Using the ChooseColor Common Dialog

[Kurt Kuzba]

This small PB/DLL program demonstrates the use of the ChooseColor common dialog.

I just used this as the basis for selecting colors in the halftone color converter
example program.
Nice. Thanks!

[Lance Edmonds]

Interesting, how to find RGB values for 256-colors palette ?

The default palette does not fill all 256 entries. Usually only about 20 are defined (I seem to recall the exact behavior is driver dependant), and the remaining entries are set by application(s) that alter the system palette.


------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Semen Matusovski]

This function finds "nearest" index for PB/CC COLOR
(initially was done in VB to find "clean" colors and was based on QBColor statement)

Function QbColorId (RGBComp As Dword) As Long
   Local RGBTest As Dword, ss As Quad, s As Quad
   Local i As Long, j As Long, ii As Long
   Local b1 As Byte Ptr, b2 As Byte Ptr
   For i = 0 To 15
      Select Case i
         Case  0: RgbTest = &H000000
         Case  1: RgbTest = &H800000
         Case  2: RgbTest = &H008000
         Case  3: RgbTest = &H808000
         Case  4: RgbTest = &H000080
         Case  5: RgbTest = &H800080
         Case  6: RgbTest = &H008080
         Case  7: RgbTest = &HC0C0C0
         Case  8: RgbTest = &H808080
         Case  9: RgbTest = &HFF0000
         Case 10: RgbTest = &H00FF00
         Case 11: RgbTest = &HFFFF00
         Case 12: RgbTest = &H0000FF
         Case 13: RgbTest = &HFF00FF
         Case 14: RgbTest = &H00FFFF
         Case 15: RgbTest = &HFFFFFF
      End Select
      b1 = VarPtr(RGBTest): b2 = VarPtr(RGBComp): s = 0
      For j = 1 To 3
         s = s + (@b1 - @b2) * (@b1 - @b2)
         Incr b1: Incr b2
      Next
      If (i = 0) Or (ss > s) Then ss = s: ii = i
   Next
   Function = ii
End Function

Usage for Eric's sample:
MsgBox Str$(QbColorId(ColorSpec.rgbResult)),,"PbCC Color"

Interesting, how to find RGB values for 256-colors pallette ?

------------------

In vb16 bit;

CC_Flags = CC_RGBINIT Or CC_PREVENTFULLOPEN



------------------

[Eric Pearson]

Hmmm... Not off the top of my head. The ChooseColor dialog is designed to allow the selection of any valid Windows color, so you probably couldn't restrict the display to 16 colors. So several of the standard color choices won't make sense in the context of a console app.

Or are you asking how you could write a "best match" function that could convert a TrueColor RGB value into the closest valid console color? I've never tried it, but it doesn't sound like it would be too difficult. Has anybody out there written one?

One interesting side note for PB/CC programmers... If your program will be run only on NT or 2000, it is possible to specify "custom colors" for each of the 16 standard COLOR values by editing the registry. But the settings will only take effect the next time your program is run, since Windows only reads the registry when it creates the console. But it can be a useful technique for giving your PB/CC apps a custom look.

-- Eric


------------------
Perfect Sync: Perfect Sync Development Tools
Email: mailto:[email protected][email protected]</A>

Eric,
Great routine. I'm trying to use it with PB/CC which has, as you are aware, only 16 colours.

Any tips on restricing the RGB function to the basic 16

TIA

------------------
Nigel Thomas

[Eric Pearson]

This small PB/DLL program demonstrates the use of the ChooseColor common dialog. If you change the two MSGBOX lines to PRINT and add a WAITKEY$ at the end, the program can also be compiled with PB/CC.

$DIM ALL
$REGISTER NONE
$COMPILE EXE
 
$INCLUDE "WIN32API.INC"
$INCLUDE "COMDLG32.INC"
 
FUNCTION PBMain AS LONG
 
    DIM ColorSpec AS LOCAL CHOOSECOLORAPI
    DIM lResult   AS LOCAL LONG
    DIM lCounter  AS LOCAL LONG
 
    DIM lCustomColor(15) AS LOCAL LONG 'array
 
    ColorSpec.lStructSize  = LEN(ColorSpec)
    ColorSpec.hwndOwner    = 0     'Handle of owner window.  If 0, dialog appears at top/left.
    ColorSpec.lpCustColors = VARPTR(lCustomColor(0))
    ColorSpec.rgbResult    = 255   'set the default color to Red (255,0,0)...
 
    'try these options one by one, for different effects...
    'ColorSpec.Flags = ColorSpec.Flags OR %CC_RGBINIT  'tells control to start at default color
    'ColorSpec.Flags = ColorSpec.Flags OR %CC_FULLOPEN
    'ColorSpec.Flags = ColorSpec.Flags OR %CC_PREVENTFULLOPEN
  
    'create a nice selection of colors for the custom colors (OPTIONAL)...
    RANDOMIZE TIMER
    FOR lCounter = 0 TO 15
        lCustomColor(lCounter) = RND(0,16777215)  'or RGB(lCounter*16,0,(15-lCounter)*16)
    NEXT
    '(You could also load custom colors from a file, or hard-code them.)
 
    lResult = ChooseColor(ColorSpec)
 
    IF lResult = 0 THEN
        MSGBOX "You chose the Cancel button.",,"Color Selection Demo"
    ELSE
        MSGBOX "You chose color value &h"+HEX$(ColorSpec.rgbResult,6),,"Color Selection Demo"
    END IF
 
    'You can also check then values in the lCustomColor() array to see if they've been changed.
 
    FUNCTION = 1
 
END FUNCTION

-------------
Perfect Sync: Perfect Sync Development Tools
Email: mailto:[email protected][email protected]</A>



[This message has been edited by Eric Pearson (edited March 01, 2000).]