Loading a Bitmap resource for OpenGL Texture[x]

I have been using this function to load Bitmaps for Textures in my OpenGL applications, taken from NeHe's tutorial:

Code:

---

AUX_RGBImageRec *LoadBMP(char *Filename) // Loads A Bitmap Image
{
FILE *File=NULL; // File Handle
if (!Filename) // Make Sure A Filename Was Given
{
return NULL; // If Not Return NULL
}
File=fopen(Filename,"r"); // Check To See If The File Exists
if (File) // Does The File Exist?
{
fclose(File); // Close The Handle
return auxDIBImageLoad(Filename); // Load The Bitmap And Return A Pointer
}
return NULL; // If Load Failed Return NULL
}

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I'm now dealing with a resource bitmap though, and I need something to replace Texture[0] = LoadBMP("bitmap.bmp").


I tried TextureImage[0] = auxDIBImageLoad(MAKEINTRESOURCE(IDB_BITMAP1), which compiles but the App crashes,

and TextureImage[0] = LoadImage(hInstance,MAKEINTRESOURCE(IDB_BITMAP1),I MAGE_BITMAP,0,0,LR_LOADFROMFILE);, where the compiler gives me a conversion error.

What could I use as a replacement?

Many people seen to be using this code to work with resources:

Code:

---

void LoadGLTextures()
{
// load bitmap from resource file
HBITMAP bitmap = LoadBitmap(GetModuleHandle(NULL),
MAKEINTRESOURCE(IDB_BITMAP2));

// setup 24 bits bitmap structure
// works on 8 bits bitmaps also!

BITMAPINFO info;
BITMAPINFOHEADER header;
header.biSize = sizeof(BITMAPINFOHEADER);
header.biWidth = 256;
header.biHeight = 256;
header.biPlanes = 1;
header.biBitCount = 24;
header.biCompression = BI_RGB;
header.biSizeImage = 0;
header.biClrUsed = 0;
header.biClrImportant = 0;
info.bmiHeader = header;
info.bmiColors->rgbRed = NULL;
info.bmiColors->rgbGreen = NULL;
info.bmiColors->rgbBlue = NULL;
info.bmiColors->rgbReserved = NULL;

// store bitmap data in a vector
const int size = 256*256*3;
unsigned char data[size];
HDC hdc = GetDC(g_hWndRender);
GetDIBits(hdc, bitmap, 0, 256, &data, &info, DIB_RGB_COLORS);
ReleaseDC(g_hWndRender, hdc);

// convert from BGR to RGB
unsigned char buff;
for(int i=0; i<256*256; i++)
{
buff = data[i*3];
if(i>=3)
{
data[i*3] = data[i*3+2];
data[i*3+2] = buff;
}
}

// create one texture
glGenTextures(1, &m_texture[0]);

// select texture
glBindTexture(GL_TEXTURE_2D, m_texture[0]);

// SetTextureParameters

// generate texture
glTexImage2D(GL_TEXTURE_2D, 0, 3, 256, 256, 0, GL_RGB, GL_UNSIGNED_BYTE, &data);
}

---

But I'm still new to programming, and I'm having trouble figuring out how that will help me assigning the .bmp to TextureImage[], as in the non-resource code:

Code:

---

AUX_RGBImageRec *TextureImage[1]; // Create Storage Space For The Texture
...
TextureImage[0] = LoadBMP("bitmap.bmp)

---

Here´s the pertinent code I'm using on my App. It´s now running, but no texture is being displayed.

Code:

---

int LoadGLTextures() // Load Bitmaps And Convert To Textures
{
 // load bitmap from resource file
 HBITMAP bitmap = LoadBitmap(GetModuleHandle(NULL), MAKEINTRESOURCE(IDB_BITMAP1));
 
 // setup 24 bits bitmap structure
 // works on 8 bits bitmaps also!
 BITMAPINFO info;
 BITMAPINFOHEADER header;
 header.biSize = sizeof(BITMAPINFOHEADER);
 header.biWidth = 256;
 header.biHeight = 128;
 header.biPlanes = 1;
 header.biBitCount = 24;
 header.biCompression = BI_RGB;
 header.biSizeImage = 0;
 header.biClrUsed = 0;
 header.biClrImportant = 0;
 info.bmiHeader = header;
 info.bmiColors->rgbRed = NULL;
 info.bmiColors->rgbGreen = NULL;
 info.bmiColors->rgbBlue = NULL;
 info.bmiColors->rgbReserved = NULL;
 // store bitmap data in a vector
 const int size = 256*256*3;
 unsigned char data[size];
 GetDIBits(hDC, bitmap, 0, 256, &data, &info, DIB_RGB_COLORS);
 ReleaseDC(hWnd,hDC);
 // convert from BGR to RGB
 unsigned char buff;
 for(int i=0; i<256*256; i++)
 {
  buff = data[i*3];
  if(i>=3)
  {
  data[i*3] = data[i*3+2];
  data[i*3+2] = buff;
  }
 }
 
  glGenTextures(1, &texture[0]); // Create The Texture
  // Build Texture
  {
  // Typical Texture Generation Using Data From The Bitmap
  glBindTexture(GL_TEXTURE_2D, texture[0]);
  // Generate The Texture
  glTexImage2D(GL_TEXTURE_2D, 0, 3, 256, 128, 0, GL_RGB, GL_UNSIGNED_BYTE, &data);
  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_LINEAR); // Linear Filtering
  glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR_MIPMAP_LINEAR); // Linear Filtering
  }
 }
 return true;
}

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i dont remember if you need to set the 'glTexEnvi' mode or not? im fairly certain you do.

but you need to set yor texture parameters and enviroments before you call 'glTexImage2D'. otherwise they're going to be applied to next texture instead of the one you want them for.

Code:

---


glBindTexture(GL_TEXTURE_2D, texture[0]);

glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_LINEAR); // Linear Filtering
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR_MIPMAP_LINEAR); // Linear Filtering


glTexEnvi(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_MODULATE); 

glTexImage2D(GL_TEXTURE_2D, 0, 3, 256, 128, 0, GL_RGB, GL_UNSIGNED_BYTE, &data);

---

note the "GL_MO DULATE" should be with no spaces... same with "GL_TEXTURE_MIN_FILTE R"

Thanks no-one :)

You should DeleteObject(hBitmap) at the end of your function to avoid a memory leak.

There is another method to do this that involves using a dibsection rather than GetDIBits. You can read an outline here.

If you can use the GL_BGR_EXT format with glTexImage2D you can skip converting the bitmap from BGR to RGB.