texture.cpp

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

#include <glad.h>

#include <GLFW/glfw3.h>

#define _CRT_SECURE_NO_WARNINGS

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");
        fclose(file);
        return 0;
    }
    // A BMP files always begins with "BM"
    if ( header[0]!='B' || header[1]!='M' ){
        printf("Not a correct BMP file\n");
        fclose(file);
        return 0;
    }
    // Make sure this is a 24bpp file
    if ( *(int*)&(header[0x1E])!=0  )         {printf("Not a correct BMP file\n");    fclose(file); return 0;}
    if ( *(int*)&(header[0x1C])!=24 )         {printf("Not a correct BMP file\n");    fclose(file); 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 can 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);
    // ... which requires mipmaps. Generate them automatically.
    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;


}