Ok, so clear explanation of ShiftColorValue function
newcolor% = ShiftColorValue ( oldcolor%, brightness%, saturation%, hue% )
The variable newcolor is given a value in RGBA calculated from oldcolor according to settings brightness, saturation and hue.
brightness can be given values from 0 to 200. 0 is totally black. 200 is totally white. 100 is normal brightness.
saturation can be given values from 0 to 200. 0 is totally colourless - black & white. 200 is maximum saturation. 100 is normal saturation. Be careful using values above 100. While this can work well much of the time it can produce odd results in some sprites when brightness is over 100.
hue can be given values from 0 to 359. 0 is no change whatsoever. 180 results in the complete opposite colour.
FUNCTION ShiftColorValue: color, bri, sat, hue
// color is the original color to change according to the following values:-
// bri = brightness. Can be 0 to 100 to 200. 0 = total darkness. 100 = normal light. over 100 you'll get a bleached look - "over" brightness
// sat = saturation. Can be 0 to 100 to 200. 0 = black & white. 100 = normal saturation. over 100 is "over" saturation. More colourful.
// hue = hue shift. Can be 0 to 359. 0 is no change.
LOCAL hu, cmax%, cmin%, diff, r%, g%, b%, a%, tmin%, tdiff%
a = bAND(ASR(color,24),0xff)
IF a = 0
RETURN color
ELSE
r = bAND(color,0xff)
g = bAND(ASR(color,8),0xff)
b = bAND(ASR(color,16),0xff)
cmax = MAX(b,MAX(r,g))
cmin = MIN(b,MIN(r,g))
diff = cmax-cmin
// hue calculations - hu = hue of color%
IF hue <> 0
IF r > g
IF g > b // 7 Between red and yellow
hu = ((g-b)/diff)*60
ELSEIF b > g
IF b = r
hu = 300 // Pure Magnenta
ELSE
hu = 300 + ((r-b)/diff)*60 // 12 Between Magnenta and Red
ENDIF
ELSE // g = b
hu = 0 // 1 Pure Red
ENDIF
ELSEIF g > b
IF b > r // 9 Between green and cyan
hu = 120 + ((b-r)/diff)*60
ELSEIF r > b // 8 Between yellow and green
IF r = g // Pure Yellow
hu = 60
ELSE
hu = 60 + ((g-r)/diff)*60 // 8 Between yellow and green
ENDIF
ELSE // b = r
hu = 120 // 3 Pure green
ENDIF
ELSE // b > r
IF r > g // 11 Between blue and magnenta
hu = 240 + ((r-g)/diff)*60
ELSEIF g > r
IF g = b // Pure Cyan
hu = 180
ELSE
hu = 180 + ((b-g)/diff)*60 // 10 Between cyan and blue
ENDIF
ELSE // r = g
hu = hu = 240 // 5 Pure blue
ENDIF
ENDIF
// Adjust hue
hue = hue + hu
IF hue >= 360 THEN DEC hue, 360
IF hue > 0 AND hue < 60 // Between red and yellow
r = cmax
b = cmin
g = cmin+(hue*(diff/60))
ELSEIF hue > 60 AND hue < 120 // Between Yellow and green
g = cmax
b = cmin
r = cmax-((hue-60)*(diff/60))
ELSEIF hue > 120 AND hue < 180 // Between green and cyan
g = cmax
r = cmin
b = cmin+((hue-120)*(diff/60))
ELSEIF hue > 180 AND hue < 240 // Between cyan and blue
b = cmax
r = cmin
g = cmax-((hue-180)*(diff/60))
ELSEIF hue > 240 AND hue < 300 // Betweeen blue and magnenta
b = cmax
g = cmin
r = cmin+((hue-240)*(diff/60))
ELSEIF hue > 300 // Between mangenta and red
r = cmax
g = cmin
b = cmax-((hue-300)*(diff/60))
ELSEIF hue = 0 // Pure Red
r = cmax
g = cmin
b = cmin
ELSEIF hue = 60 // Pure Yellow
r = cmax
g = cmax
b = cmin
ELSEIF hue = 120 // Pure Green
r = cmin
g = cmax
b = cmin
ELSEIF hue = 180 // Pure Cyan
r = cmin
g = cmax
b = cmax
ELSEIF hue = 240 // Pure Blue
r = cmin
g = cmin
b = cmax
ELSEIF hue = 300 // Pure magnenta
r = cmax
g = cmin
b = cmax
ENDIF
ENDIF
// Adjust saturation
IF sat <> 100
sat = 100-sat
IF r <> cmax
tmin = r
tdiff = cmax - tmin
r = tmin + tdiff*(sat/100)
ENDIF
IF g <> cmax
tmin = g
tdiff = cmax - tmin
g = tmin + tdiff*(sat/100)
ENDIF
IF b <> cmax
tmin = b
tdiff = cmax - tmin
b = tmin + tdiff*(sat/100)
ENDIF
ENDIF
// Adjust brightness
IF bri <> 100
IF bri = 0
r = 0
g = 0
b = 0
ELSE
DEC r, (100-bri)*2.55
DEC g, (100-bri)*2.55
DEC b, (100-bri)*2.55
ENDIF
ENDIF
IF r < 0 THEN r = 0
IF r > 255 THEN r = 255
IF g < 0 THEN g = 0
IF g > 255 THEN g = 255
IF b < 0 THEN b = 0
IF b > 255 THEN b = 255
RETURN bOR(RGB(r,g,b), ASL(a, 24))
ENDIF
ENDFUNCTION
