Texture.cpp

#include <stdio.h>
#include <windows.h>
// #include <gl\glaux.h>		// Header File For The Glaux Library
#include "glut.h"
#include <Texture.h>

/**********************************************************
 *
 * VARIABLES DECLARATION
 *
 *********************************************************/

int num_texture = -1; // Counter to keep track of the last loaded texture

/**********************************************************
 *
 * FUNCTION LoadBitmap(char *)
 *
 * This function loads a bitmap file and return the OpenGL reference ID to use that texture
 *
 *********************************************************/

int LoadTexture(char *filename, int alpha)
{
    int i, j = 0;             // Index variables
    FILE *l_file;             // File pointer
    unsigned char *l_texture; // The pointer to the memory zone in which we will load the texture

    // windows.h gives us these types to work with the Bitmap files
    BITMAPFILEHEADER fileheader;
    BITMAPINFOHEADER infoheader;
    RGBTRIPLE rgb;

    num_texture++; // The counter of the current texture is increased

    if ((l_file = fopen(filename, "rb")) == NULL)
        return (-1); // Open the file for reading

    fread(&fileheader, sizeof(fileheader), 1, l_file); // Read the fileheader

    fseek(l_file, sizeof(fileheader), SEEK_SET);       // Jump the fileheader
    fread(&infoheader, sizeof(infoheader), 1, l_file); // and read the infoheader

    // Now we need to allocate the memory for our image (width * height * color deep)
    l_texture = (byte *)malloc(infoheader.biWidth * infoheader.biHeight * 4);
    // And fill it with zeros
    memset(l_texture, 0, infoheader.biWidth * infoheader.biHeight * 4);

    // At this point we can read every pixel of the image
    for (i = 0; i < infoheader.biWidth * infoheader.biHeight; i++)
    {
        // We load an RGB value from the file
        fread(&rgb, sizeof(rgb), 1, l_file);

        // And store it
        l_texture[j + 0] = rgb.rgbtRed;   // Red component
        l_texture[j + 1] = rgb.rgbtGreen; // Green component
        l_texture[j + 2] = rgb.rgbtBlue;  // Blue component
        l_texture[j + 3] = alpha;         // Alpha value
        j += 4;                           // Go to the next position
    }

    fclose(l_file); // Closes the file stream

    glBindTexture(GL_TEXTURE_2D, num_texture); // Bind the ID texture specified by the 2nd parameter

    // The next commands sets the texture parameters
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); // If the u,v coordinates overflow the range 0,1 the image is repeated
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); // The magnification function ("linear" produces better results)
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); // The minifying function

    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECR);

    // Finally we define the 2d texture
    glTexImage2D(GL_TEXTURE_2D, 0, 4, infoheader.biWidth, infoheader.biHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, l_texture);

    // And create 2d mipmaps for the minifying function
    gluBuild2DMipmaps(GL_TEXTURE_2D, 4, infoheader.biWidth, infoheader.biHeight, GL_RGBA, GL_UNSIGNED_BYTE, l_texture);

    free(l_texture); // Free the memory we used to load the texture

    return (num_texture); // Returns the current texture OpenGL ID
}