HSL to RGB converter - useful for graphics!

[loudar]

Hey!

Used this for a while and I think I've fixed every major bug, if you happen to have improvements I'll take them :D Give it a hue, saturation, lightness and alpha and you can read out the R, G and B values if you need to, but works nice just to shift things in color or whatever. Have fun!

Code: QB64: [Select]

1. '-------------------------------- DEMO --------------------------------'
2.  
3. SCREEN _NEWIMAGE(1000, 500, 32)
4.  
5. 'definitions
6. h = 0 'takes values from 0 to 359
7. s = 1 'takes values from 0 to 1
8. l = 1 'takes values from 0 to 1
9. changepercycle = 5
10.  
11. DO
12.     h = h + changepercycle 'changes the hue each loop
13.     keyhit = _KEYHIT
14.  
15.     colour& = hsltorgb~&(h, s, l, 255)
16.     COLOR colour&
17.     PRINT h, s, l, "HSL", _RED(colour&), _GREEN(colour&), _BLUE(colour&), "RGB"
18.     _LIMIT 60
19. LOOP UNTIL keyhit = 13
20.  
21. SLEEP
22. SYSTEM
23.  
24. '-------------------------------- DEMO --------------------------------'
25.  
26. FUNCTION hr& (hue AS _FLOAT, saturation AS _FLOAT, lightness AS _FLOAT)
27.     SELECT CASE hue
28.         CASE IS < 60 AND hue >= 0: tr = 1
29.         CASE IS < 120 AND hue >= 60: tr = 1 - ((hue - 60) / 60)
30.         CASE IS < 180 AND hue >= 120: tr = 0
31.         CASE IS < 240 AND hue >= 180: tr = 0
32.         CASE IS < 300 AND hue >= 240: tr = (hue - 240) / 60
33.         CASE IS < 360 AND hue >= 300: tr = 1
34.     END SELECT
35.     hr& = tr * 255
36. END FUNCTION
37.  
38. FUNCTION hg& (hue AS _FLOAT, saturation AS _FLOAT, lightness AS _FLOAT)
39.     SELECT CASE hue
40.         CASE IS < 60 AND hue >= 0: tg = hue / 60
41.         CASE IS < 120 AND hue >= 60: tg = 1
42.         CASE IS < 180 AND hue >= 120: tg = 1
43.         CASE IS < 240 AND hue >= 180: tg = 1 - ((hue - 180) / 60)
44.         CASE IS < 300 AND hue >= 240: tg = 0
45.         CASE IS < 360 AND hue >= 300: tg = 0
46.     END SELECT
47.     hg& = tg * 255
48. END FUNCTION
49.  
50. FUNCTION hb& (hue AS _FLOAT, saturation AS _FLOAT, lightness AS _FLOAT)
51.     SELECT CASE hue
52.         CASE IS < 60 AND hue >= 0: tb = 0
53.         CASE IS < 120 AND hue >= 60: tb = 0
54.         CASE IS < 180 AND hue >= 120: tb = (hue - 120) / 60
55.         CASE IS < 240 AND hue >= 180: tb = 1
56.         CASE IS < 300 AND hue >= 240: tb = 1
57.         CASE IS < 360 AND hue >= 300: tb = 1 - ((hue - 300) / 60)
58.     END SELECT
59.     hb& = tb * 255
60. END FUNCTION
61.  
62. FUNCTION hsltorgb~& (conH, conS, conL, conA)
63.     IF conH >= 360 THEN conH = (conH MOD 360) * 360
64.     IF conS > 1 THEN conS = 1
65.     IF conL > 1 THEN conL = 1
66.  
67.     objR = hr&(conH, conS, conL) * conS
68.     objG = hg&(conH, conS, conL) * conS
69.     objB = hb&(conH, conS, conL) * conS
70.  
71.     'maximizing to full 255
72.     IF objR >= objG AND objG >= objB THEN '123
73.         factor = 255 / objR
74.     ELSEIF objG >= objR AND objR >= objB THEN '213
75.         factor = 255 / objG
76.     ELSEIF objB >= objR AND objR >= objG THEN '312
77.         factor = 255 / objB
78.     ELSEIF objR >= objB AND objB >= objG THEN '132
79.         factor = 255 / objR
80.     ELSEIF objG >= objB AND objB >= objR THEN '231
81.         factor = 255 / objG
82.     ELSEIF objB >= objR AND objG >= objR THEN '321
83.         factor = 255 / objB
84.     END IF
85.     objR = objR * factor
86.     objG = objG * factor
87.     objB = objB * factor
88.  
89.     'adjusting to lightness
90.     objR = objR * conL
91.     objG = objG * conL
92.     objB = objB * conL
93.  
94.     'adjusting to saturation
95.     IF objR = 0 OR objG = 0 OR objB = 0 THEN
96.         objavg = (objR + objG + objB) / 2
97.     ELSE
98.         objavg = (objR + objG + objB) / 3
99.     END IF
100.     IF conS > 0.1 THEN
101.         objR = objR + ((objavg - objR) * (1 - conS))
102.         objG = objG + ((objavg - objG) * (1 - conS))
103.         objB = objB + ((objavg - objB) * (1 - conS))
104.     ELSE
105.         objR = objavg
106.         objG = objavg
107.         objB = objavg
108.     END IF
109.  
110.     hsltorgb~& = _RGBA(objR, objG, objB, conA)
111. END FUNCTION

[bplus]

Always liked rainbow text :)

Kind of curious where we run into HSL values in QB64?

[loudar]

I don't really know where it appears natively, but it's really useful if you have a color and want to shift it by a certain degree. Can't really do that in RGB, so an HSL->RGB function is kind of necessary when working with graphics on a more specific level. I guess there's stuff that you can import that don't really need that (there was a color picker somewhere in the forum which I guess has a conversion already?) but I wrote my own for convenience and learning, so figured I'd share it anyway :D

[bplus]

Yeah, it would be handy to cycle through all colors by just changing 1 number the h for hue I assume.

And then add lightness or darkness the l for light, maybe?

But what is saturation s? something with alpha or transparencies?

[loudar]

Saturation moves the R, G and B values closer to the average between them the smaller the value is. It's nice if you want to have things just white/grey/black or just desaturated! Can't guarantee that's the proper algorithm for it, just wanted to somehow implement it.

[bplus]

Yeah I am not seeing any work with alpha, it's just being passed through to RGBA function without change.

[SMcNeill]

Doesn’t Rhosigma’s libraries include a convertor for this?  I’m thinking it does.  If so, you might want to compare ideas and see how he does his.  ;)

[bplus]

Here is bunch of things to compare: https://www.qb64.org/forum/index.php?topic=2173.msg114193#msg114193

I bet I will see Loudar's in action in AVAR when I get to it.

[RhoSigma]

Doesn’t Rhosigma’s libraries include a convertor for this?  I’m thinking it does.  If so, you might want to compare ideas and see how he does his.  ;)

The converthelper.bm file in my libaries collection (IMG-Support folder) has functions for the HSB/HSV color model, according to Wikipedia there's a difference between HSB/HSV and HSL, although the models are very similar.

here's a good description:
https://medium.com/innovaccer-tech/rgb-vs-hsb-vs-hsl-demystified-1992d7273d3a

The essence in this article is:

Hence, the only difference is that in HSB, 100% Brightness can give you the White Colour only when the Saturation is 0 while in HSL 100% Lightness will give you the White Colour irrespective of the Saturation.