source: network-game/graphics_library/common/texture.cpp@ f15d6a9

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <GL/glew.h>

#include <GLFW/glfw3.h>


GLuint loadBMP_custom(const char * imagepath){

        printf("Reading image %s\n", imagepath);

        // Data read from the header of the BMP file
        unsigned char header[54];
        unsigned int dataPos;
        unsigned int imageSize;
        unsigned int width, height;
        // Actual RGB data
        unsigned char * data;

        // Open the file
        FILE * file = fopen(imagepath,"rb");
        if (!file)                                                          {printf("%s could not be opened. Are you in the right directory ? Don't forget to read the FAQ !\n", imagepath); getchar(); return 0;}

        // Read the header, i.e. the 54 first bytes

        // If less than 54 bytes are read, problem
        if ( fread(header, 1, 54, file)!=54 ){ 
                printf("Not a correct BMP file\n");
                return 0;
        }
        // A BMP files always begins with "BM"
        if ( header[0]!='B' || header[1]!='M' ){
                printf("Not a correct BMP file\n");
                return 0;
        }
        // Make sure this is a 24bpp file
        if ( *(int*)&(header[0x1E])!=0  )         {printf("Not a correct BMP file\n");    return 0;}
        if ( *(int*)&(header[0x1C])!=24 )         {printf("Not a correct BMP file\n");    return 0;}

        // Read the information about the image
        dataPos    = *(int*)&(header[0x0A]);
        imageSize  = *(int*)&(header[0x22]);
        width      = *(int*)&(header[0x12]);
        height     = *(int*)&(header[0x16]);

        // Some BMP files are misformatted, guess missing information
        if (imageSize==0)    imageSize=width*height*3; // 3 : one byte for each Red, Green and Blue component
        if (dataPos==0)      dataPos=54; // The BMP header is done that way

        // Create a buffer
        data = new unsigned char [imageSize];

        // Read the actual data from the file into the buffer
        fread(data,1,imageSize,file);

        // Everything is in memory now, the file wan be closed
        fclose (file);

        // Create one OpenGL texture
        GLuint textureID;
        glGenTextures(1, &textureID);
        
        // "Bind" the newly created texture : all future texture functions will modify this texture
        glBindTexture(GL_TEXTURE_2D, textureID);

        // Give the image to OpenGL
        glTexImage2D(GL_TEXTURE_2D, 0,GL_RGB, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data);

        // OpenGL has now copied the data. Free our own version
        delete [] data;

        // Poor filtering, or ...
        //glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
        //glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); 

        // ... nice trilinear filtering.
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); 
        glGenerateMipmap(GL_TEXTURE_2D);

        // Return the ID of the texture we just created
        return textureID;
}

// Since GLFW 3, glfwLoadTexture2D() has been removed. You have to use another texture loading library, 
// or do it yourself (just like loadBMP_custom and loadDDS)
//GLuint loadTGA_glfw(const char * imagepath){
//
//      // Create one OpenGL texture
//      GLuint textureID;
//      glGenTextures(1, &textureID);
//
//      // "Bind" the newly created texture : all future texture functions will modify this texture
//      glBindTexture(GL_TEXTURE_2D, textureID);
//
//      // Read the file, call glTexImage2D with the right parameters
//      glfwLoadTexture2D(imagepath, 0);
//
//      // Nice trilinear filtering.
//      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
//      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
//      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
//      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); 
//      glGenerateMipmap(GL_TEXTURE_2D);
//
//      // Return the ID of the texture we just created
//      return textureID;
//}



#define FOURCC_DXT1 0x31545844 // Equivalent to "DXT1" in ASCII
#define FOURCC_DXT3 0x33545844 // Equivalent to "DXT3" in ASCII
#define FOURCC_DXT5 0x35545844 // Equivalent to "DXT5" in ASCII

GLuint loadDDS(const char * imagepath){

        unsigned char header[124];

        FILE *fp; 
 
        /* try to open the file */ 
        fp = fopen(imagepath, "rb"); 
        if (fp == NULL){
                printf("%s could not be opened. Are you in the right directory ? Don't forget to read the FAQ !\n", imagepath); getchar(); 
                return 0;
        }
   
        /* verify the type of file */ 
        char filecode[4]; 
        fread(filecode, 1, 4, fp); 
        if (strncmp(filecode, "DDS ", 4) != 0) { 
                fclose(fp); 
                return 0; 
        }
        
        /* get the surface desc */ 
        fread(&header, 124, 1, fp); 

        unsigned int height      = *(unsigned int*)&(header[8 ]);
        unsigned int width           = *(unsigned int*)&(header[12]);
        unsigned int linearSize  = *(unsigned int*)&(header[16]);
        unsigned int mipMapCount = *(unsigned int*)&(header[24]);
        unsigned int fourCC      = *(unsigned int*)&(header[80]);

 
        unsigned char * buffer;
        unsigned int bufsize;
        /* how big is it going to be including all mipmaps? */ 
        bufsize = mipMapCount > 1 ? linearSize * 2 : linearSize; 
        buffer = (unsigned char*)malloc(bufsize * sizeof(unsigned char)); 
        fread(buffer, 1, bufsize, fp); 
        /* close the file pointer */ 
        fclose(fp);

        unsigned int components  = (fourCC == FOURCC_DXT1) ? 3 : 4; 
        unsigned int format;
        switch(fourCC) 
        { 
        case FOURCC_DXT1: 
                format = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT; 
                break; 
        case FOURCC_DXT3: 
                format = GL_COMPRESSED_RGBA_S3TC_DXT3_EXT; 
                break; 
        case FOURCC_DXT5: 
                format = GL_COMPRESSED_RGBA_S3TC_DXT5_EXT; 
                break; 
        default: 
                free(buffer); 
                return 0; 
        }

        // Create one OpenGL texture
        GLuint textureID;
        glGenTextures(1, &textureID);

        // "Bind" the newly created texture : all future texture functions will modify this texture
        glBindTexture(GL_TEXTURE_2D, textureID);
        glPixelStorei(GL_UNPACK_ALIGNMENT,1);   
        
        unsigned int blockSize = (format == GL_COMPRESSED_RGBA_S3TC_DXT1_EXT) ? 8 : 16; 
        unsigned int offset = 0;

        /* load the mipmaps */ 
        for (unsigned int level = 0; level < mipMapCount && (width || height); ++level) 
        { 
                unsigned int size = ((width+3)/4)*((height+3)/4)*blockSize; 
                glCompressedTexImage2D(GL_TEXTURE_2D, level, format, width, height,  
                        0, size, buffer + offset); 
         
                offset += size; 
                width  /= 2; 
                height /= 2; 

                // Deal with Non-Power-Of-Two textures. This code is not included in the webpage to reduce clutter.
                if(width < 1) width = 1;
                if(height < 1) height = 1;

        } 

        free(buffer); 

        return textureID;


}