luminance

[Kentman]

I can get a colour of a cell using Mycell.Interior.ColorIndex in a function but can I get the luminance?

 

[shg]

Public Declare Function ColorRGBToHLS Lib "shlwapi.dll" ( _
                                      ByVal clrRGB As Long, _
                                      pwHue As Long, _
                                      pwLum As Long, _
                                      pwSat As Long) As Long
Sub demo()
    MsgBox GetLuminance(Selection.Cells(1).Interior.Color)
End Sub
 
Function GetLuminance(iColor As Long) As Long
    Dim iHue        As Long
    Dim iSat        As Long
    Dim iLum        As Long
 
    ColorRGBToHLS iColor, iHue, iLum, iSat
    GetLuminance = iLum
End Function

Returns values in the range 0 to 240.

 

[hiker95]

Kentman,


See:

Aaron Blood
The Luminance Formula:
R * 0.3 + G * 0.59 + B * 0.11 = L
http://www.ozgrid.com/forum/showthread.php?t=141215&page=1


http://spreadsheetpage.com/index.php/comments/exploring_theme_colors/


http://www.mvps.org/dmcritchie/excel/colors.htm
Color Luminance (#Luma)
In color television luminance is calculated (approximately) like this (1 = white, represented by 1V signal voltage):
L = R*0.3+G*0.59+B*0.11
This formula was created to make the color video signal compatible with black and white monitors/receivers. Monochrome monitors are still in use as professional viewfinders on many TV cameras, since they create a sharper image than one made from a color matrix. Posted by Harald Staff, plus the reference below.
Poynton ’s Color FAQ, Charles Poynton [alt] [archive] -- see item #9.