Reversing a COlour Code

[Tim Marshall]

I use Terry Kreft's & Stephen Lebans colour dialog procedures for users
to pick colours for various control properties in certain apps.

Is there a way to take the colour code that is displayed in a
backcolor/forecolor/etc property and calculate the "reverse colour"? In
other words, If a user picks 255 (red) for a control backcolor, I'd like
to be able to calculate the opposite or negative of that colour and
assign the control's forecolor property the new colour.

vbWhite and other colour constants are not an option, I don't think,
since the colour dialog allows a user to blend their own custom colour...

TIA for any help.
--
Tim http://www.ucs.mun.ca/~tmarshal/
^o<
/#) "Burp-beep, burp-beep, burp-beep?" - Quaker Jake
/^^ "What's UP, Dittoooooo?" - Ditto

[Allen Browne]

Parse the color into bytes for red, green, and blue, using integer division
and Mod.
Flip the bits by NOTing them
Combine them with the RGB() function.

Assuming the RGB value is in a text box named txtCombined:
Dim btRed As Byte, btGreen As Byte, btBlue As Byte
Dim lngColor as Long
btRed = Me.txtCombined Mod 256
lngColor = Me.txtCombined \ 256
btGreen = lngColor Mod 256
btBlue = lngColor \ 256

btRed = Not btRed
'etc.

--
Allen Browne - Microsoft MVP. Perth, Western Australia.
Tips for Access users - http://allenbrowne.com/tips.html
Reply to group, rather than allenbrowne at mvps dot org.

"Tim Marshall" <TI****@PurpleP andaChasers.Moe rtherium> wrote in message
news:do******** **@coranto.ucs. mun.ca...

I use Terry Kreft's & Stephen Lebans colour dialog procedures for users to
pick colours for various control properties in certain apps.

Is there a way to take the colour code that is displayed in a
backcolor/forecolor/etc property and calculate the "reverse colour"? In
other words, If a user picks 255 (red) for a control backcolor, I'd like
to be able to calculate the opposite or negative of that colour and assign
the control's forecolor property the new colour.

vbWhite and other colour constants are not an option, I don't think, since
the colour dialog allows a user to blend their own custom colour...

TIA for any help.
--
Tim http://www.ucs.mun.ca/~tmarshal/
^o<
/#) "Burp-beep, burp-beep, burp-beep?" - Quaker Jake
/^^ "What's UP, Dittoooooo?" - Ditto

[Lyle Fairfield]

Very early in the morning and without coffee my sense of logic says:

Not ColorCode And vbWhite
should reverse any RGB type color.

---

or

Not ColorCode And 16777215 if the constant vbWhite isn't available?

---

[Not ColorCode] should reverse all the bits.
[And vbWhite] should return the bits in the fourth byte to zero.

[Tim Marshall]

Allen Browne wrote:

Parse the color into bytes for red, green, and blue, using integer division
and Mod.

HI Allen - thanks to you and Lyle for your responses. For posterity,
here's the function I based on your submission (Lyle's seemed to work,
but for the very limited amount of testing I did with it, I kept getting
black colours).

I tried parsing the colour into integers since the RGB() function
requires integer arguments, but I ended up with vastly different looking
colours which were mostly black. I don't understand why using bytes
worked better, but <shrug>
Public Function fReverseColour( lngColour As Long) As Long

'Takes an RGB colour spec and reverses it.
'Thanks to Allen Browne & Lyle Fairfield's responses on cdma
'
'Argument LngColour is the colour code fed from a colour
'property of a control's BackColor (the usual one used
'in TCM), foreColor, etc.

Dim bytRed As Byte, bytGreen As Byte, bytBlue As Byte

Dim bytTemp As Byte

'Before using the above bytRed, etc bytes,
'use bytTemp for a calculation because for some
'lngColour codes such as the standard Access default
'form BG colour, the results of some of the division and
'mod functions is greater than 255. See error handling

Dim lngC As Long

On Error GoTo Err_Proc

bytTemp = lngColour Mod 256

bytRed = bytTemp

lngC = lngColour \ 256

bytTemp = lngC Mod 256

bytGreen = bytTemp

bytTemp = lngC \ 256

bytBlue = bytTemp

bytRed = Not bytRed

bytGreen = Not bytGreen

bytBlue = Not bytBlue

fReverseColour = RGB(bytRed, bytGreen, bytBlue)

Debug.Print "Original Colour Fed: " & lngColour & _
" Reverse: " & fReverseColour

Exit_Proc:

Exit Function

Err_Proc:

Select Case Err.Number

Case 6 'overflow on bytTemp calc

bytTemp = 255

Resume Next

Case Else

MsgBox "Error " & Err.Number & " " & _
Err.Description , vbCritical, _
"Function fReverseColour" , Err.HelpFile _
, Err.HelpContext

Resume Exit_Proc

End Select

End Function

--
Tim http://www.ucs.mun.ca/~tmarshal/
^o<
/#) "Burp-beep, burp-beep, burp-beep?" - Quaker Jake
/^^ "What's UP, Dittoooooo?" - Ditto

[Randy Harris]

"Tim Marshall" <TI****@PurpleP andaChasers.Moe rtherium> wrote in message
news:do******** **@coranto.ucs. mun.ca...

Allen Browne wrote:

Parse the color into bytes for red, green, and blue, using integer division and Mod.

HI Allen - thanks to you and Lyle for your responses. For posterity,
here's the function I based on your submission (Lyle's seemed to work,
but for the very limited amount of testing I did with it, I kept getting
black colours).

I tried parsing the colour into integers since the RGB() function
requires integer arguments, but I ended up with vastly different looking
colours which were mostly black. I don't understand why using bytes
worked better, but <shrug>
Public Function fReverseColour( lngColour As Long) As Long

'Takes an RGB colour spec and reverses it.
'Thanks to Allen Browne & Lyle Fairfield's responses on cdma
'
'Argument LngColour is the colour code fed from a colour
'property of a control's BackColor (the usual one used
'in TCM), foreColor, etc.

Dim bytRed As Byte, bytGreen As Byte, bytBlue As Byte

Dim bytTemp As Byte

'Before using the above bytRed, etc bytes,
'use bytTemp for a calculation because for some
'lngColour codes such as the standard Access default
'form BG colour, the results of some of the division and
'mod functions is greater than 255. See error handling

Dim lngC As Long

On Error GoTo Err_Proc

bytTemp = lngColour Mod 256

bytRed = bytTemp

lngC = lngColour \ 256

bytTemp = lngC Mod 256

bytGreen = bytTemp

bytTemp = lngC \ 256

bytBlue = bytTemp

bytRed = Not bytRed

bytGreen = Not bytGreen

bytBlue = Not bytBlue

fReverseColour = RGB(bytRed, bytGreen, bytBlue)

Debug.Print "Original Colour Fed: " & lngColour & _
" Reverse: " & fReverseColour

Exit_Proc:

Exit Function

Err_Proc:

Select Case Err.Number

Case 6 'overflow on bytTemp calc

bytTemp = 255

Resume Next

Case Else

MsgBox "Error " & Err.Number & " " & _
Err.Description , vbCritical, _
"Function fReverseColour" , Err.HelpFile _
, Err.HelpContext

Resume Exit_Proc

End Select

End Function

--
Tim http://www.ucs.mun.ca/~tmarshal/
^o<
/#) "Burp-beep, burp-beep, burp-beep?" - Quaker Jake
/^^ "What's UP, Dittoooooo?" - Ditto

Tim, I think this will work to compute "complement ary" colors:

NewColor = &HFFFFFF Xor OldColor

?vbred
255
?vbgreen
65280
?vbblue
16711680
?&HFFFFFF xor vbred
16776960
?vbgreen + vbblue
16776960
?&HFFFFFF xor vbblue
65535
?vbgreen + vbred
65535
?&HFFFFFF xor (vbblue + vbgreen)
255

--
Randy Harris
tech at promail dot com
I'm pretty sure I know everything that I can remember.

[Lyle Fairfield]

Tim

Have you thought about SystemColors? Many default colors in Access are
System Colors. (They are the long negative numbers.) Unlike RGB colors
they use the fourth byte and reversing them by manipulating only the
RGB bytes generally returns black.

I offer this for anyone (you included of course) who wants to work with
System Colors as well as RGB Colors.

Const MinimumSystemCo lor As Long = &H80000001
Const MaximumSystemCo lor As Long = &H80000018

Private Declare Function OleTranslateCol or Lib "oleaut32" _
(ByVal SystemColorCons tants As Long, _
ByVal Pallette As Long, _
RGBColor As Long) As Long

Public Function ReverseColor(By Val Color As Long) As Long
If Color >= MinimumSystemCo lor And Color <= MaximumSystemCo lor Then
OleTranslateCol or Color, 0, Color
End If
ReverseColor = Not Color And vbWhite
End Function

[Tim Marshall]

Lyle Fairfield wrote:

Tim

Have you thought about SystemColors? Many default colors in Access are
System Colors. (They are the long negative numbers.) Unlike RGB colors
they use the fourth byte and reversing them by manipulating only the
RGB bytes generally returns black.
THanks. Hmmmmmm. Actually, to be honest, my function tends to usually
return black. For the most part, the lngColour argument fed into it are
custom colours made by the user previously using the colour picker (The
Kreft/Lebans utility I mentioned in my original post). So they are not
usually negative (thanks very much for that explanation, BTW, I've
always wondered why a few colours were negative - the fourth byte might
actually why my function had to have an error handler for error 6,
overflow - I think).

I must ask a couple of questions:
I offer this for anyone (you included of course) who wants to work with
System Colors as well as RGB Colors.

Const MinimumSystemCo lor As Long = &H80000001
Const MaximumSystemCo lor As Long = &H80000018
The values you've used here for min/max system colours - what do they
mean? This looks a bit like the sort of colouring coding I've done in
my rather basic html work.

How do you know &H80000001 and &H80000018 are the min/max system
colours? Is this a windows property?
Private Declare Function OleTranslateCol or Lib "oleaut32" _
(ByVal SystemColorCons tants As Long, _
ByVal Pallette As Long, _
RGBColor As Long) As Long

Public Function ReverseColor(By Val Color As Long) As Long
If Color >= MinimumSystemCo lor And Color <= MaximumSystemCo lor Then
OleTranslateCol or Color, 0, Color
End If
ReverseColor = Not Color And vbWhite
End Function

I appreciate your responses on this, thanks.
--
Tim http://www.ucs.mun.ca/~tmarshal/
^o<
/#) "Burp-beep, burp-beep, burp-beep?" - Quaker Jake
/^^ "What's UP, Dittoooooo?" - Ditto

[Tim Marshall]

Tim Marshall wrote:

THanks. Hmmmmmm. Actually, to be honest, my function tends to usually
return black.

YOu may, in this case, call me a stupid backwoods newfie (and I won't go
ballistic like I usually do when I hear our equivalent of the "n"
word)... the reason things were returning black was simply because the
code I had which called my fReverseColour function applied the resultant
colour to the backcolor instead of the forecolor property... With
backstyle being transparant, I was seeinbg no effect of my function
whatsoever, though it had seemed to work well in the debug window as far
as different colours go.

&*^^&*% What a moron.
--
Tim http://www.ucs.mun.ca/~tmarshal/
^o<
/#) "Burp-beep, burp-beep, burp-beep?" - Quaker Jake
/^^ "What's UP, Dittoooooo?" - Ditto

[Lyle Fairfield]

I haven't found a great pgae that describes min and max system colors.
To get my min and max values I just looked at the Object Browser. I
missed &H80000000 so my range should be adjusted:
Const MinimumSystemCo lor As Long = &H80000000

[Lyle Fairfield]

We all figure out all the tough parts and then doing something not so
clever with the result quite regularly.