Comes from: http://www.paris-pc-gis.com/mi_enviro/colors/color_models.htm#6-4 R , G , B <> H , S , lor : http://130.113.54.154/~monger/hsl-rgb.html
RGB> HSL
1 - Convert the RBG VALUES TO The Range 0-1
Example: from The Video Colors Page, ColorBar Red Has r = 83%, B = 7%, G = 7%, or in this scale, r = .83, b = .07, g = .07
2 - Find min and max values of r, b, g
In the example, maxcolor = .83, mincolor = .07
3 - l = (MaxColor MinColor) / 2
For the example, l = (.83 .07) / 2 = .45
4 - IF The max and min colors areic (I.E. The Color Is Some Kind of Grey), S Is Defined To BE 0, And H IS undefined But in Programs Usually Written As 0. (All IS DONE)
5 - OtherWise, Test L.
IF L <0.5, S = (MaxColor-minColor) / (MaxColor Mincolor)
IF L> = 0.5, s = (MaxColor-minColor) / (2.0-maxColor-minColor)
FOR THE EXAMPLE, L = 0.45 SO S = (. 83-.07) / (. 83 .07) = .84
6 - Compute
IF r = maxcolor, h = (g-b) / (maxColor-mincolor)
IF g = maxcolor, h = 2.0 (b-r) / (maxColor-mincolor)
IF B = MaxColor, H = 4.0 (R-G) / (MaxColor-minColor)
For THE EXAMPLE, R = MaxColor SO H = (. 83-.07) = 0
7 - To Use the Scaling Shown in The Video Color Page, Convert L and S Back to Percentages, And H Into An Angle in Degrees (IE Scale IT from 0-360).
8 - From The Computation in Step 6, H Will Range from 0-6. RGB Space IS A Cube, And HSL Space IS A Double Hexacone, WHERE L Is The Principal Diagonal of The RGB Cube. Thus Corners of the RGB Cube; Red , YELLOW, GREEN, CYAN, Blue, And Magenta, Become The Vertices of The HSL Hexagon. The value 0-6 for h tells you which section of the hexagon you are in. h Is Most Commonly Given As in Degrees, SO To Converth = h * 60.0
9 - IF H Is Negative, Add 360 To Complete The Conversion.
HSL 1 - IF S = 0, Define R, G, And B All to L (All IS DONE) 2 - OtherWise, Test L. IF L <0.5, TEMP2 = L * (1.0 S) IF L> = 0.5, TEMP2 = L S - L * S In The Colorbar Example for ColorBar Green, H = 120, L = 52, S = 79, SO Converting To the Range 0-1, L = .52, S = .79, SO TEMP2 = (. 52 .79) - (.52 * .79) = .899 3 - Compute TEMP1 = 2.0 * L - TEMP2 In The Example, Temp1 = 2.0 * .52 - .899 = .141 4 - Convert H to the Range 0-1 In The Example, H = 120/360 = .33 5 - for Each of R, G, B, Compute Another Temporary Value, Temp3, As Follows: For r, temp3 = h 1.0 / 3.0 For g, temp3 = h For B, Temp3 = H-1.0 / 3.0 IF TEMP3 <0, TEMP3 = TEMP3 1.0 IF Temp3> 1, TEMP3 = TEMP3 - 1.0 In the example, RTEMP3 = .33 .33 = .66, gtemp3 = .33, btemp3 = .33- .33 = 0 7 - for Each of R, G, B, DO The Following Test: IF 6.0 * Temp3 <1, color = Temp1 (TEMP2-TEMP1) * 6.0 * TEMP3 Else IF 2.0 * Temp3 <1, color = TEMP2 ELSE IF 3.0 * Temp3 <2, Color = Temp1 (Temp2-Temp1) * ((2.0 / 3.0) -Temp3) * 6.0 Else Color = Temp1 In The Example, 3.0 * RTEMP3 <2 SO r = .141 (((2.0 / 3.0-.66) * 6.0 = .141 2.0 * gtemp3 <1 so g = .899 6.0 * Btemp3 <1 so b = .141 (. 899-.141) * 6.0 * 0 = .1418 - Scale Back to the Range 0-100 to use the scaling shown in the video color Page For the example, r = 14, g = 90, b = 14 color in video
