Why is my bmp writer not working? - c++

Question

I'm trying to write a simple function that saves off some image data as bitmap. The data I'm generating is 3601 x 3601. I have verified in the debugger that all the data being passed to the function is correct. I have also verified that the pad size is as I would expect for a 24 bit BMP of width 3601 (padSize = 1).
The bitmap this creates is considerably larger then a bitmap I create with paint of the same dimensions meaning something here is writing too much data. I hex compared this file to a similarly sized bitmap and the headers were identical so I don't think my problem is there. I think my write command on the charbuffer must be writing more then expected, but I can't figure out why. Any help is appreciated.
void SaveBMPData(string fname, unsigned char *data, int imgWid, int imgHei)
{
ofstream file;
file.open(fname.c_str(), std::ios::out);
if (file.is_open())
{
//string fname = "APnormal.bmp";
cout << "INFO >> Saving BMP data: " << fname << "." << endl;
//write header
unsigned char fileinfo[14] = {
'B', 'M', // magic
0, 0, 0, 0, // size in bytes
0, 0, // app data
0, 0, // app data
40 + 14, 0, 0, 0 // start of data offset
};
unsigned char info[40] = {
40, 0, 0, 0, // info hd size
0, 0, 0, 0, // width
0, 0, 0, 0, // heigth
1, 0, // number color planes
24, 0, // bits per pixel
0, 0, 0, 0, // compression is none
0, 0, 0, 0, // image bits size
0x13, 0x0B, 0, 0, // horz resoluition in pixel / m
0x13, 0x0B, 0, 0, // vert resolutions (0x03C3 = 96 dpi, 0x0B13 = 72 dpi)
0, 0, 0, 0, // #colors in pallete
0, 0, 0, 0, // #important colors
};
int w = imgWid;
int h = imgHei;
int padSize = (4 - ((w * 3) % 4)) % 4;
int sizeData = w*h * 3 +h*padSize;
int sizeAll = sizeData + sizeof(fileinfo) + sizeof(info);
fileinfo[2] = (unsigned char)(sizeAll);
fileinfo[3] = (unsigned char)(sizeAll >> 8);
fileinfo[4] = (unsigned char)(sizeAll >> 16);
fileinfo[5] = (unsigned char)(sizeAll >> 24);
info[4] = (unsigned char)(w);
info[5] = (unsigned char)(w >> 8);
info[6] = (unsigned char)(w >> 16);
info[7] = (unsigned char)(w >> 24);
info[8] = (unsigned char) (h);
info[9] = (unsigned char) (h >> 8);
info[10] = (unsigned char)(h >> 16);
info[11] = (unsigned char)(h >> 24);
info[20] = (unsigned char)(sizeData);
info[21] = (unsigned char)(sizeData >> 8);
info[22] = (unsigned char)(sizeData >> 16);
info[23] = (unsigned char)(sizeData >> 24);
file.write((char*)fileinfo, sizeof(fileinfo));
file.write((char*)info, sizeof(info));
unsigned char *charbuffer = new unsigned char[w * 3 + padSize];
for (int y = 0; y<h; y++)
{
for (int x = 0; x<w; x++)
{
unsigned char red = data[(x + y*imgWid) * 3];
unsigned char green = data[(x + y*imgWid) * 3 + 1];
unsigned char blue = data[(x + y*imgWid) * 3 + 2];
charbuffer[x * 3 ] = blue;
charbuffer[x * 3 + 1] = green;
charbuffer[x * 3 + 2] = red;
}
file.write((char *)(void*)charbuffer, w*3+padSize);
}
file.close();
delete [] charbuffer;
}
else
{
cout << "can't read file.\n";
}
}

Answer 1

You need to open the file in binary mode, otherwise any pixel component with a value of 0x0a will result in a write to the file of 0x0d 0x0a.
file.open(fname.c_str(), std::ios::out | std::ios::binary);

Answer 2

Did you save the bitmap from paint as a 24 bit bmp?
I would highly suggest getting some code on the internet such as here: http://tipsandtricks.runicsoft.com/Cpp/BitmapTutorial.html and looking at/using that code.
I would avoid using arrays with values and comments (info, fileinfo) and use real concrete structs to define properties.
Your problem should be easy to figure out but IMO you are better off using some code already written since this has been done so many times.