Try to create Bitmap but cannot open it

[0saya0]

Hello,

I am writing a simple program that is creating a bmp file. Unfortunately it seems that my Bitmap does not contain any color data.
Where is my mistake ?

//
#pragma once
 
#include "stdafx.h"
#include <windows.h>
#include <fstream>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
 
using namespace std;
 
void wait ()
{
    std::cin.clear();
    std::cin.ignore(std::cin.rdbuf()->in_avail());
    std::cin.get();
} 
 
int main(){
 
    int i,j,r;
 
    ofstream bmpdata("BITMAP.bmp", ios::out|ios::binary); //begin stream
 
    if (!bmpdata) return 1;
 
    BITMAPINFOHEADER bmpinfo; //Infoheader Data
    bmpinfo.biSize = sizeof(BITMAPINFOHEADER);
    bmpinfo.biWidth = 256;
    bmpinfo.biHeight = 256;
    bmpinfo.biPlanes = 1;
    bmpinfo.biBitCount = 24;                                                            
    bmpinfo.biCompression = BI_RGB;
    bmpinfo.biSizeImage = 0;
    bmpinfo.biXPelsPerMeter = 0;
    bmpinfo.biYPelsPerMeter = 0;
    bmpinfo.biClrUsed = 0;
    bmpinfo.biClrImportant = 0;
 
    BITMAPFILEHEADER bmpfile;    //Fileheader Data
    bmpfile.bfType = 'Mb';
    bmpfile.bfSize = (bmpinfo.biWidth * bmpinfo.biHeight * (bmpinfo.biBitCount / 8)) + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER); //aggregate - bmpfile
    bmpfile.bfReserved1 = 0;
    bmpfile.bfReserved2 = 0;
    bmpfile.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
 
    bmpdata.write((char*)&bmpinfo, sizeof(bmpinfo));
    bmpdata.write((char*)&bmpfile, sizeof(bmpfile));
 
    RGBQUAD bmp;;
    for(r=0;r < 256; r++)   {
        bmp.rgbBlue = r;
        bmp.rgbGreen = r;
        bmp.rgbRed = r;
        bmp.rgbReserved=0;
 
      //writing directly to the file:
        bmpdata.write((char*)&(bmp.rgbBlue), sizeof(bmp.rgbBlue));
        bmpdata.write((char*)&(bmp.rgbGreen), sizeof(bmp.rgbGreen));
        bmpdata.write((char*)&(bmp.rgbRed), sizeof(bmp.rgbRed));
        bmpdata.write((char*)&(bmp.rgbReserved), sizeof(bmp.rgbReserved));
    }
 
    if(bmpinfo.biBitCount == 24) //fill image
    {
        for (i=0; i < bmpinfo.biHeight ; i++){
            for (j=0; j < bmpinfo.biWidth; j++){
                bmpdata.write((char*)&bmp, sizeof(bmp));           
            }
        }
    }
 
    bmpdata.close();
 
    cout << "Size: " << bmpfile.bfSize << "byte" << 
            " Width: " << bmpinfo.biWidth <<
            " Height: " << bmpinfo.biHeight <<
            " Blue: " << bmp.rgbBlue <<
            "\nBitmap created successfully" << endl;
    wait();
 
    return 1;
} 

thanks in advance

[boxfish]

Hi,
There are a few things that aren't right with the bitmap files your program is creating.
Firstly:
bmpfile.bfType = 'Mb'; should be bmpfile.bfType = 'MB';
Secondly:

bmpdata.write((char*)&bmpfile, sizeof(bmpfile));
bmpdata.write((char*)&bmpinfo, sizeof(bmpinfo));

You're writing these in the wrong order. Swich these two lines of code around.
Thirdly:
Don't write bmp.rgbReserved to the file. It shouldn't be there. Get rid of it in both of the places you're writing it.
Lastly:

for (i=0; i < bmpinfo.biHeight; i++)

Don't count all the way up to bmpinfo.biHeight, because you already wrote a row to the file. Make it bmpinfo.biHeight - 1
After all of that is fixed, your program should make real .bmp files.
Hope this helps.

[0saya0]

Thank your very much !

It really works now. A small milestone for me :-)

But now there is another problem. :( Take a look at the picture.

I cannot change the colors. Always this grayscale type of thing :(

Modified Code:

[...]
 
 bmpfile.bfType = 'MB';
          bmpfile.bfSize = (bmpinfo.biWidth * bmpinfo.biHeight * (bmpinfo.biBitCount / 8)) + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER); //aggregate - bmpfile
          bmpfile.bfReserved1 = 0;
          bmpfile.bfReserved2 = 0;
          bmpfile.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
 
          bmpdata.write((char*)&bmpfile, sizeof(bmpfile));
          bmpdata.write((char*)&bmpinfo, sizeof(bmpinfo));
 
 
          RGBQUAD bmp;;
          for(r=0;r < 255; r++)   {
              bmp.rgbBlue = r;
              bmp.rgbGreen = 0;
              bmp.rgbRed = 0;
              bmp.rgbReserved=0;
 
            //writing directly to the file:
              bmpdata.write((char*)&(bmp.rgbBlue), sizeof(bmp.rgbBlue));
              bmpdata.write((char*)&(bmp.rgbGreen), sizeof(bmp.rgbGreen));
              bmpdata.write((char*)&(bmp.rgbRed), sizeof(bmp.rgbRed));
          }
 
          if(bmpinfo.biBitCount == 24) //fill image
          {
              for (i=0; i < bmpinfo.biHeight-1 ; i++){
                  for (j=0; j < bmpinfo.biWidth; j++){
                      bmpdata.write((char*)&bmp, sizeof(bmp));           
                  }
              }
          }
 
          bmpdata.close();
 
          cout << "\nBitmap created successfully" << endl;
          wait();
 
          return 1;
      }
 

Best Regards

Saya

[0saya0]

Edit: bmp.Reserved also needs a value!

But this makes it impossible to create a blank red bitmap. :(

Anybody an idea ?

Edit:

solved that problem. Have to Change sizeof(bmp) to 3

bmpdata.write((char*)&bmp, 3);