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    <p>After some experimentation, I think that I've found a solution that appears to be suitable for my own purposes. First, given the example code in my question above, it appears that the pixmap needs to be passed to the <code>glDrawPixels</code> function as an array <code>GLubyte color[2][2][4]</code> with an alpha channel. As mentioned by Vaayu, there is also a possibility that the <code>glMatrixMode</code> function needs to be set up correctly. Second, according to pg. 356 of the OpenGL Programming Guide (7th Edition), the current raster position needs to be set if the <code>glPixelZoom</code> function is called with negative arguments. Essentially why I couldn't see an image was due to the raster being drawn at a position not within the viewable area of the window. The following code demonstrates how to set the rotation and the current raster position for four separate cases:</p> <p><pre><code> // case 0 glWindowPos2i(0, 0); glPixelZoom(scaleX, scaleY);</p> <p>// case 1 glWindowPos2i(windowHeight, 0); glPixelZoom(-scaleX, scaleY);</p> <p>// case 2 glWindowPos2i(0, windowHeight); glPixelZoom(scaleX, -scaleY);</p> <p>// case 3 glWindowPos2i(windowWidth, windowHeight); glPixelZoom(-scaleX, -scaleY); </pre></code></p> <p>So the example given in my original question can be updated:</p> <pre> class Pixmap { public: GLubyte color[2][2][4]; Pixmap() { // red color[0][0][0] = 255; color[0][0][1] = 0; color[0][0][2] = 0; color[0][0][3] = 0; // green color[0][1][0] = 0; color[0][1][1] = 255; color[0][1][2] = 0; color[0][1][3] = 0; // blue color[1][0][0] = 0; color[1][0][1] = 0; color[1][0][2] = 255; color[1][0][3] = 0; // white color[1][1][0] = 255; color[1][1][1] = 255; color[1][1][2] = 255; color[1][1][3] = 0; } void render() { glClear(GL_COLOR_BUFFER_BIT); glDrawPixels( 2, 2, GL_RGBA, GL_UNSIGNED_BYTE, color ); glFlush(); } }; // Create an instance of class Pixmap Pixmap myPixmap; void myRender() { myPixmap.render(); } int main( int argc, char *argv[] ) { int screenWidth, screenHeight; int rotation; // Choose rotation case {0, 1, 2, 3} rotation = 3; glutInit(&argc, argv); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA); screenWidth = glutGet(GLUT_SCREEN_WIDTH); screenHeight = glutGet(GLUT_SCREEN_HEIGHT); int windowWidth = screenHeight / 2; int windowHeight = screenHeight / 2; glutInitWindowSize(windowWidth, windowHeight); int posX = (screenWidth - windowWidth) / 2; int posY = (screenHeight - windowHeight) / 4; glutInitWindowPosition(posX, posY); glutCreateWindow("Picture"); GLfloat scaleX = 1.0f * windowWidth / 2; GLfloat scaleY = 1.0f * windowHeight / 2; glMatrixMode(GL_MODELVIEW); // Select rotation switch(rotation) { case 0: glWindowPos2i(0, 0); glPixelZoom(scaleX, scaleY); break; case 1: glWindowPos2i(windowHeight, 0); glPixelZoom(-scaleX, scaleY); break; case 2: glWindowPos2i(0, windowHeight); glPixelZoom(scaleX, -scaleY); break; case 3: glWindowPos2i(windowWidth, windowHeight); glPixelZoom(-scaleX, -scaleY); break; default: break; } glClearColor(1.0, 1.0, 1.0, 0.0); glColor3f(0.0f, 0.0f, 0.0f); glutDisplayFunc( myRender ); glutMainLoop(); } </pre>
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