/***************************************************************************
 * File: frame.c                                                           *
 *                                                                         *
 * Desc: This program performs frame operations between 2 images           *
 ***************************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <alloc.h>
#include <math.h>
#include "ip.h"

#define frame_operation(X1, X2)        (((unsigned int) (X1) + (X2))/2) 

extern int getnum(FILE *fp);

int main(int argc, char *argv[])
    {
    char file1[100];                    /* name of first input file */
    char file2[100];                    /* name of second input file */
    char fileout[100];                  /* name of output file */
    int rows, cols;                     /* image rows and columns */
    unsigned long i,j;                  /* x and y loop variables */
    unsigned long bytes_per_pixel;      /* number of bytes per image pixel */
    unsigned char *buff1, *buff2;       /* input line buffers */
    unsigned char *buff_out;            /* output line buffer */
    int file_type;                      /* what type of image data */
    FILE *fp1, *fp2;                    /* input file pointers */
    FILE *fpout;                        /* output file pointer */
    int firstchar, secchar;             /* first and second characters of file */
    int line;                           /* size of line in bytes */
    int temp;                           /* temporary variable */

    /* set input filename and output file name */
    if(argc == 4)
	{
	strcpy(file1, argv[1]);
	strcpy(file2, argv[2]);
	strcpy(fileout, argv[3]);
	}
    else
	{
	printf("Input name of first input file\n");
	gets(file1);
	printf("Input name of second input file\n");
	gets(file2);
	printf("\nInput name of output file\n");
	gets(fileout);
	printf("\n");
	}

    if((fpout = fopen(fileout, "wb")) == NULL)
	{
	printf("Unable to open %s for writing\n",fileout);
	exit(1);
	}

    if((fp1 = fopen(file1, "rb")) == NULL)
	{
	printf("Unable to open %s for reading\n",file1);
	exit(1);
	}

    firstchar = getc(fp1);
    secchar = getc(fp1);

    if(firstchar != 'P')
	{
	printf("You silly goof... This is not a PPM file!\n");
	exit(1);
	}

    cols = getnum(fp1);
    rows = getnum(fp1);
    getnum(fp1);     /* consume max value from input file header */

    if((fp2 = fopen(file2, "rb")) == NULL)
	{
	printf("Unable to open %s for reading\n",file2);
	exit(1);
	}

    firstchar = getc(fp2);
    if(getc(fp2) != secchar)
	{
	printf("Input files are different types...exiting\n");
	exit(1);
	}

    if(firstchar != 'P')
	{
	printf("You silly goof... This is not a PPM file!\n");
	exit(1);
	}

    if(getnum(fp2) != cols)
	{
	printf("different column sizes...exiting\n");
	exit(1);
	}

    if(getnum(fp2) != rows)
	{
	printf("different row sizes...exiting\n");
	exit(1);
	}

    getnum(fp2);     /* consume max value from input file header */

    /* determine bytes_per_pixel, 3 for color, 1 for gray-scale */
    if(toupper(secchar)  == 'P')
	{
	bytes_per_pixel = 3;
	file_type = PPM;
	}
    else
	{
	bytes_per_pixel = 1;
	file_type = PGM;
	}

    line = bytes_per_pixel * cols;
    buff1 = malloc(line);
    buff2 = malloc(line);
    buff_out = malloc(line);

    if((buff1 == NULL) || (buff2 == NULL) || (buff_out == NULL))
	{
	printf("unable to malloc enough memory for measley frame process\n");
	exit(1);
	}

    /* print output file header */
    fprintf(fpout,"P%c\n%d %d\n255\n",secchar, cols, rows);
    /* operate on two images and write output one line at a time */
    for(i=0; i<rows; i++)
	{
	fread(buff1, 1, line, fp1);
	fread(buff2, 1, line, fp2);
	for(j=0; j<line; j++)
	    {
	    temp = frame_operation(buff1[j], buff2[j]);
	    CLIP(temp, 0, 255);
	    buff_out[j] = temp;
	    }
	fwrite(buff_out, 1, line, fpout);
	}

    free(buff1);
    free(buff2);
    free(buff_out);
    fclose(fp1);
    fclose(fp2);
    fclose(fpout);
    return 0;
    }