Writing PGM files in Python, C++, and C

Below are short codes that write gray scale PGM files in their respective languages without using any toolboxes like IPL. The output should be a salt-and-pepper image that can be  viewed in an image viewer. 

Python Code

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import array import random import sys # define the width (columns) and height (rows) of your image width = 480 height = 640 # declare 1-d array of unsigned char and assign it random values buff=array.array('B') for i in range(0, width*height): buff.append(random.randint(0,255)) # open file for writing filename = 'x.pgm' try: fout=open(filename, 'wb') except IOError, er: print “Cannot open file “, filename, “Exiting … \n“, er sys.exit() # define PGM Header pgmHeader = 'P5' + '\n' + str(width) + ' ' + str(height) + ' ' + str(255) + '\n' # write the header to the file fout.write(pgmHeader) # write the data to the file buff.tofile(fout) # close the file fout.close()

Successfully tested in Ubuntu 10.10 and Python 2.6.6

C++ Code

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#include <cstdlib> #include <fstream> #include <iostream> #include <string> using namespace std; typedef unsigned char uchar; int main(int argc, char *argv[]) { string filename = argv[1]; // define image dimensions unsigned short width = 480; unsigned short height = 640; // allocate memory for your data unsigned char *buff = new unsigned char[width*height*sizeof(uchar)]; for (int i = 0; i < width*height; i++) buff[i] = rand() % 256; // output file streams ofstream fout (filename.c_str()); if (!fout.is_open()) { cout << "Can't open output file" << filename << endl; exit(1); } // write the header fout << "P5\n" << width << " " << height << " 255\n"; // write the data fout.write((char *)buff, width*height*sizeof(uchar)); // close the stream fout.close(); // free memory delete[] buff; // return return 0; }

Successfully tested in Ubuntu 10.10 and g++ 4.4.5

C Code

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#include <stdio.h> #include <stdlib.h> typedef unsigned char uchar; int main (int argc, char* argv[]) { /* define image dimensions */ unsigned short width = 480; unsigned short height = 640; /* allocate memory for your data */ unsigned char *buff = (uchar *) malloc (width*height*sizeof(uchar)); /* assign random data to the array */ int i; for (i = 0; i < width*height; i++) buff[i] = rand() % 256; /* open output file */ FILE* image = fopen(argv[1], "wb"); if (image == NULL) { fprintf(stderr, "Can't open output file %s!\n", argv[1]); exit(1); } /* write the header */ fprintf(image, "P5\n%u %u 255\n", width, height); /* write the array */ fwrite(buff, 1, width*height*sizeof(unsigned char), image); /* close the file */ fclose(image); /* free memory */ free(buff); /* return */ return 0; }

Successfully tested in Ubuntu 10.10 and gcc 4.4.5