Thread: 24bit pixel plotting

  1. #1
    Registered User
    Join Date
    Feb 2003

    24bit pixel plotting

    Im reading the book "Tricks of the Windows Game Programming Gurus." I just now read over plotting pixels in 16bit, 24bit, 32bit colors. I know how to do them now but I dont exactly understand how 24 bit is working(although I do know how...but I hate not understanding how its doing it). Heres the code the book shows...

    inline void Plot_Pixel_24(int x, int y, 
                              int red, int green, int blue, 
                              UCHAR *video_buffer, int lpitch)
    // this function plots a pixel in 24-bit color mode
    // assuming that the caller already locked the surface
    // and is sending a pointer and byte pitch to it
    // in byte or 8-bit math the proper address is: 3*x + y*lpitch
    // this is the address of the low order byte which is the Blue channel
    // since the data is in RGB order
    DWORD pixel_addr = (x+x+x) + y*lpitch;
    // write the data, first blue
    video_buffer[pixel_addr]   = blue;
    // now red
    video_buffer[pixel_addr+1] = green;
    // finally green
    video_buffer[pixel_addr+2] = red;
    } // end Plot_Pixel_24
    When it plots the three different colors is it just ploting them very close to each other to where it mixes the colors or what? I was also wandering why [pixel_addr] has to be blue, [pixel_addr+1] has to be green, [pixel_addr+2] has to be red.

    video_buffer is a pointer to surface and lpitch is a pointer to the direct draw surface description lpitch.

  2. #2
    Has a Masters in B.S.
    Join Date
    Aug 2001
    because 24 bit color takes three bytes, each byte holds a color, they are almost always ordered (R)ed,(G)reen,(B)lue, or RGB.
    ADVISORY: This users posts are rated CP-MA, for Mature Audiences only.

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