Issues with textures using OpenGL

[DeadEli]

I am currently using Dev C++ as my IDE. I am attempting to learn to add texture. I may be completely off here, but this is what I have. It creates a white box in the center of the screen(which should have my texture in). I found something showing how to add the texture, but it didn't explain how to first open the file. I think my issue may be with opening the image. Here is my code:

/**************************
 * Includes
 *
 **************************/

#include <windows.h>
#include <gl/gl.h>
#include <stdio.h>

/**************************
 * Function Declarations
 *
 **************************/

LRESULT CALLBACK WndProc (HWND hWnd, UINT message,
WPARAM wParam, LPARAM lParam);
void EnableOpenGL (HWND hWnd, HDC *hDC, HGLRC *hRC);
void DisableOpenGL (HWND hWnd, HDC hDC, HGLRC hRC);

/*FILE * pFile;
pFile = fopen ("myfile.txt","r");
if (pFile!=NULL)
{
          
fclose (pFile);
}*/

void DrawTexture()
     {
FILE * pFile;
pFile = fopen ("texture.png","r");
if (pFile!=NULL)
{

     glBindTexture(GL_TEXTURE_2D, 13);
     glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
     glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
     glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
     glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
     glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
     glTexImage2D (GL_TEXTURE_2D, 0, GL_RGB, 64, 64, 0, GL_RGB, GL_UNSIGNED_BYTE, pFile);
     
     glBindTexture (GL_TEXTURE_2D, 13);
     glBegin (GL_QUADS);
     glTexCoord2f (0.0, 0.0);
     glVertex3f (-1.0, -1.0, 0.0);
     glTexCoord2f (1.0, 0.0);
     glVertex3f (-1.0, 1.0, 0.0);
     glTexCoord2f (1.0, 1.0);
     glVertex3f (1.0, 1.0, 0.0);
     glTexCoord2f (0.0, 1.0);
     glVertex3f (1.0, -1.0, 0.0);
     glEnd ();

fclose (pFile);
}
}


/**************************
 * WinMain
 *
 **************************/

int WINAPI WinMain (HINSTANCE hInstance,
                    HINSTANCE hPrevInstance,
                    LPSTR lpCmdLine,
                    int iCmdShow)
{
    WNDCLASS wc;
    HWND hWnd;
    HDC hDC;
    HGLRC hRC;        
    MSG msg;
    BOOL bQuit = FALSE;
    float theta = 0.0f;

    /* register window class */
    wc.style = CS_OWNDC;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hInstance;
    wc.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor (NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH) GetStockObject (BLACK_BRUSH);
    wc.lpszMenuName = NULL;
    wc.lpszClassName = "GLSample";
    RegisterClass (&wc);

    /* create main window */
    hWnd = CreateWindow (
      "GLSample", "OpenGL Sample", 
      WS_CAPTION | WS_POPUPWINDOW | WS_VISIBLE,
      400, 100, 256, 256,
      NULL, NULL, hInstance, NULL);

    /* enable OpenGL for the window */
    EnableOpenGL (hWnd, &hDC, &hRC);

    /* program main loop */
    while (!bQuit)
    {
        /* check for messages */
        if (PeekMessage (&msg, NULL, 0, 0, PM_REMOVE))
        {
            /* handle or dispatch messages */
            if (msg.message == WM_QUIT)
            {
                bQuit = TRUE;
            }
            else
            {
                TranslateMessage (&msg);
                DispatchMessage (&msg);
            }
        }
        else
        {
            /* OpenGL animation code goes here */

            glClearColor (0.0f, 0.0f, 0.0f, 0.0f);
            glClear (GL_COLOR_BUFFER_BIT);

            glPushMatrix ();

            /*glBegin (GL_TRIANGLES);
            glColor3f (1.0f, 0.0f, 0.0f);   glVertex2f (0.0f, 1.0f);
            glColor3f (0.0f, 1.0f, 0.0f);   glVertex2f (0.87f, -0.5f);
            glColor3f (0.0f, 0.0f, 1.0f);   glVertex2f (-0.87f, -0.5f);
            glEnd ();*/
            DrawTexture();
            glPopMatrix ();
            SwapBuffers (hDC);   
        }
    }

    /* shutdown OpenGL */
    DisableOpenGL (hWnd, hDC, hRC);

    /* destroy the window explicitly */
    DestroyWindow (hWnd);

    return msg.wParam;
}


/********************
 * Window Procedure
 *
 ********************/

LRESULT CALLBACK WndProc (HWND hWnd, UINT message,
                          WPARAM wParam, LPARAM lParam)
{

    switch (message)
    {
    case WM_CREATE:
        return 0;
    case WM_CLOSE:
        PostQuitMessage (0);
        return 0;

    case WM_DESTROY:
        return 0;

    case WM_KEYDOWN:
        switch (wParam)
        {
        case VK_ESCAPE:
            PostQuitMessage(0);
            return 0;
        }
        return 0;

    default:
        return DefWindowProc (hWnd, message, wParam, lParam);
    }
}


/*******************
 * Enable OpenGL
 *
 *******************/

void EnableOpenGL (HWND hWnd, HDC *hDC, HGLRC *hRC)
{
    PIXELFORMATDESCRIPTOR pfd;
    int iFormat;

    /* get the device context (DC) */
    *hDC = GetDC (hWnd);

    /* set the pixel format for the DC */
    ZeroMemory (&pfd, sizeof (pfd));
    pfd.nSize = sizeof (pfd);
    pfd.nVersion = 1;
    pfd.dwFlags = PFD_DRAW_TO_WINDOW | 
      PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
    pfd.iPixelType = PFD_TYPE_RGBA;
    pfd.cColorBits = 24;
    pfd.cDepthBits = 16;
    pfd.iLayerType = PFD_MAIN_PLANE;
    iFormat = ChoosePixelFormat (*hDC, &pfd);
    SetPixelFormat (*hDC, iFormat, &pfd);

    /* create and enable the render context (RC) */
    *hRC = wglCreateContext( *hDC );
    wglMakeCurrent( *hDC, *hRC );

}


/******************
 * Disable OpenGL
 *
 ******************/

void DisableOpenGL (HWND hWnd, HDC hDC, HGLRC hRC)
{
    wglMakeCurrent (NULL, NULL);
    wglDeleteContext (hRC);
    ReleaseDC (hWnd, hDC);
}

I commented out a triangle, which can be drawn(just under the white square). I also separated the sections where I open the image. Any help would be great.

[Disch]

You have many problems:


1) You need to call glEnable() and enable 2D texturing. I believe the call is glEnable(GL_TEXTURE_2D), but double check that.

2) You can't just call glBindTexture and give it an arbitrary texture number (13? wtf?). You need to actually create a texture with glGenTextures.

3) You aren't loading pixel data properly either. OpenGL takes raw pixel data... ie: RGBA data. PNGs are compressed and store all sorts of other stuff in them. Even if you get this texture to display, the graphics will not be what you expect. You'll need to extract the pixel data from the png file somehow (typically another lib is used)

4) You're also opening the file in text mode, which will not work for binary data files like PNG.



I recommend using a support lib to help with this kind of thing. SFML, in particular, makes loading and displaying images very easy. It also simplifies window management/creation and makes it cross-platform. Check it out: http://www.sfml-dev.org