/*
 *  readBMP.c
 *
 *  Created by Nina Amenta on Sun May 23 2004.
 *  Free to good home!
 *
 */

#include <stdio.h>      // Header file for standard file i/o.
#include <stdlib.h>     // Header file for malloc/free.
#include "readBMP.h"

/* Simple BMP reading code, should be adaptable to many
systems. Originally from Windows, ported to Linux, now works on my Mac
OS system.

NOTE!! only reads 24-bit RGB, single plane, uncompressed, unencoded
BMP, not all BMPs. BMPs saved by xv should be fine. */

//
// This code was created by Jeff Molofee '99 
//  (www.demonews.com/hosted/nehe)
// Ported to Linux/GLUT by Richard Campbell '99
// Code and comments for adaptation to big endian/little endian systems 
// Nina Amenta '04
//

/* Reads a long 32 bit integer; comment out one or the other shifting line below, 
whichever makes your system work right. */
unsigned int endianReadInt(FILE* file) {
unsigned char  b[4]; 
unsigned int i;

   if ( fread( b, 1, 4, file) < 4 )
     return 0;
   /* LITTLE VS BIG ENDIAN LINES - comment out one or the other */
   i = (b[3]<<24) | (b[2]<<16) | (b[1]<<8) | b[0]; // big endian
   //i = (b[0]<<24) | (b[1]<<16) | (b[2]<<8) | b[3]; // little endian
   return i;
}

/* Reads a 16 bit integer; comment out one or the other shifting line below, 
whichever makes your system work right. */
unsigned short int endianReadShort(FILE* file) {
unsigned char  b[2]; 
unsigned short s;

   if ( fread( b, 1, 2, file) < 2 )
     return 0;
   /* LITTLE VS BIG ENDIAN LINES - comment out one or the other */
   s = (b[1]<<8) | b[0]; // big endian
   //s = (b[0]<<8) | b[1]; // little endian
   return s;
}


// quick and dirty bitmap loader...for 24 bit bitmaps with 1 plane only.  
// See http://www.dcs.ed.ac.uk/~mxr/gfx/2d/BMP.txt for more info.
int ImageLoad(char *filename, Image *image) {
    FILE *file;
    unsigned long size;                 // size of the image in bytes.
    unsigned long i;                    // standard counter.
    unsigned short int planes;          // number of planes in image (must be 1) 
    unsigned short int bpp;             // number of bits per pixel (must be 24)
    char temp;                          // temporary color storage for bgr-rgb conversion.

    // make sure the file is there.
    if ((file = fopen(filename, "rb"))==NULL)
    {
	printf("File Not Found : %s\n",filename);
	return 0;
    }
    
    // seek through the bmp header, up to the width/height:
    fseek(file, 18, SEEK_CUR);

    // read the width
    if (!(image->sizeX = endianReadInt(file))) {
	printf("Error reading width from %s.\n", filename);
	return 0;
    }
    printf("Width of %s: %lu\n", filename, image->sizeX);
    
    // read the height 
    if (!(image->sizeY = endianReadInt(file))) {
	printf("Error reading height from %s.\n", filename);
	return 0;
    }
    printf("Height of %s: %lu\n", filename, image->sizeY);
    
    // calculate the size (assuming 24 bits or 3 bytes per pixel).
    size = image->sizeX * image->sizeY * 3;

    // read the planes
    if (!(planes=endianReadShort(file))) {
	printf("Error reading planes from %s.\n", filename);
	return 0;
    }
    if (planes != 1) {
	printf("Planes from %s is not 1: %u\n", filename, planes);
	return 0;
    }

    // read the bits per pixel
    if (!(bpp = endianReadShort(file))) {
	printf("Error reading bpp from %s.\n", filename);
	return 0;
    }
    if (bpp != 24) {
	printf("Bpp from %s is not 24: %u\n", filename, bpp);
	return 0;
    }
	
    // seek past the rest of the bitmap header.
    fseek(file, 24, SEEK_CUR);

    // read the data. 
    image->data = (char *) malloc(size);
    if (image->data == NULL) {
	printf("Error allocating memory for color-corrected image data");
	return 0;	
    }

    if ((i = fread(image->data, size, 1, file)) != 1) {
	printf("Error reading image data from %s.\n", filename);
	return 0;
    }

    for (i=0;i<size;i+=3) { // reverse all of the colors. (bgr -> rgb)
	temp = image->data[i];
	image->data[i] = image->data[i+2];
	image->data[i+2] = temp;
    }
    
    // we're done.
    return 1;
}