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.biHeigh t, because you already wrote a row to the file. Make it bmpinfo.biHeigh t - 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);