/*	Author:		Jonathan Hardy
	File:		thresh.cc

	This file reads in a binary PGM file and thresholds out pixels
	below a minimum and above a maximum, then writes the news image
	out to a new PGM file.
*/

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

FILE *ptr;				// Image file
FILE *threshptr;			// Output file

void main(int argc, char**argv) 
{
char fname[13];				// Image filename
char threshname[18];			// Output filename
char width[4], height[4], numcol[4];	// Image information
char Type[3];				// Image type (P5)
int r, c, data;				// Counters and image data variable
char temp[100];				// Variable for input comment lines
char comment[17];			// Variable for output comment

strcpy(fname, argv[1]);			// Get filename from command line
strcat(fname, ".pgm");			// Append filename with ".pgm"
const int ulimit = atoi(argv[2]);	// Get upper threshold
const int llimit = atoi(argv[3]);	// Get lower threshold
ptr = fopen(fname, "rb");		// Open image file
fread(&Type, 3, 1, ptr);		// Get image type
fread(&width, 4, 1, ptr);		// If no comment lines, get width
while (width[0] == '#'){		//  Otherwise, ignore comment lines
	fgets(temp, 100, ptr);		//  and get width
	fread(&width, 4, 1, ptr);
}
fread(&height, 4, 1, ptr);		// Get height
const int WIDTH = atoi(width);
const int HEIGHT = atoi(height);
int ImgArray[HEIGHT][WIDTH];		// Create image array
fread(&numcol, 4, 1, ptr);		// Get number of colors (255)
for (r = 0; r < HEIGHT; r++){		// Get image data and threshold it
	for (c = 0; c < WIDTH; c++){
		data = fgetc(ptr);
		if ((data < llimit) || (data > ulimit))
			ImgArray[r][c] = 0;
		else
			ImgArray[r][c] = 90;
	}
}
fclose(ptr);				// Close image file
/*
	The following section writes out the thresholded image to a new
	PGM file.  It uses the same file header data as the image file.
*/
        strcpy(threshname, argv[1]);
        strcat(threshname, "_thrsh.pgm");
        threshptr = fopen(threshname, "wb");
        fwrite(&Type, 3, 1, threshptr);
	comment = "# New pgm file.\n";
	fwrite(&comment, 16, 1, threshptr);
	fwrite(&width, 4, 1, threshptr);	
	fwrite(&height, 4, 1, threshptr);	
	fwrite(&numcol, 4, 1, threshptr);	
        for (r = 0; r < HEIGHT; r++){
                for (c = 0; c < WIDTH; c++){
                        fputc(ImgArray[r][c], threshptr);
                }
        }
        fclose(threshptr);
}