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hsl: add our own implementations of rgb-to-hsl and hsl-to-rgb

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* New function: rgb_to_hsl()
* New function: hsl_to_rgb()
* Replace XTerm’s hls_to_rgb() with our own, hsl_to_rgb().
* Ensure hue/lum/sat values are within range before calling
  hsl_to_rgb()

Note that sixels’ use the following primary hues:

*  blue:  0°
*  red:   120
*  green: 240°

While “standard” HSL uses:

*  red:   0°
*  green: 120°
*  blue:  240°

Thus, we need to adjust the sixel’s hue value before calling
hsl_to_rgb().
This commit is contained in:
Daniel Eklöf 2020-11-15 19:45:33 +01:00
parent 8e779b356e
commit e0297daa1f
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GPG key ID: 5BBD4992C116573F
6 changed files with 124 additions and 136 deletions
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37
sixel.c
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@ -7,7 +7,7 @@
#define LOG_ENABLE_DBG 0
#include "log.h"
#include "render.h"
#include "sixel-hls.h"
#include "hsl.h"
#include "util.h"
#include "xmalloc.h"
@ -1052,23 +1052,42 @@ decgci(struct terminal *term, uint8_t c)
if (nparams > 4) {
unsigned format = term->sixel.params[1];
unsigned c1 = term->sixel.params[2];
unsigned c2 = term->sixel.params[3];
unsigned c3 = term->sixel.params[4];
int c1 = term->sixel.params[2];
int c2 = term->sixel.params[3];
int c3 = term->sixel.params[4];
switch (format) {
case 1: { /* HLS */
uint32_t rgb = hls_to_rgb(c1, c2, c3);
int hue = min(c1, 360);
int lum = min(c2, 100);
int sat = min(c3, 100);
/*
* Sixel’s HLS use the following primary color hues:
* blue: 0°
* red: 120°
* green: 240°
*
* While “standard” HSL uses:
* red: 0°
* green: 120°
* blue: 240°
*/
hue = (hue + 240) % 360;
uint32_t rgb = hsl_to_rgb(hue, sat, lum);
LOG_DBG("setting palette #%d = HLS %hhu/%hhu/%hhu (0x%06x)",
term->sixel.color_idx, c1, c2, c3, rgb);
term->sixel.color_idx, hue, lum, sat, rgb);
term->sixel.palette[term->sixel.color_idx] = rgb;
break;
}
case 2: { /* RGB */
uint8_t r = 255 * c1 / 100;
uint8_t g = 255 * c2 / 100;
uint8_t b = 255 * c3 / 100;
uint8_t r = 255 * min(c1, 100) / 100;
uint8_t g = 255 * min(c2, 100) / 100;
uint8_t b = 255 * min(c3, 100) / 100;
LOG_DBG("setting palette #%d = RGB %hhu/%hhu/%hhu",
term->sixel.color_idx, r, g, b);