Generating a barcode BMP in c - c

Question

I've been assigned to create a barcode image from a number generated randomly by me (that I've already done). So far I tried to create a BMP file and put in a simple black and white columns but my picture is distorted by other colors and not even in columns. I didn't even start to write the barcode itself (that itself is still a mystery to me), I tried to create it for almost 2 weeks now and to no avail.. I mostly need a program that writes black or white to the program by columns or row by row so i can put black or white at will.
This is my code:
`int width, hight;
width = 141;
hight = 70;
FILE* barcode;
fopen_s(&barcode,NEWBARCODE, "wb");
int filesize = 54 + 3 * width*height; //w is your image width, h is image height, both int
char bmpfileheader[14] = { 'B','M', 0,0,0,0, 0,0, 0,0, 54,0,0,0 };
char bmpinfoheader[40] = { 0x28,0,0,0, 141,0,0,0, 70,0,0,0, 1,0, 24,0,0,0,0,0,0x8c,0x05,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
unsigned char white[3] = {255,255,255 };
unsigned char black[3] = {0,0,0 };
unsigned char pad[1] = { 0 };
bmpfileheader[2] = (unsigned char)(filesize);
bmpfileheader[3] = (unsigned char)(filesize >> 8);
bmpfileheader[4] = (unsigned char)(filesize >> 16);
bmpfileheader[5] = (unsigned char)(filesize >> 24);
fwrite(&bmpfileheader, 1, 14, barcode);
fwrite(&bmpinfoheader, 1, 40, barcode);
for (int i = 0; i < height; i++) { //columns
for (int j = 0; j < width*3+1; j++) {
if (i % 2 == 0) {
fwrite(&white, 1, 3, barcode);
fwrite(&black, 1, 3, barcode);
}
else {
fwrite(&black, 1, 3, barcode);
fwrite(&white, 1, 3, barcode);
}
}
fwrite(&pad, 1, 1, barcode);
}
and that outputs the bmp file
What is wrong? And if there are any tips to work on creating a bmp file would be greatly appreciated :)

Answer 1

Try the below. Note that I've moved the BMP to a bit depth of 32. The wrapper function setColumn will allow you to set individual columns to black or white as you see fit. Much more manageable to think of the BMP as an array that you can freely manipulate instead of having to deal with a ton of fwrite logic.
#include "stdafx.h"
#include <fstream>
#define NEWBARCODE "test.bmp"
#define WHITE 255
#define BLACK 0
void setColumn(unsigned char *data, const int height, const int width, const int colIndex, const int grayVal)
{
for (int r = 0; r < height; ++r)
{
data[r * width * 4 + colIndex * 4 + 0] = grayVal;
data[r * width * 4 + colIndex * 4 + 1] = grayVal;
data[r * width * 4 + colIndex * 4 + 2] = grayVal;
data[r * width * 4 + colIndex * 4 + 3] = 255;
}
}
int main()
{
int width, height;
width = 141;
height = 70;
std::ofstream filestream;
filestream.open(NEWBARCODE, std::ios::beg | std::ios::out | std::ios::binary);
int filesize = 54 + 4 * width * height;
char bmpfileheader[14] = { 'B','M', 0,0,0,0, 0,0, 0,0, 54,0,0,0 };
char bmpinfoheader[40] = { 0x28,0,0,0, 141,0,0,0, 70,0,0,0, 1,0, 32,0,0,0,0,0,0x8c,0x05,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 };
bmpfileheader[2] = (unsigned char)(filesize);
bmpfileheader[3] = (unsigned char)(filesize >> 8);
bmpfileheader[4] = (unsigned char)(filesize >> 16);
bmpfileheader[5] = (unsigned char)(filesize >> 24);
filestream.write(bmpfileheader, 14);
filestream.write(bmpinfoheader, 40);
//Allocate BMP data block
unsigned char *data = new unsigned char[width * height * 4]{ 0 };
//Initialize BMP data to all black pixels
for (int i = 0; i < width * height * 4; ++i)
data[i] = 0;
//Set white
for (int i = 75; i < 100; ++i)
setColumn(data, height, width, i, WHITE);
//Set white
for (int i = 15; i < 25; ++i)
setColumn(data, height, width, i, WHITE);
//Set black
for (int i = 20; i < 23; ++i)
setColumn(data, height, width, i, BLACK);
filestream.write((const char *)data, height * width * 4);
filestream.close();
delete data;
return 0;
}