Question

I am relatively new to OpenGL and I am having some issues when I am rendering an image as a texture for a QUAD which is as the same size of the image. Here is my code. I would be very grateful if someone helps me to solve this problem. The image appears way smaller and is squished. (BTW, the image dimensions are 500×375).

glGenTextures( 1, &S_GLator_InputFrameTextureIDSu );
        glBindTexture(GL_TEXTURE_2D, S_GLator_InputFrameTextureIDSu);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
        glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);

        glTexImage2D( GL_TEXTURE_2D, 0, 4, S_GLator_EffectCommonData.mRenderBufferWidthSu, S_GLator_EffectCommonData.mRenderBufferHeightSu, 0, GL_RGBA, GL_UNSIGNED_BYTE, dataP);
glBindTexture(GL_TEXTURE_2D, S_GLator_InputFrameTextureIDSu);
        glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, S_GLator_EffectCommonData.mRenderBufferWidthSu, S_GLator_EffectCommonData.mRenderBufferHeightSu, GL_RGBA, GL_UNSIGNED_BYTE, bufferP);
//set the matrix modes
        glMatrixMode( GL_PROJECTION );
        glLoadIdentity();
        //gluPerspective( 45.0, (GLdouble)widthL / heightL, 0.1, 100.0 );
        glOrtho (0, 1, 0, 1, -1, 1);
        // Set up the frame-buffer object just like a window.
        glViewport( 0, 0, widthL, heightL );
        glDisable(GL_DEPTH_TEST);
        glClearColor( 0.0f, 0.0f, 0.0f, 0.0f );
        glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );


        glMatrixMode( GL_MODELVIEW );
        glLoadIdentity();


        glBindTexture( GL_TEXTURE_2D, S_GLator_InputFrameTextureIDSu );


        //Render the geometry to the frame-buffer object


        glBegin(GL_QUADS); //input frame
            glColor4f(1.f,1.f,1.f,1.f);
            glTexCoord2f(0.0f,0.0f);    
            glVertex3f(0.f ,0.f ,0.0f);
            glTexCoord2f(1.0f,0.0f);    
            glVertex3f(1.f ,0.f,0.0f);
            glTexCoord2f(1.0f,1.f); 
            glVertex3f(1.f ,1.f,0.0f);
            glTexCoord2f(0.0f,1.f); 
            glVertex3f(0.f ,1.f,0.0f);
        glEnd();

Answer 1

First, your image dimensions must be powers of two, not just arbitrary 500×375. Second, the internalformat (third) argument to glTexImage2D should be a symbolic constant, describing the internal format layout, not just "4", as it’s deprecated since OpenGL 1.2. Third, your dataP and bufferP storage layout must correspond to the current GL_UNPACK_ALIGNMENT. Fourth, your equilateral quad, on which you’re trying to put the texture on, is essentially square, and thus your non-square texture will appear squashed or stretched with such a texture coordinates.