writing BITMAP header

[kr47]

hi,
i am attempting to split a BITMAP file into 4 parts
in that process we have to write header for each part
how to write the header
please help me
i am in deadly need

[gpraghuram]

HI,
Tell me what you have attempted on this and where r u stuck?
Then people here can hep u...
Thanks
Raghuram

[gomanza]

Hi Guys,

hopefully you can help me. I have an array of number from 0-255 and I would like to create a bmp file, but only grey colors so 0 = schwarz , 255 = white.

I am already able to write into the file with the following method: (c++)
[PHP]
fstream data(filename, ios::'out' | ios::binary | ios::trunc);

if(!data.is_ope n() || data.bad())
{
cout << "error: cannot open file" << endl;
exit(-1);
}

writeBin(data, 'B');
writeBin(data, 'M');
writeBin(data, (long) height*width*3+ 52);
writeBin(data, (long) 0);
writeBin(data, (long) 52);

writeBin(data, (long) 40);
writeBin(data, width);
writeBin(data, height);
writeBin(data, (short) 1);
writeBin(data, (short) 8);
writeBin(data, (long) 0);
writeBin(data, (long) 0);
writeBin(data, (long) 0);
writeBin(data, (long) 0);
writeBin(data, (long) 0);
writeBin(data, (long) 0);

std::vector< pix >::iterator pixIterator = grauwert.begin( );
for (pixIterator;pi xIterator != grauwert.end(); pixIterator++)
{
printf("%i test",(*pixIter ator).grauwert) ;
writeBin(data, (*pixIterator). grauwert);
}
data.close();
[/PHP]

[PHP]
struct pix
{
pix():grauwert( 0 ),x(0),y(0) {}
int grauwert;
int x;
int y;
};

//the writing method:
template <class T>
void writeBin(fstrea m &Out, T data)
{
Out.write(reint erpret_cast<cha r*> (&data), sizeof(T));
}
[/PHP]
So my question is how can I edit my header, that I can use the numbers of my vector as numbers which indicate a grayvalue?

If you have any suggestions, please feel free to answer :-)

bye

[AdrianH]

I'll answer this tomorrow (or maybe later tonight).


Adrian

[gomanza]

Would be cool thanks

I'll answer this tomorrow (or maybe later tonight).


Adrian

[AdrianH]

Would be cool thanks

Oops, sorry. I forgot. :o :blush: So here is my response.

In the method you are describing, you have a bunch of pix objects. Can they can be in any order? If so, you will have to generate the image array prior to writing it to disk or you will have to seek around the file as you write the pixels in.

On a stylistic (and perhaps personal) note, I would recommend using BITMAPINFO and BITMAPFILEHEADE R structures, filling them in and writing these structures out to disk. This can make it easier to read and understand your code. For more information on these you can look here. The following is your code with the names of the fields put in as comments to the right:
[code=cpp]writeBin(data, 'B'); // bfType
writeBin(data, 'M');
writeBin(data, (long) height*width*3+ 52); // bfSize
writeBin(data, (long) 0); // bfReserved0
writeBin(data, (long) 52); // bfReserved1
// bfOffBits

writeBin(data, (long) 40); // blSize
writeBin(data, width); // biWidth
writeBin(data, height); // biHight
writeBin(data, (short) 1); // biPlains
writeBin(data, (short) 8); // biBitCount
writeBin(data, (long) 0); // biCompression
writeBin(data, (long) 0); // biSizeImage
writeBin(data, (long) 0); // biXPelsPerMeter
writeBin(data, (long) 0); // biYPelsPerMeter
writeBin(data, (long) 0); // biClrUsed
writeBin(data, (long) 0); // biClrImportant
[/code]

There are a few errors here. You are not supposed to fill in reserved areas. You image size is not defined. I would not use (long)40 for blSize but instead use sizeof(BITMAPIN FOHEADER). You haven’t specified bfOffBits. The list goes on.

Follow the link I provided for more information.


Adrian

[gomanza]

Hi thanks,

I resolved almost all everything, but I still have a header error (I guess). Windows says not defined bmp.

so here is my header
[PHP]
ofstream os(filename.c_s tr(), ios::out | ios::trunc | ios::binary);
if (!os.is_open()) return false;

BITMAPINFOHEADE R bmpinfo;
bmpinfo.biSize = 40;
bmpinfo.biWidth = width;
bmpinfo.biHeigh t = height;
bmpinfo.biPlane s = 1;
bmpinfo.biBitCo unt = 24;
bmpinfo.biCompr ession = 0;
bmpinfo.biSizeI mage = width * height * 3;
bmpinfo.biXPels PerMeter = 0;
bmpinfo.biYPels PerMeter = 0;
bmpinfo.biClrUs ed = 0;
bmpinfo.biClrIm portant = 0;

BITMAPFILEHEADE R bmpfile;
bmpfile.bfType = 0x4D42;
bmpfile.bfSize = sizeof(BITMAPFI LEHEADER) + sizeof(BITMAPIN FOHEADER) + (sizeof(RGB) * (width*height)) ;
bmpfile.bfReser ved1 = 0;
bmpfile.bfReser ved2 = 0;
bmpfile.bfOffBi ts = sizeof(BITMAPFI LEHEADER) + sizeof(BITMAPIN FOHEADER);

os.write((char* )&bmpfile, sizeof(bmpfile) );
os.write((char* )&bmpinfo, sizeof(bmpinfo) );
[/PHP]

!!Just a tipp!! for newbies like me :-): For saving a grayscale bmp file set RGB on the same values. For example: grayscalenumber = 55 so R = 55 G = 55 B = 55

If somebody see's an error in my header please let me know

thanks so far Gomanza

[gomanza]

And another thing

Check this out:

http://www.wotsit.org/list.asp?al=B

[AdrianH]

Hi thanks,

I resolved almost all everything, but I still have a header error (I guess). Windows says not defined bmp.

so here is my header
[code=cpp]
ofstream os(filename.c_s tr(), ios::out | ios::trunc | ios::binary);
if (!os.is_open()) return false;

BITMAPINFOHEADE R bmpinfo;
bmpinfo.biSize = 40;
bmpinfo.biWidth = width;
bmpinfo.biHeigh t = height;
bmpinfo.biPlane s = 1;
bmpinfo.biBitCo unt = 24;
bmpinfo.biCompr ession = 0;
bmpinfo.biSizeI mage = width * height * 3;
bmpinfo.biXPels PerMeter = 0;
bmpinfo.biYPels PerMeter = 0;
bmpinfo.biClrUs ed = 0;
bmpinfo.biClrIm portant = 0;

BITMAPFILEHEADE R bmpfile;
bmpfile.bfType = 0x4D42;
bmpfile.bfSize = sizeof(BITMAPFI LEHEADER) + sizeof(BITMAPIN FOHEADER) + (sizeof(RGB) * (width*height)) ;
bmpfile.bfReser ved1 = 0;
bmpfile.bfReser ved2 = 0;
bmpfile.bfOffBi ts = sizeof(BITMAPFI LEHEADER) + sizeof(BITMAPIN FOHEADER);

os.write((char* )&bmpfile, sizeof(bmpfile) );
os.write((char* )&bmpinfo, sizeof(bmpinfo) );
[/code]

!!Just a tipp!! for newbies like me :-): For saving a grayscale bmp file set RGB on the same values. For example: grayscalenumber = 55 so R = 55 G = 55 B = 55

If somebody see's an error in my header please let me know

thanks so far Gomanza

Sorry that I haven't responded to this earlier. Having problems loosing threads every so often. Please bump the thead by posting something to it if you don't get a responce after a while.

You don't have to set the grayscale value using R = 55, G=55 and B=55, just declare the bitmap as a 8 bit instead of a 24 bit bitmap. Of course, I've not used this in a while so I could be wrong. ;)

Also, include the Windows.h header file to fix the error you are referring to (unless I have misinterpreted, if so, post the message as it is outputted by the compiler).


Adrian

[gomanza]

8bit didn't work very well anyway 24bit and RGB = same number works somehow. :-)

So here is my Class
[PHP]

//Grafikfunctions .h:
#pragma once

#include <windows.h>
#include <string>
#include <vector>
#include <fstream>
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <string>
#include <ctime>

using namespace std;

struct RGB
{
BYTE blue;
BYTE green;
BYTE red;
};


class Graficfunctions
{
private:
long width;
long height;
vector<RGB> colors;
vector<RGB> tempColor;

public:
Graficfunctions ();
~Graficfunction s();

void arrayReorder();
void setPixelColor(l ong x, long y, BYTE red, BYTE green, BYTE blue);
void setPixelColor(l ong x, long y, RGB newColor);
void setWidth(long nwidth);
void setHeight(long nheight);

bool to8Bmp(std::str ing filename,int height, int width);

};

//Grafikfunctions .cpp:
#include "Graficfunction s.h"

using namespace std;

Graficfunctions ::Graficfunctio ns() {
}

Graficfunctions ::~Graficfuncti ons() {

}

void Graficfunctions ::setPixelColor (long x, long y, BYTE red, BYTE green, BYTE blue)
{
RGB newCol;
newCol.red = red;
newCol.green = green;
newCol.blue = blue;
colors.push_bac k(newCol);
}

void Graficfunctions ::setPixelColor (long x, long y, RGB newColor)
{
colors.push_bac k(newColor);
}

void Graficfunctions ::arrayReorder( ) {

}

void Graficfunctions ::setWidth(long nwidth) {
width = nwidth;
}

void Graficfunctions ::setHeight(lon g nheight){
height = nheight;
}

bool Graficfunctions ::to8Bmp(string filename,int height,int width)
{
//unsigned register long i;
ofstream os(filename.c_s tr(), ios::out | ios::trunc | ios::binary);
if (!os.is_open()) return false;

BITMAPINFOHEADE R bmpinfo;
bmpinfo.biSize = 40;
bmpinfo.biWidth = width;
bmpinfo.biHeigh t = height;
bmpinfo.biPlane s = 1;
bmpinfo.biBitCo unt = 24;
bmpinfo.biCompr ession = 0;
bmpinfo.biSizeI mage = width * height * 3+52;
bmpinfo.biXPels PerMeter = 0;
bmpinfo.biYPels PerMeter = 0;
bmpinfo.biClrUs ed = 0;
bmpinfo.biClrIm portant = 0;

BITMAPFILEHEADE R bmpfile;
bmpfile.bfType = 0x4D42;
bmpfile.bfSize = sizeof(BITMAPFI LEHEADER) + sizeof(BITMAPIN FOHEADER) + (sizeof(RGB) * (width*height)) ;
bmpfile.bfReser ved1 = 0;
bmpfile.bfReser ved2 = 0;
bmpfile.bfOffBi ts = sizeof(BITMAPFI LEHEADER) + sizeof(BITMAPIN FOHEADER);

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

//Bilddaten einfügen:
int i=0;
vector<RGB>::it erator myiteratorColor ;
for(myiteratorC olor = colors.begin(); myiteratorColor != colors.end(); myiteratorColor ++){
os.write((char* )&(*(myiterator Color)), sizeof(RGB));
i++;
}

os.close();
printf("File created\n");
return true;
}

[/PHP]

The compiler does not bring any error it works until I try to open a file with the Windows picture viewer. Can I send you such a image file?

Sorry have to leave work now I'll be back tomorrow

[AdrianH]

8bit didn't work very well anyway 24bit and RGB = same number works somehow. :-)

Hmmm, dunno. I've just dumpped entire 256 grey scale images before, but its been a while (few years). If you don't mind using 24bit colour, then I'll leave it at that. ;)

The compiler does not bring any error it works until I try to open a file with the Windows picture viewer. Can I send you such a image file?

Sure, umm, not sure. I am not aware of any method for you to send it to me. I don't post my email due to spam reasons. Maybe you can find a place to host the file for a short time?

Sorry have to leave work now I'll be back tomorrow

No prob. Its late anyway. ;)


Adrian

[gomanza]

Hi Adrian,

ok here you can download 2 of my files.
The interesting file is Graficfunctions .cpp

http://www.home.hs-karlsruhe.de/~sest0024/greyscale/

I guess 24bit are ok. You can also find a 24bit bmp and a picture that shows what my programm produces if the header is on 8bit.

gomanza

[gomanza]

I just found another possibility do you know how this works?

http://msdn2.microsoft .com/en-us/library/ms532305.aspx

[gomanza]

Sorry couldn't edit my message:

I just found another possibility do you know how this works?

http://msdn2.microsoft .com/en-us/library/ms532305.aspx

edit: ok its not that difficult, haven't tried it yet cause of time.

Another interesting thing about my putput pictures: I cannot load them with openCV. I guess it is the same problem as windows has.

I also player a little with my header configuration:
[PHP]
BITMAPINFOHEADE R bmpinfo;
bmpinfo.biSize = sizeof(BITMAPIN FOHEADER);
bmpinfo.biWidth = width;
bmpinfo.biHeigh t = -height; //minus just to mirror the picture
bmpinfo.biPlane s = 1;
bmpinfo.biBitCo unt = 24;
bmpinfo.biCompr ession = BI_RGB; //BI_RGB is 0
bmpinfo.biSizeI mage = ((((width * bmpinfo.biBitCo unt) + 31) & ~31) >> 3) * height; //width * height * 3; //width = 64 height = 48
bmpinfo.biXPels PerMeter = 0;
bmpinfo.biYPels PerMeter = 0;
bmpinfo.biClrUs ed = 0;
bmpinfo.biClrIm portant = 0;

BITMAPFILEHEADE R bmpfile;
bmpfile.bfType = 0x4D42;
bmpfile.bfSize = sizeof(BITMAPFI LEHEADER) + sizeof(BITMAPIN FOHEADER) + (sizeof(RGB) * (width*height)) ;
bmpfile.bfReser ved1 = 0;
bmpfile.bfReser ved2 = 0;
bmpfile.bfOffBi ts = sizeof(BITMAPFI LEHEADER) + sizeof(BITMAPIN FOHEADER);

[/PHP]

[gomanza]

problem half solved:

preknowledge: grayscale picture R & G & B same number!!

Yippi I just figured out by comparing the hex files of a incorrupt and a corrupt bmp file that there is a 00 after every RGB numbers:

[PHP]
// incorrupt file
4b 4b 4b 00 ff ff ff 00 ....
//corrupt file
4b 4b 4b ff ff ff
[/PHP]
-> I miss something in between :-)

so I just added another BYTE to my struct RGB. By definition this byte is 0
[PHP]
struct RGB
{
BYTE blue;
BYTE green;
BYTE red;
BYTE zero;
};
[/PHP]

The result is no longer a grayscale picture:

http://www.home.hs-karlsruhe.de/~sest0024/greyscale/strange.bmp

let's see what I can figure out

gomanza