Need several RGB convertion functions

kornerr · 09-20-2005, 10:18 AM

I'm using wxWidgets (and following OpenGL Game Development book).

VC++ has such functions (macros?) which are used in the book:

1) long RGB (GLubyte r, GLubyte g, GLubyte b);
2) GLubyte GetRValue (long rgb);
3) GLubyte GetGValue (long rgb);
4) GLubyte GetBValue (long rgb);

I need these functions in wxWidgets, but I don't have the slightest idea how to implement them.

Any ideas?

Thanks.

Thinking · 09-20-2005, 11:07 AM

i'm not sure if this works and i'm not the binary shift expert but try this:

typedef GLubyte char

#define GetRValue(rgb) rgb&0xFF0000
#define GetGValue(rgb) rgb&0x00FF00
#define GetBValue(rgb) rgb&0x0000FF

long RGB(char r,char g,char b){
long color=0;
color&=r;
color<<=8;
color&=g;
color<<=8;
color&=b;
return color;
}

if the above code works
i think a macro will also do it:
#define RGB(r,g,b) ((((r<<8)&g)<<8)&b)

addy86 · 09-20-2005, 12:26 PM

You forgot shifting (and always use parentheses with macros):

Code:

#define GetRValue(rgb) (((rgb)&0xFF0000)>>16)
#define GetGValue(rgb) (((rgb)&0x00FF00)>>8
#define GetBValue(rgb) ((rgb)&0x0000FF)

You have to use the or-operator:

Code:

long RGB(char r,char g,char b){
  return ( r << 16 ) | ( g << 8 ) | b;
}

The macro:

Code:

#define RGB(r,g,b) (((r)<<16)|((g)<<8)|(b))

Thinking · 09-20-2005, 12:42 PM

got it
your right
thx ;-)

kornerr · 09-21-2005, 05:07 AM

Thanks, Thinking, addy86.