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// Check that the image’s width is a power of 2
if ( (surface->w & (surface->w – 1)) != 0 ) {
printf(“warning: image.bmp’s width is not a power of 2\n“);
}

// Also check if the height is a power of 2
if ( (surface->h & (surface->h – 1)) != 0 ) {
printf(“warning: image.bmp’s height is not a power of 2\n“);
}

//get number of channels in the SDL surface
nofcolors=surface->format->BytesPerPixel;

//contains an alpha channel
if(nofcolors==4)
{
if(surface->format->Rmask==0x000000ff)
texture_format=GL_RGBA;
else
texture_format=GL_BGRA;
}
else if(nofcolors==3) //no alpha channel
{
if(surface->format->Rmask==0x000000ff)
texture_format=GL_RGB;
else
texture_format=GL_BGR;
}
else
{
printf(“warning: the image is not truecolor…this will break “);
}

// Have OpenGL generate a texture object handle for us
glGenTextures( 1, &texture );

// Bind the texture object
glBindTexture( GL_TEXTURE_2D, texture );

// Set the texture’s stretching properties
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

glTexImage2D( GL_TEXTURE_2D, 0, nofcolors, surface->w, surface->h, 0,
texture_format, GL_UNSIGNED_BYTE, surface->pixels );
}
else {
printf(“SDL could not load image.bmp: %s\n“, SDL_GetError());
SDL_Quit();
return 1;
}

// Bind the texture to which subsequent calls refer to
glBindTexture( GL_TEXTURE_2D, texture );

glBegin( GL_QUADS );
// Top-left vertex (corner)
glTexCoord2i( 0, 0 );
glVertex3f( 100, 100, 0 );

// Bottom-left vertex (corner)
glTexCoord2i( 1, 0 );
glVertex3f( 228, 100, 0 );

// Bottom-right vertex (corner)
glTexCoord2i( 1, 1 );
glVertex3f( 228, 228, 0 );

SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );

glEnable( GL_TEXTURE_2D ); // Need this to display a texture

glViewport( 0, 0, 640, 480 );

glMatrixMode( GL_PROJECTION );
glLoadIdentity();

glOrtho( 0, 640, 480, 0, -1, 1 );

while( quit == false )
{
if( SDL_PollEvent( &event ) )
{
//If a key was pressed
if( event.type == SDL_KEYDOWN )
{
//Adjust the velocity
switch( event.key.keysym.sym )
{
case SDLK_ESCAPE:
quit=true;
break;
}
}

}
}

GLuint texture=NULL; //this is a handle to our texture object
GLenum texture_format=NULL;
GLint nofcolors;

SDL_Event event;

int loadImage()
{
SDL_Surface *surface; // this surface will tell us the details of the image

if ( (surface = IMG_Load(“flower.png”)) ) {

// Check that the image’s width is a power of 2
if ( (surface->w & (surface->w – 1)) != 0 ) {
printf(“warning: image.bmp’s width is not a power of 2\n“);
}

// Also check if the height is a power of 2
if ( (surface->h & (surface->h – 1)) != 0 ) {
printf(“warning: image.bmp’s height is not a power of 2\n“);
}

//get number of channels in the SDL surface
nofcolors=surface->format->BytesPerPixel;

//contains an alpha channel
if(nofcolors==4)
{
if(surface->format->Rmask==0x000000ff)
texture_format=GL_RGBA;
else
texture_format=GL_BGRA;
}
else if(nofcolors==3) //no alpha channel
{
if(surface->format->Rmask==0x000000ff)
texture_format=GL_RGB;
else
texture_format=GL_BGR;
}
else
{
printf(“warning: the image is not truecolor…this will break “);
}

// Have OpenGL generate a texture object handle for us
glGenTextures( 1, &texture );

// Bind the texture object
glBindTexture( GL_TEXTURE_2D, texture );

// Set the texture’s stretching properties
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

glTexImage2D( GL_TEXTURE_2D, 0, nofcolors, surface->w, surface->h, 0,
texture_format, GL_UNSIGNED_BYTE, surface->pixels );
}
else {
printf(“SDL could not load image.bmp: %s\n“, SDL_GetError());
SDL_Quit();
return 1;
}

// Free the SDL_Surface only if it was successfully created
if ( surface ) {
SDL_FreeSurface( surface );
}
}

void drawImage()
{

// Clear the screen before drawing
glClear( GL_COLOR_BUFFER_BIT );

// Bind the texture to which subsequent calls refer to
glBindTexture( GL_TEXTURE_2D, texture );

glBegin( GL_QUADS );
// Top-left vertex (corner)
glTexCoord2i( 0, 0 );
glVertex3f( 100, 100, 0 );

// Bottom-left vertex (corner)
glTexCoord2i( 1, 0 );
glVertex3f( 228, 100, 0 );

// Bottom-right vertex (corner)
glTexCoord2i( 1, 1 );
glVertex3f( 228, 228, 0 );

// Top-right vertex (corner)
glTexCoord2i( 0, 1 );
glVertex3f( 100, 228, 0 );
glEnd();
glLoadIdentity();
SDL_GL_SwapBuffers();
}

int init()
{
SDL_Surface *screen;

// Slightly different SDL initialization
if ( SDL_Init(SDL_INIT_VIDEO) != 0 ) {
printf(“Unable to initialize SDL: %s\n“, SDL_GetError());
return 1;
}

SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );

screen = SDL_SetVideoMode( 640, 480, 16, SDL_OPENGL);
if ( !screen ) {
printf(“Unable to set video mode: %s\n“, SDL_GetError());
return 1;
}
}

void init_GL()
{
// Set the OpenGL state after creating the context with SDL_SetVideoMode

glClearColor( 0, 0, 0, 0 );

glEnable( GL_TEXTURE_2D ); // Need this to display a texture

glViewport( 0, 0, 640, 480 );

glMatrixMode( GL_PROJECTION );
glLoadIdentity();

glOrtho( 0, 640, 480, 0, -1, 1 );

glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
}

void clean_up()
{
glDeleteTextures( 1, &texture );

SDL_Quit();
}

int main(int argc, char *argv[])
{
//Make sure the program waits for a quit
bool quit = false;

init();
init_GL();
loadImage();
drawImage();

while( quit == false )
{
if( SDL_PollEvent( &event ) )
{
//If a key was pressed
if( event.type == SDL_KEYDOWN )
{
//Adjust the velocity
switch( event.key.keysym.sym )
{
case SDLK_ESCAPE:
quit=true;
break;
}
}

}
}