VBA function to convert RGB values into OpenCV HSV values.
Note: These bits of code are mostly for my own reference, but if anyone else finds them useful all the better.
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Function RGB_to_HSV(R As Integer, G As Integer, B As Integer, ChannelToReturn As Integer) As Integer Dim ReturnValue As Integer Dim H, S, V As Integer Dim TempH, TempS, TempV As Double Dim TempR, TempG, TempB As Double Dim MinRGBInteger, MaxRGBInteger As Integer Dim MinRGBDouble, MaxRGBDouble As Double TempR = R / 255 TempG = G / 255 TempB = B / 255 MinRGBInteger = Application.WorksheetFunction.Min(R, G, B) MaxRGBInteger = Application.WorksheetFunction.Max(R, G, B) MinRGBDouble = MinRGBInteger / 255 MaxRGBDouble = MaxRGBInteger / 255 V = MaxRGBInteger TempV = V / 255 If (V <> 0) Then TempS = (TempV - MinRGBDouble) / TempV Else TempS = 0 End If If (MinRGBInteger <> MaxRGBInteger) Then If (V = R) Then TempH = ((60 * (TempG - TempB)) / (TempV - MinRGBDouble)) End If If (V = G) Then TempH = 120 + (60 * (TempB - TempR) / (TempV - MinRGBDouble)) End If If (V = B) Then TempH = 240 + (60 * (TempR - TempG) / (TempV - MinRGBDouble)) End If If (TempH < 0) Then TempH = TempH + 360 End If Else TempH = 0 End If H = TempH / 2 S = 255 * TempS Select Case ChannelToReturn Case 1 ReturnValue = H Case 2 ReturnValue = S Case 3 ReturnValue = V End Select RGB_to_HSV = ReturnValue End Function |
Thanks! Note that the two additional functions could be avoided.
Instead of
GetRGBMinimum(r,g,b)useApplication.WorksheetFunction.Min(r,g,b).Instead of
GetRGBMaximum(r,g,b)useApplication.WorksheetFunction.Max(r,g,b)Thanks!
Thanks. I hope you don’t mind if I point out a coding techniques for you.
It may help you and others. VB has a variable declaration shortfall which catches very many people unawares.
You can’t correctly declare multiple variables on a line as you have done.
e.g. Dim TempH, TempS, TempV As Double
Only the first variable will be declared as a ‘double’. the other ones in the row get declared as type ‘variant’. Try using the debugger and step through the code with Watches on the variables. You will see that only TempV is set as type ‘double’.
TempH & TempS will be variant. I know, it’s just one of VB’s quirks.
You have to explicitly declare each type i.e.
Dim TempH As Double, TempS As Double, TempV As Double