bmp texture not loading correctly using Open GL - c++

Question

Hello everyone I'm trying to load a texture (normal map) using OpenGL.
GLuint loadTexture(const char* fileName) {
GLuint textureID;
glGenTextures(1, &textureID);
// load file - using core SDL library
SDL_Surface* tmpSurface;
tmpSurface = SDL_LoadBMP(fileName);
if (tmpSurface == nullptr) {
std::cout << "Error loading bitmap" << std::endl;
}
// bind texture and set parameters
glBindTexture(GL_TEXTURE_2D, textureID);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, tmpSurface->w, tmpSurface->h, 0,
GL_BGR, GL_UNSIGNED_BYTE, tmpSurface->pixels);
glGenerateMipmap(GL_TEXTURE_2D);
SDL_FreeSurface(tmpSurface);
return textureID;
}
then if I try to render it, it gives me that :
Instead of :
But I can render this normaly :
Do you have an idea ? color deep is 32 for the one that is not working and 24 for the working one

Answer 1

Use SDL_ConvertSurfaceFormat to convert the surface format and load the converted curface:
SDL_Surface* tmpSurface = SDL_LoadBMP(fileName);
SDL_Surface* formattedSurface = SDL_ConvertSurfaceFormat(
tmpSurface, SDL_PIXELFORMAT_ABGR8888, 0);
SDL_FreeSurface(tmpSurface);
// [...]
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, tmpSurface->w, tmpSurface->h, 0,
GL_RGBA, GL_UNSIGNED_BYTE, formattedSurface->pixels);
SDL_FreeSurface(formattedSurface);
Of course you can evaluate the format attribute of the SDL_Surface and set a proper format attribute when two-dimensional texture image is specified by glTexImage2D.