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198 | #include "panel-color.h"
/**
* rgb_to_hls:
* @r: on input, red; on output, hue
* @g: on input, green; on output, lightness
* @b: on input, blue; on output, saturation
*
* Converts a red/green/blue triplet to a hue/lightness/saturation triplet.
*/
static void
rgb_to_hls (gdouble *r, gdouble *g, gdouble *b)
{
gdouble min;
gdouble max;
gdouble red;
gdouble green;
gdouble blue;
gdouble h, l, s;
gdouble delta;
red = *r;
green = *g;
blue = *b;
if (red > green) {
if (red > blue)
max = red;
else
max = blue;
if (green < blue)
min = green;
else
min = blue;
} else {
if (green > blue)
max = green;
else
max = blue;
if (red < blue)
min = red;
else
min = blue;
}
l = (max + min) / 2;
s = 0;
h = 0;
if (max != min) {
if (l <= 0.5)
s = (max - min) / (max + min);
else
s = (max - min) / (2 - max - min);
delta = max -min;
if (red == max)
h = (green - blue) / delta;
else if (green == max)
h = 2 + (blue - red) / delta;
else if (blue == max)
h = 4 + (red - green) / delta;
h *= 60;
if (h < 0.0)
h += 360;
}
*r = h;
*g = l;
*b = s;
}
/**
* hls_to_rgb:
* @h: on input, hue; on output, red
* @l: on input, lightness; on output, green
* @s: on input, saturation; on output, blue
*
* Converts a hue/lightness/saturation triplet to a red/green/blue triplet.
*/
static void
hls_to_rgb (gdouble *h, gdouble *l, gdouble *s)
{
gdouble hue;
gdouble lightness;
gdouble saturation;
gdouble m1, m2;
gdouble r, g, b;
lightness = *l;
saturation = *s;
if (lightness <= 0.5)
m2 = lightness * (1 + saturation);
else
m2 = lightness + saturation - lightness * saturation;
m1 = 2 * lightness - m2;
if (saturation == 0) {
*h = lightness;
*l = lightness;
*s = lightness;
} else {
hue = *h + 120;
while (hue > 360)
hue -= 360;
while (hue < 0)
hue += 360;
if (hue < 60)
r = m1 + (m2 - m1) * hue / 60;
else if (hue < 180)
r = m2;
else if (hue < 240)
r = m1 + (m2 - m1) * (240 - hue) / 60;
else
r = m1;
hue = *h;
while (hue > 360)
hue -= 360;
while (hue < 0)
hue += 360;
if (hue < 60)
g = m1 + (m2 - m1) * hue / 60;
else if (hue < 180)
g = m2;
else if (hue < 240)
g = m1 + (m2 - m1) * (240 - hue) / 60;
else
g = m1;
hue = *h - 120;
while (hue > 360)
hue -= 360;
while (hue < 0)
hue += 360;
if (hue < 60)
b = m1 + (m2 - m1) * hue / 60;
else if (hue < 180)
b = m2;
else if (hue < 240)
b = m1 + (m2 - m1) * (240 - hue) / 60;
else
b = m1;
*h = r;
*l = g;
*s = b;
}
}
/**
* ctk_style_shade:
* @a: the starting colour
* @b: (out): the resulting colour
* @k: amount to scale lightness and saturation by
*
* Takes a colour "a", scales the lightness and saturation by a certain amount,
* and sets "b" to the resulting colour.
* ctkstyle.c cut-and-pastage.
*/
void
ctk_style_shade (CdkRGBA *a, CdkRGBA *b, gdouble k)<--- Parameter 'a' can be declared as pointer to const
{
gdouble red;
gdouble green;
gdouble blue;
red = a->red;
green = a->green;
blue = a->blue;
rgb_to_hls (&red, &green, &blue);
green *= k;
if (green > 1.0)
green = 1.0;
else if (green < 0.0)
green = 0.0;
blue *= k;
if (blue > 1.0)
blue = 1.0;
else if (blue < 0.0)
blue = 0.0;
hls_to_rgb (&red, &green, &blue);
b->red = red;
b->green = green;
b->blue = blue;
}
|