Reverse RGB() ?

[volfreak]

I have a grid and want the users to be able to set the dynamic fore and back color. I can get the color dialog box (GETCOLOR()) but it returns a single numeric value while the dynamic requires the character string in RGB format.

I know I can take the RGB() and convert the 3 individual values to the single numeric (for fore color and back color - why one set of properties is numeric and the other RGB character is beyond me). However, I cannot figure out how to take the single numeric value provided by GETCOLOR() and have it converted to the 3 values in RGB format.

Anyone have any ideas on how to do this? And why there is only one conversion direction RGB->##? The 'why' is not as important as the 'how'.

Thanks much in advance for any and all help.

 

[Eguy]

Hi volfreak

The result of RGB() is a number between 0 and 16,777,215 (which is 256^3 minus one).

The formula used to compute the result is
nBlueValue * (256^2) + nGreenValue * 256 + nRedValue

HTH
Ed
Please let me know if the sugestion(s) I provide are helpful to you.
Sometimes you're the windshield... Sometimes you're the bug.

 

[ChrisRChamberlain]

volfreak

LOCAL r, g, b

red = 0
green = 0
blue = 0

getRGB(getColor(),@red,@green,@blue)

? red
? green
? blue

FUNC getRGB(colour,red,green,blue)
PRIVATE p,i

p = (256 ^ 2)
i = INT(colour / p)
blue = i
colour = colour - (i * p)
p = (256 ^ 1)
i = INT(colour / p)
green = i
colour = colour - (i * p)
red = INT(colour)

HTH

Chris

 

[chpicker]

Actually, the DynamicBack/ForeColor properties don't need to be in RGB() format. You can specify the single number and it will work just fine.

Here is the program I wrote that does this. I use this to convert the results of the API call GetSysColor to values I can understand.
[tt]
lparameters nInColor,nRed,nGreen,nBlue,lOutput
* Parameters 2-4 should be passed BY REFERENCE
LOCAL nColor
nColor=nInColor
nBlue=INT(nColor/65536)
nColor=nColor%65536
nGreen=INT(nColor/256)
nRed=nColor%256
IF type("lOutput&quot='L' and lOutput
?"RED: "
??nRed
?"GREEN: "
??nGreen
?"BLUE: "
??nBlue
ENDIF
RETURN
[/tt]
To call the function, you need to initialize 3 variables to pass to it. The 3 variables can be individual variables, 3 elements of an array, or 3 properties of an object. The optional 5th parameter, if .T., will output the colors to the screen. Here are examples:
[tt]
STORE 0 TO lnRed,lnGreen,lnBlue
FromRGB(8723642,@lnRed,@lnGreen,@lnBlue,.T.)

DIMENSION aColors[3]
FromRGB(8723642,@aColors[1],@aColors[2],@aColors[3])

oCol=CreateObject("RGBClass&quot
FromRGB(8723642,@oCol.red,@oCol.Green,@oCol.Blue)

DEFINE CLASS RGBClass AS Custom
red=0
green=0
blue=0
ENDDEFINE
[/tt]
Hope that helps,

Ian

 

[volfreak]

Thanks for all of the suggestions. I figured there was a mathematical calculation for the conversion and was hoping someone else had already done that. Thanks much!!!!

Thanks also for the code snippets. When looking at the on-line help it shows cColor (or something similar) for the dynamicfore/backcolor properties. I didn't see a reference to a numeric value. That's good to know that the method will accept the numeric color value.

Cheers,

 

[chpicker]

The reason it's listed as cColor (the c indicating that it's a CHARACTER expression) is because the value for DynamicBackColor has to be a string. This string gets evaluated every time the control refreshes, but it must ultimately resolve into a single numeric number representing a color.

The RGB() function generates that number. If you already have that number, though, it would be kinda pointless to run a function to break it into RGB values just to feed it back into the RGB() function.

Good luck!

Ian

 

[volfreak]

In the words or the famous Homer, "DOH!" Yes, Simpson not of the Iliad & Odyssey fame. ;-)

Ding Ding that makes sense. Thanks for 'setting me straight'. ;-)

 

[chpicker]

Glad I could help )

Ian