Atari 800XL Palette

This palette is based on values in an actual Atari 800 emulator available from Sourceforge.

63	77	91	106	121	135	151	161	175	190	206	219	235	250	255
															0	Grey
															1	Gold
															2	Orange
															3	Red-Orange
															4	Pink
															5	Purple
															6	Purple-Blue
															7	Blue
															8	Blue
															9	Light Blue
															10	Turquoise
															11	Green- Blue
															12	Green
															13	Yellow-Green
															14	Orange-Green
															15	Light Orange

static const double redf   = 0.30;
static const double greenf = 0.59;
static const double bluef  = 0.11;

static void Palette_Format(int black, int white, int colors)
/* format loaded palette */
{
  double white_in, black_in, brightfix;
  pal_t rgb;
  int i, j;

  for (i = 0; i <0x100; i++) { int c="basicpal[i];" rgb[i].r="(c">> 16) & 0xff;
    rgb[i].g = (c >> 8) & 0xff;
    rgb[i].b = c & 0xff;
  }

  black_in = redf * rgb[ 0].r + greenf * rgb[ 0].g + bluef * rgb[ 0].b;
  white_in = redf * rgb[15].r + greenf * rgb[15].g + bluef * rgb[15].b;
  brightfix = (double)(white - black) / (white_in - black_in);

  for (i = 0; i < 0x10; i++)
  {
    for (j = 0; j < 0x10; j++)
    {
      double y, r, g, b;
      int r1, g1, b1;

	// y is luminance, easy to calculate
      y = redf   * rgb[i * 16 + j].r
	+ greenf * rgb[i * 16 + j].g
	+ bluef  * rgb[i * 16 + j].b;
      r = (double)rgb[i * 16 + j].r - y;
      g = (double)rgb[i * 16 + j].g - y;
      b = (double)rgb[i * 16 + j].b - y;

      y = ((y - black_in) * brightfix) + black;
      r *= (double)colors * brightfix / (double)COLINTENS;
      g *= (double)colors * brightfix / (double)COLINTENS;
      b *= (double)colors * brightfix / (double)COLINTENS;

      r1 = y + r;
      g1 = y + g;
      b1 = y + b;

      CLIP_VAR(r1);
      CLIP_VAR(g1);
      CLIP_VAR(b1);

      rgb[i * 16 + j].r = r1;
      rgb[i * 16 + j].g = g1;
      rgb[i * 16 + j].b = b1;
    }
  }

  for (i = 0; i < 0x100; i++)
  {
    colortable[i] = (rgb[i].r << 16) + (rgb[i].g << 8) + (rgb[i].b << 0);
  }