glColor4f(1.0f,1.0f,1.0f,alpha); // full Brightness, Alpha

glBlendFunc(GL_SRC_ALPHA,GL_ONE); // Blending Function for  translucency based on source alpha value>
 

glEnable(GL_BLEND);                      // Turn Blending on

glDisable(GL_DEPTH_TEST);        //Turn Depth Testing off
 

#include "SDL.h"
#include "SDL_image.h"
#include "SDL_opengl.h"

#include <stdio.h>

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

SDL_Event event;

float alpha=1.0f;
bool UP=false;         //Up key is pressed/released
bool DOWN=false;       //DOWN key is pressed/released</em>

<em>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-&gt;w &amp; (surface-&gt;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-&gt;h &amp; (surface-&gt;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-&gt;format-&gt;BytesPerPixel;

//contains an alpha channel
if(nofcolors==4)
{
if(surface-&gt;format-&gt;Rmask==0×000000ff)
texture_format=GL_RGBA;
else
texture_format=GL_BGRA;
}
else if(nofcolors==3) //no alpha channel
{
if(surface-&gt;format-&gt;Rmask==0×000000ff)
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, &amp;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-&gt;w, surface-&gt;h, 0,
texture_format, GL_UNSIGNED_BYTE, surface-&gt;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()
{
glClear( GL_COLOR_BUFFER_BIT );   // Clear the screen before drawing

glTranslatef(300.0,200.0,0.0);

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

glColor4f(1.0f,1.0f,1.0f,alpha);            // Full Brightness, Alpha
glBlendFunc(GL_SRC_ALPHA,GL_ONE);           // // Blending Function For Translucency Based On Source Alpha Value

glBegin( GL_QUADS );
// Top-left vertex (corner)
glTexCoord2i( 0, 0 );
glVertex3f( -64, -64, 0 );

// Bottom-left vertex (corner)
glTexCoord2i( 1, 0 );
glVertex3f( 64, -64, 0 );

// Bottom-right vertex (corner)
glTexCoord2i( 1, 1 );
glVertex3f( 64, 64, 0 );

// Top-right vertex (corner)
glTexCoord2i( 0, 1 );
glVertex3f( -64, 64, 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
glEnable(GL_BLEND);                  // Turn Blending On
glDisable(GL_DEPTH_TEST);         //Turn Depth Testing Off</em>

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, &amp;texture );</em>

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( &amp;event ) )
{
//If a key was pressed
if( event.type == SDL_KEYDOWN )
{
//Adjust the velocity
switch( event.key.keysym.sym )
{
case SDLK_UP:
UP=true;
break;
case SDLK_DOWN:
DOWN=true;
break;
case SDLK_ESCAPE:
quit=true;
break;
}
}
//If a key was released
else if( event.type == SDL_KEYUP )
{
//Adjust the velocity
switch( event.key.keysym.sym )
{
case SDLK_UP:
UP=false;
break;
case SDLK_DOWN:
DOWN=false;
break;
}
}
}

// If UP key is pressed

if(UP==true){
if(alpha&lt;1.0f)         // make sure alpha value is not greater than maximum value 1.0
alpha+=0.01f;       //increase the alpha value, fade out
drawImage();
}

else if(DOWN==true){    //If DOWN key is pressed
if(alpha&gt;0.0f)       // make sure value of alpha is not less than 0.0f
alpha-=0.01f;      // decrease the alpha value, fade in
drawImage();
}

}

clean_up();
return 0;
}