERAGE, PAETH };
+
+static void png(const struct Hsv *hsv, uint8_t len) {
+    uint32_t swatchWidth = 64;
+    uint32_t swatchHeight = 64;
+    uint32_t columns = 8;
+    uint32_t rows = (len + columns - 1) / columns;
+    uint32_t width = swatchWidth * columns;
+    uint32_t height = swatchHeight * rows;
+
+    pngWrite("\x89PNG\r\n\x1A\n", 8);
+
+    pngChunk("IHDR", 13);
+    pngInt(width);
+    pngInt(height);
+    pngWrite("\x08\x03\0\0\0", 5);
+    pngInt(crc);
+
+    pngChunk("PLTE", 3 * len);
+    for (uint8_t i = 0; i < len; ++i) {
+        struct Rgb rgb = toRgb(hsv[i]);
+        pngWrite(&rgb, 3);
+    }
+    pngInt(crc);
+
+    uint8_t data[height][1 + width];
+    memset(data, 0, sizeof(data));
+    for (uint32_t y = 0; y < height; ++y) {
+        data[y][0] = (y % swatchHeight) ? UP : SUB;
+    }
+    for (uint8_t i = 0; i < len; ++i) {
+        uint32_t y = swatchHeight * (i / columns);
+        uint32_t x = swatchWidth * (i % columns);
+        data[y][1 + x] = x ? 1 : i;
+    }
+
+    uLong size = compressBound(sizeof(data));
+    uint8_t deflate[size];
+    int error = compress(deflate, &size, (Byte *)data, sizeof(data));
+    if (error != Z_OK) errx(EX_SOFTWARE, "compress: %d", error);
+
+    pngChunk("IDAT", size);
+    pngWrite(deflate, size);
+    pngInt(crc);
+
+    pngChunk("IEND", 0);
+    pngInt(crc);
+}
+
+int main() {
+    struct Hsv scheme[16] = {
+        { 0.0,   1.0, 1.0 },
+        { 45.0,  1.0, 1.0 },
+        { 90.0,  1.0, 1.0 },
+        { 135.0, 1.0, 1.0 },
+        { 180.0, 1.0, 1.0 },
+        { 225.0, 1.0, 1.0 },
+        { 270.0, 1.0, 1.0 },
+        { 315.0, 1.0, 1.0 },
+        { 0.0,   0.5, 1.0 },
+        { 45.0,  0.5, 1.0 },
+        { 90.0,  0.5, 1.0 },
+        { 135.0, 0.5, 1.0 },
+        { 180.0, 0.5, 1.0 },
+        { 225.0, 0.5, 1.0 },
+        { 270.0, 0.5, 1.0 },
+        { 315.0, 0.5, 1.0 },
+    };
+    png(scheme, 16);
+    return EX_OK;
+}