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carleton

OpenGL Correct way to draw an image

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I am having a strange problem. I am developing the application with Qt, so I am using their container, but I am drawing the image with standard OpenGL function, glDrawPixels. Depending on the size of the window, sometimes there is a horizontal line through the image. At first I though it might be my logic in generating the image, but when I changed the background color, the line changed colors, too. I am guessing that I am not setting up the glDrawPixels() correct which is why it skips a line sometimes. Initially I thought the problem might be that I was rounding thing off to integers, but I have rectified that so that everything uses floats, but the problem persists. Here is what I am doing: // Setting the zoom factor glPixelZoom( zoomFactor, zoomFactor); // Set the coord of where to start drawing the image on the screen glRasterPos2f( screenViewRect.x(), screenViewRect.y()); // ??Tell OpenGL how wide the view port is on the screen?? glPixelStoref(GL_UNPACK_SKIP_PIXELS, imgViewRect.x()); // ??Tell OpenGL how tall the view port is on the screen?? glPixelStoref(GL_UNPACK_SKIP_ROWS, imgViewRect.y()); // ??Set the scan line length of the original image?? glPixelStorei(GL_UNPACK_ROW_LENGTH, pDisplayImage->width()); // Draw the image glDrawPixels(imgViewRect.width(), imgViewRect.height(), GL_RGB, GL_UNSIGNED_BYTE, pDisplayImage->GetImagePtrConst()); Is my understanding of the process to drawing the image correct? Carleton

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