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Thread: glDrawPixels and Color Control

  1. #1
    Junior Member Newbie
    Join Date
    Mar 2005

    glDrawPixels and Color Control

    I use glDrawPixels to draw an array of pixels.

    Image[i][j][1]=value; /green
    Image[i][j][2]=value; /blue
    Image[i][j][3]=value; / red


    I want blue pixels and white pixels. The blue ones shall have values of 8bit (0..255). But I am confused. When I set green "plane" to 255 and/or red "plane" to 255, I get strange colors. When I put red and green plane to 0, I get blue pixels (different brightness as I want) on BLACK pixels. But I want them on WHITE pixels.

    How does CONTROLLED RGB mixing with glDrawPixels work?? IŽd appreciate your help!!

  2. #2
    Super Moderator OpenGL Guru imported_dorbie's Avatar
    Join Date
    Jul 2000
    Bay Area, CA, USA

    Re: glDrawPixels and Color Control

    The format needs to match your array interleaving. With GL_RGB 0 = red, 1 = green, 2 = blue. With GL_BGR it's the other way around.

    With the C language arrays are numbered from 0, perhaps you're using fortran but it's worth mentioning. Even assuming fortran your array indexing is bogus. If it's C than this would only compile with an array of minor dimension 4 which means [3] would be alpha (with an RGBA or BGRA format).

    I wish you'd get more specific in future, you don't show your array declaration and you don't even bother to fill out your drawpixels arguments.

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