> If this don't is enough, tellme please; by exaple, maybe you require real
> time image processing.

> #include <windows.h>
> #include <math.h>

> BYTE GetIntensity(COLORREF color) {
>   BYTE r;
>   BYTE g;
>   BYTE b;
>   BYTE i;
> /** each COLORREF (or simply color) is a vector of three components  (red,
> green and blue).*/

>   r=  getRValue(color); /**retrieve red component*/
>   g= getGValue(color); /**and green component */
>   b= getBValue(color); /** also blue */

>   i= sqrt( r*r +g*g +b*b )/sqrt(3.0);  /**compare this operation with to
> obtain vectorial norm.*/
>   return (BYTE)i;
> }

> An exanple to use is:
>   COLORREF color= GetPixel(dc,x,y); /** someone Device Context, someone
> position inside */
>   BYTE gray= GetIntensity(color);
>   SetPixel(dc,gray,gray,gray);
> And, how you must think; the color pixel in x,y position is rempalced by
> another in gray scale.

> Regards.

> Tigrux.
> ICQ #45507615
> sflo...@fcfm.uanl.mx

> [snip]
> >  i= sqrt( r*r +g*g +b*b )/sqrt(3.0);  /**compare this operation with to
> >obtain vectorial norm.*/
> [snip]

> Hi,

>     you have to use one of the follwing two formulas in order
> to pay attention for CRT phosphors and human eyes when
> converting to grayscale:

> Y = 0.114 * Blue + 0.587 * Green + 0.299 * Red

> or

> Y = 0.072169 * Blue  + 0.715160 * Green + 0.21267 * Red

> (second preferred)

> where Y is the luminance level.

> Then you have to rebuild TColor in this manner:

> TColor( (int)Y * (65536 + 256 + 1) );

> Hope this helps.

> Ciao!

> Giuliano

> [snip]
> >TColor? Is this from something like OWL or VCL? I don't have BCB, I've
got
> >free command line tools (BCC 5.5), so I can't use this stuff. How would
that
> >look in plain Win32 API.
> [snip]

> Ok, I've intended that you working with VCL: Ignore TColor.
> For Win32 API you could try to search on SDK's
> Win32 Programmer's Reference online-help for
> RGBQUAD and RGBTRIPLE (I think) .

> Ciao!

> Giuliano

> > These are structures. One of 4 and second of 3 members. How can they be
> > connected with TColor((int)Y* (65536+256+1)); ? This TColor thingy seems
to
> > get int, but RGBQUAD and RGBTRIPLE seem to have R, G, B, and one
reserved
> > (for RGBQUAD). I need red, green and blue values to use them and not
only Y.

> You compute the Y and stuff it into the R, G and B elements.  Grayscale
values
> are defined by RGB(i, i, i), where i = 0 .. 255.  So even though you have
16,777,216
> colors with 24-bit graphics, you only have 256 shades of gray.

> --
> efg

> Earl F. Glynn     E-mail:  EarlGl...@att.net
> Overland Park, KS  USA

> efg's Computer Lab:  http://www.efg2.com/Lab