Encode text in a BMP image format

bmp.c

//because I can...
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>


int main(int argc, char **argv) {

	if(argc != 3)
		printf("%s <input-file> <output-file>\n", argv[0]);

	FILE *input_file, *output_file;
	long size;
	char *buffer;
	size_t result;

	input_file = fopen(argv[1], "rb");
	if(input_file == NULL) { fputs ("File error", stderr); exit(1); }

	fseek(input_file, 0, SEEK_END);
	size = ftell(input_file);
	rewind(input_file);

	buffer = (char*)malloc(sizeof(char)*size);
	if (buffer == NULL) { fputs("Memory error", stderr); exit (2); }

	result = fread(buffer, 1, size, input_file);
	if (result != size) { fputs("Reading error", stderr); exit(3); }

	
	uint8_t header[54] = 
		{ 
			'B', 'M', 	//2		signature
			0,0,0,0,	//6		size of BMP file in bytes
			0,0,		//8  	reserved must be zero
			0,0,		//10	reserved must be zero
			54,0,0,0,	//14	offset to start of image data
			40,0,0,0,	//18	size of BITMAPINFOHEADER structure, must be 40
			0,0,0,0,	//22	image width in pixels
			0,0,0,0,	//26	image height in pixels
			1,0,		//28	number of planes in the image, must be 1
			24,0,		//30	number of pits per pixel (1, 4, 8, or 24)
			0,0,0,0		//34	compression type
						//54	useless stuff
		};
	
	//Set the image size
	header[2] = (uint8_t)(size + sizeof header);
	header[3] = (uint8_t)((size + sizeof header) >> 8);
	header[4] = (uint8_t)((size + sizeof header) >> 16);
	header[5] = (uint8_t)((size + sizeof header) >> 24);

	//Do something fance calculation for with the width/height
	header[18] = (uint8_t)(size/3);	//image width
	header[22] = (uint8_t)(1);		//image height

	output_file = fopen(argv[2], "wb");
	fwrite(header, sizeof header, 1, output_file);
	fwrite(buffer, size + sizeof header, 1, output_file);


	
	fclose(input_file);
	fclose(output_file);
	free (buffer);
	return 0;
}