read and write a bmp file in c++ - c++

Question

i am trying to read and write a bmp file in c++.output file is created but is not opening and it's size is 257kb whereas the input file is 258kb.i first read and write the 14 byte header file,40 byte imageheader file,then the 512*512 pixels,here's my code,can anyone help please
#include <iostream>
#include <fstream>
#include <cmath>
using namespace std;
int main()
{
ifstream iFile;
char ch;
iFile.open("lena.bmp",ios::binary);
ofstream oFile;
oFile.open("lena3.bmp",ios::binary);
//int headerImageHeader=54;
// int imageHeader=40;
int fs[54];
//int ihs[imageHeader];
int tfs[54];
int pixel[512][512];
if(iFile.is_open() && oFile.is_open())
{
for(int i=0;i<54;i++)
{
iFile.get(ch);
fs[i]=ch;
cout<<fs[i]<<" ";
char p;
p=fs[i];
oFile<<p;
}
for(int w=0;w<512;w++)
{
for(int h=0;h<512;h++)
{
iFile.get(ch);
pixel[w][h]=ch;
//cout<<pixel[w][h]<<;
char pi=pixel[w][h];
oFile<<pi;
}
}
oFile.close();
iFile.close();
}
else cout << "Unable to open file"<<endl;
return 0;
}

Answer 1

Your code has multiple problems. Basically, the pixel storage in BMP file is not that simple. It depends on the type of BMP (e.g. Monochrome Bitmap, 16 Color Bitmap, 256 Color Bitmap and 24-bit Bitmap etc).
There are two options to read one Bitmap file and write it in another Bitmap file.
a) Read each byte from the source file and write in destination file
b) Understand Bitmap storage format and write code accordingly.
For option b) good source is available at wiki.
In summary, the calculation of Pixel Array storage (size) is:
PixelArraySize = RowSize x ImageHeight
Where ImageHeight is height of image in pixel. The RowSize is calculated as:
RowSize = [(BitsPerPixelxImageWidth + 31) / 32 ]x4