sixel: add HLS color format support

meson.build

@@ -118,6 +118,7 @@ executable(
   'server.c', 'server.h',
   'shm.c', 'shm.h',
   'sixel.c', 'sixel.h',
+  'sixel-hls.c', 'sixel-hls.h',
   'slave.c', 'slave.h',
   'terminal.c', 'terminal.h',
   'tokenize.c', 'tokenize.h',

sixel-hls.c

@@ -0,0 +1,117 @@
+// sixel.c (part of mintty)
+// this function is derived from a part of graphics.c
+// in Xterm pl#310 originally written by Ross Combs.
+//
+// Copyright 2013,2014 by Ross Combs
+//
+//                         All Rights Reserved
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+// IN NO EVENT SHALL THE ABOVE LISTED COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
+// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+// Except as contained in this notice, the name(s) of the above copyright
+// holders shall not be used in advertising or otherwise to promote the
+// sale, use or other dealings in this Software without prior written
+// authorization.
+
+#include "sixel-hls.h"
+
+#define SIXEL_RGB(r, g, b) (((r) << 16) + ((g) << 8) +  (b))
+
+int
+hls_to_rgb(int hue, int lum, int sat)
+{
+    double hs = (hue + 240) % 360;
+    double hv = hs / 360.0;
+    double lv = lum / 100.0;
+    double sv = sat / 100.0;
+    double c, x, m, c2;
+    double r1, g1, b1;
+    int r, g, b;
+    int hpi;
+
+    if (sat == 0) {
+        r = g = b = lum * 255 / 100;
+        return SIXEL_RGB(r, g, b);
+    }
+
+    if ((c2 = ((2.0 * lv) - 1.0)) < 0.0) {
+        c2 = -c2;
+    }
+    c = (1.0 - c2) * sv;
+    hpi = (int) (hv * 6.0);
+    x = (hpi & 1) ? c : 0.0;
+    m = lv - 0.5 * c;
+
+    switch (hpi) {
+    case 0:
+        r1 = c;
+        g1 = x;
+        b1 = 0.0;
+        break;
+    case 1:
+        r1 = x;
+        g1 = c;
+        b1 = 0.0;
+        break;
+    case 2:
+        r1 = 0.0;
+        g1 = c;
+        b1 = x;
+        break;
+    case 3:
+        r1 = 0.0;
+        g1 = x;
+        b1 = c;
+        break;
+    case 4:
+        r1 = x;
+        g1 = 0.0;
+        b1 = c;
+        break;
+    case 5:
+        r1 = c;
+        g1 = 0.0;
+        b1 = x;
+        break;
+    default:
+        return SIXEL_RGB(255, 255, 255);
+    }
+
+    r = (int) ((r1 + m) * 100.0 + 0.5);
+    g = (int) ((g1 + m) * 100.0 + 0.5);
+    b = (int) ((b1 + m) * 100.0 + 0.5);
+
+    if (r < 0) {
+        r = 0;
+    } else if (r > 100) {
+        r = 100;
+    }
+    if (g < 0) {
+        g = 0;
+    } else if (g > 100) {
+        g = 100;
+    }
+    if (b < 0) {
+        b = 0;
+    } else if (b > 100) {
+        b = 100;
+    }
+    return SIXEL_RGB(r * 255 / 100, g * 255 / 100, b * 255 / 100);
+}

sixel-hls.h

@@ -0,0 +1,9 @@
+#pragma once
+
+/*
+ * Primary color hues:
+ *  blue:  0 degrees
+ *  red:   120 degrees
+ *  green: 240 degrees
+ */
+int hls_to_rgb(int hue, int lum, int sat);

sixel.c

@@ -6,6 +6,7 @@
 #define LOG_ENABLE_DBG 0
 #include "log.h"
 #include "render.h"
+#include "sixel-hls.h"
 
 #define ALEN(v) (sizeof(v) / sizeof(v[0]))
 #define max(x, y) ((x) > (y) ? (x) : (y))
@@ -346,8 +347,10 @@ decgci(struct terminal *term, uint8_t c)
 
             switch (format) {
             case 1: { /* HLS */
-                LOG_ERR("HLS color format not implemented");
-                assert(false && "HLS color format not implemented");
+                uint32_t rgb = hls_to_rgb(c1, c2, c3);
+                LOG_DBG("setting palette #%d = HLS %hhu/%hhu/%hhu (0x%06x)",
+                        term->sixel.color_idx, c1, c2, c3, rgb);
+                term->sixel.palette[term->sixel.color_idx] = rgb;
                 break;
             }