textureLoader.cpp

/**
	* File:    textureLoader.cpp
	*
	* Author1:  Akshay Tiwari (2018A7PS0201H)
	* Author2:  Mushkan Surekha  (2018B5A70477H)
	* Author3:  Mahesh Swaminathan  (2018A4PS0982H)
	* Date:     09-04-2020
	* Course:   Computer Graphics (IS F311)
	*
	* Summary of File:
	*
	*   Program to load texture given in a .DDS file using a 
	*	simple parser and then generate a texture ID for
	*	this texture.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <glad.h>
#include "textureLoader.hpp"
#include <GLFW/glfw3.h>

/**
	*   GLuint loadBMP(const char* imagepath)
	*
	*   Summary of loadBMP function:
	*
	*       Loads a .bmp texture.
	*
	*   Parameters  :
	*	
	*		File path of the texture
	*
	*   Return Value : 
	*
	*		Texture ID of the read texture
	*
	*   Description :
	*
	*       Loads a .bmp texture.
*/
GLuint loadBMP(const char* imagepath) {

	printf("Reading image %s\n", imagepath);
	unsigned char header[54];
	unsigned int dataPos;
	unsigned int imageSize;
	unsigned int width, height;

	unsigned char* data;

	FILE* file = fopen(imagepath, "rb");
	if (!file) {
		printf("%s could not be opened.\n", imagepath);
		getchar();
		return 0;
	}
	if (fread(header, 1, 54, file) != 54) {
		printf("Not a correct BMP file\n");
		fclose(file);
		return 0;
	}
	if (header[0] != 'B' || header[1] != 'M') {
		printf("Not a correct BMP file\n");
		fclose(file);
		return 0;
	}
	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; }
	dataPos = *(int*)&(header[0x0A]);
	imageSize = *(int*)&(header[0x22]);
	width = *(int*)&(header[0x12]);
	height = *(int*)&(header[0x16]);

	if (imageSize == 0)    imageSize = width * height * 3; 
	if (dataPos == 0)      dataPos = 54; 

	data = new unsigned char[imageSize];
	fread(data, 1, imageSize, file);
	fclose(file);

	GLuint textureID;
	glGenTextures(1, &textureID);
	glBindTexture(GL_TEXTURE_2D, textureID);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data);
	delete[] data;

	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 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)
	*
	*   Summary of loadDDS function:
	*
	*       Loads a .DDS texture.
	*
	*   Parameters  :
	*
	*		File path of the texture
	*
	*   Return Value :
	*
	*		Texture ID of the read texture
	*
	*   Description :
	*
	*       Loads a .DDS texture.
*/
GLuint loadDDS(const char* imagepath) {

	unsigned char header[124];
	FILE* fp;
	fp = fopen(imagepath, "rb");
	if (fp == NULL) {
		printf("%s could not be opened.\n", imagepath); getchar();
		return 0;
	}

	char filecode[4];
	fread(filecode, 1, 4, fp);
	if (strncmp(filecode, "DDS ", 4) != 0) {
		fclose(fp);
		return 0;
	}

	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;
	bufsize = mipMapCount > 1 ? linearSize * 2 : linearSize;
	buffer = (unsigned char*)malloc(bufsize * sizeof(unsigned char));
	fread(buffer, 1, bufsize, fp);
	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;
	}

	GLuint textureID;
	glGenTextures(1, &textureID);
	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;
		if (width < 1) width = 1;
		if (height < 1) height = 1;
	}
	free(buffer);
	return textureID;
}