color superposition

[Frank Kestens]

I'm writing a program in which I need to superimpose two or more colors.
Is this possible ? and with which instructions ?
For example : I draw a circle in red and nearby a circle in green . The intersected region should appear in red+green = yellow . Adding also blue should give white .
??

[Petr Schreiber jr]

Hi,

if you have latest PB/WIN or PB/CC, you can try to use GRAPHIC commands and %MIX_MERGESRC mode for rendering the image.

Here is minimal sample:

FUNCTION PBMAIN () AS LONG

  LOCAL hWin AS DWORD

  GRAPHIC WINDOW "Demo", -1, -1, 240, 240 TO hWin

  GRAPHIC ATTACH hWin, 0
  GRAPHIC CLEAR %BLACK
  GRAPHIC SET MIX %MIX_MERGESRC
  GRAPHIC ELLIPSE (10, 10) - (110, 110),%RED, %RED
  GRAPHIC ELLIPSE (30, 30) - (130, 130),%GREEN, %GREEN
  GRAPHIC ELLIPSE (60, 60) - (160, 160),%BLUE, %BLUE

  SLEEP 5000  ' show it for 5 seconds, then end

END FUNCTION

You could also use additive blending in OpenGL or Direct3D.

And the most straightforward way is to just extract Red, Green, Blue components of the two fragments, combine them to create new one ( just check to not go over 255 in each component ).

You can use GetRValue, GetGValue, GetBValue from Win32 API to get the components, or use other way.


Petr

[Frank Kestens]

color superposition

This works ! Thank you very much !
I've never heard before of the Merge function and wasn't aware of all the nice possibilities !
BTW : is the ThinBasic really written entirely in PBasic ?

[Eros Olmi]

BTW : is the ThinBasic really written entirely in PBasic ?

A bit late
Yes it is 95% written using PowerBasic for Windows.
The 5% remaining is in MS C.