/* Copies the loaded external palette into current palette - without applying
adjustments. */
static void CopyExternalWithoutAdjustments(void)
{
int i;
unsigned char *ext_ptr;
for (i = 0, ext_ptr = Colours_external->palette; i < 256; i ++, ext_ptr += 3)
Colours_SetRGB(i, *ext_ptr, *(ext_ptr + 1), *(ext_ptr + 2), Colours_table);
}
/* Applies the colours setup to the external palette. Writes output to
COLOURTABLE. */
static void AdjustExternal(int colourtable[256])
{
const double gamma = 1 - COLOURS_PAL_setup.gamma / 2.0;
unsigned char *ext_ptr = COLOURS_PAL_external.palette;
int n;
for (n = 0; n < 256; n ++) {
/* Convert RGB values from external palette to YIQ. */
double r = (double)*ext_ptr++ / 255.0;
double g = (double)*ext_ptr++ / 255.0;
double b = (double)*ext_ptr++ / 255.0;
double y = 0.299 * r + 0.587 * g + 0.114 * b;
double u = -0.14713 * r - 0.28886 * g + 0.436 * b;
double v = 0.615 * r - 0.51499 * g - 0.10001 * b;
y = pow(y, gamma);
y *= COLOURS_PAL_setup.contrast * 0.5 + 1;
y += COLOURS_PAL_setup.brightness * 0.5;
if (y > 1.0)
y = 1.0;
else if (y < 0.0)
y = 0.0;
u *= COLOURS_PAL_setup.saturation + 1.0;
v *= COLOURS_PAL_setup.saturation + 1.0;
r = y + 1.13983 * v;
g = y - 0.39465 * u - 0.58060 * v;
b = y + 2.03211 * u;
Colours_SetRGB(n, (int) (r * 255), (int) (g * 255), (int) (b * 255), colourtable);
}
}
/* Averages YUV values from YUV_TABLE and converts them to RGB values. Stores
them in COLOURTABLE. */
static void YUV2RGB(int colourtable[256], double const yuv_table[256*5])
{
double const *yuv_ptr = yuv_table;
int n;
for (n = 0; n < 256; ++n) {
double y = *yuv_ptr++;
double even_u = *yuv_ptr++;
double odd_u = *yuv_ptr++;
double even_v = *yuv_ptr++;
double odd_v = *yuv_ptr++;
double r, g, b;
/* The different colors in odd and even lines are not
emulated - instead the palette contains averaged values. */
double u = (even_u + odd_u) / 2.0;
double v = (even_v + odd_v) / 2.0;
Colours_YUV2RGB(y, u, v, &r, &g, &b);
if (!COLOURS_PAL_external.loaded || COLOURS_PAL_external.adjust) {
/* The r, g, b values derived from the YUV signal are non-linear
(ie. gamma-corrected). We convert them to linear values,
assuming the CRT TV's gamma = COLOURS_PAL_setup.gamma. */
r = Colours_Gamma2Linear(r, COLOURS_PAL_setup.gamma);
g = Colours_Gamma2Linear(g, COLOURS_PAL_setup.gamma);
b = Colours_Gamma2Linear(b, COLOURS_PAL_setup.gamma);
/* Now we convert the linear values to the sRGB colourspace. */
r = Colours_Linear2sRGB(r);
g = Colours_Linear2sRGB(g);
b = Colours_Linear2sRGB(b);
}
Colours_SetRGB(n, (int) (r * 255), (int) (g * 255), (int) (b * 255), colourtable);
}
}
/* Generates a PAL palette, based on colour setup. Result is written into
COLOURTABLE. */
static void GeneratePalette(int colourtable[256])
{
int cr, lm;
double scaled_black_level = (double)COLOURS_PAL_setup.black_level / 255.0f;
double scaled_white_level = (double)COLOURS_PAL_setup.white_level / 255.0f;
const double gamma = 1 - COLOURS_PAL_setup.gamma / 2.0;
/* NTSC luma multipliers from CGIA.PDF */
double luma_mult[16] = {
0.6941, 0.7091, 0.7241, 0.7401,
0.7560, 0.7741, 0.7931, 0.8121,
0.8260, 0.8470, 0.8700, 0.8930,
0.9160, 0.9420, 0.9690, 1.0000};
/* TODO Angles were chosen based on examination of several
PAL screenshots. A thorough examination of PAL GTIA color
generation is needed instead, to determine a mathematical formula
that stands behind these values. */
double color_angles[16] = {
0.0, 2.267095, 1.927638, 1.715966,
1.228852, 0.863367, 0.447344, -0.361837,
-0.815415, -1.198193, 4.568137, 4.014433,
3.568811, 3.134938, 2.71825, 2.279574
};
for (cr = 0; cr < 16; cr ++) {
double angle = color_angles[cr];
double saturation = (cr ? (COLOURS_PAL_setup.saturation + 1) * 0.175f: 0.0f);
double u = cos(angle) * saturation;
double v = sin(angle) * saturation;
for (lm = 0; lm < 16; lm ++) {
/* calculate yiq for color entry */
double y = (luma_mult[lm] - luma_mult[0]) / (luma_mult[15] - luma_mult[0]);
double r, g, b;
y = pow(y, gamma);
y *= COLOURS_PAL_setup.contrast * 0.5 + 1;
y += COLOURS_PAL_setup.brightness * 0.5;
/* Scale the Y signal's range from 0..1 to
* scaled_black_level..scaled_white_level */
y = y * (scaled_white_level - scaled_black_level) + scaled_black_level;
/*
if (y < scaled_black_level)
y = scaled_black_level;
else if (y > scaled_white_level)
y = scaled_white_level;
*/
r = y + 1.13983 * v;
g = y - 0.39465 * u - 0.58060 * v;
b = y + 2.03211 * u;
Colours_SetRGB(cr * 16 + lm, (int) (r * 255), (int) (g * 255), (int) (b * 255), colourtable);
}
}
}
