Creating 8 bit bitmap from array of numbers - c++

Question

This has been bugging me for some time, I want to make sure that my understanding of bitmaps is correct and get some help spotting errors. Basically what I am trying to do is to save an 8 bit bitmap file and at the same time display it in a picture box in the MFC application. I want to avoid the cumbersome method of saving the bitmap then loading it up again.
The saving file operation was mostly successful, however I altered my code and now what used to be white in the file (in this instance its a black and white image) is coming out usually green but it changes. I'm guessing this is because my data is referencing information in the color table possibly, which value would be white?
HBITMAP ReadWrite::SaveFile(LPCTSTR file, double* data) {
BYTE* bmp = ConvertData(data);
HANDLE hf;
BITMAPINFO* pbmi = WriteHeader(file);
BITMAPFILEHEADER* bmfh = (BITMAPFILEHEADER*)alloca(sizeof(BITMAPFILEHEADER));
bmfh->bfType = 0x4d42; // 'BM'
bmfh->bfReserved1 = 0;
bmfh->bfReserved2 = 0;
bmfh->bfOffBits = (DWORD) sizeof(BITMAPFILEHEADER) + pbmi->bmiHeader.biSize + 256 * sizeof(RGBQUAD);
bmfh->bfSize = (DWORD)(bmfh->bfOffBits + pbmi->bmiHeader.biSizeImage);
hf = CreateFile(file, GENERIC_READ | GENERIC_WRITE, (DWORD) 0,
NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, (HANDLE) NULL );
if (hf == NULL) // error creating
{
CloseHandle (hf);
return NULL;
}
// write header
unsigned long bwritten;
if (!WriteFile(hf, (LPCVOID)bmfh, sizeof(BITMAPFILEHEADER), &bwritten, NULL))
{
CloseHandle (hf);
return NULL;
}
// write infoheader
if (!WriteFile(hf, (LPCVOID)pbmi, sizeof (BITMAPINFOHEADER) + 256 * sizeof(RGBQUAD), &bwritten, NULL ))
{
CloseHandle (hf);
return NULL;
}
// write image data
if (!WriteFile(hf, (LPCVOID)bmp_data, (int) pbmi->bmiHeader.biSizeImage, &bwritten, NULL ))
{
CloseHandle (hf);
return NULL;
}
// Close
CloseHandle(hf);
// Send back a file to display
return CreateDIBSection(NULL, pbmi, DIB_RGB_COLORS, (void**)bmp_data, NULL, 0);
}
Code to write the infoheader + palette (which should be values ranging from black to white??)
BITMAPINFO* ReadWrite::WriteHeader(LPCTSTR fn)
{
int R = ReadWrite::getR();
int C = ReadWrite::getC();
BITMAPINFO* pbmi = (BITMAPINFO*)alloca(sizeof(BITMAPINFOHEADER) + sizeof(RGBQUAD)*256);
pbmi->bmiHeader.biSize = sizeof (BITMAPINFOHEADER);
pbmi->bmiHeader.biWidth = R;
pbmi->bmiHeader.biHeight = -C;
pbmi->bmiHeader.biPlanes = 1;
pbmi->bmiHeader.biBitCount = 8;
pbmi->bmiHeader.biCompression = BI_RGB;
pbmi->bmiHeader.biSizeImage = (((R * pbmi->bmiHeader.biBitCount + 31) & ~31) >> 3) * C;
pbmi->bmiHeader.biClrUsed = 256;
pbmi->bmiHeader.biClrImportant = 0;
for(int i=0; i<256; i++)
{
pbmi->bmiColors[i].rgbRed = i;
pbmi->bmiColors[i].rgbGreen = i;
pbmi->bmiColors[i].rgbBlue = i;
pbmi->bmiColors[i].rgbReserved = 0;
}
//return true;
return pbmi;
}
And finally converting my number array into unsigned char 'Bytes':
BYTE* ReadWrite::ConvertData(double* data) {
BYTE* bmp_data;
int R = ReadWrite::getR();
int C = ReadWrite::getC();
bool binary = ReadWrite::getBinary();
bmp_data = new BYTE [R*C];
// convert the values to unsigned char (BYTE)
for(int i=0; i<R*C; i++){
if (data[i] == 1){
data[i] = 255;
}
bmp_data[i] = (unsigned char)data[i];
}
delete [] data;
return bmp_data;
}
So a recap of the issues/questions:
White comes out lime green.
The HBITMAP is unable to display inside a picturebox, the box goes solid black after setimage called (yes its set to SS_BITMAP)
I believe I may be missing some information from the creation of the bitmap and I think I need to implement a device context though I'm unsure. I can open the file in windows but if I try to upload it online it doesnt like the format.
I don't know how to manage the memory of the objects, so I'm getting leaks, how do I clean up with DeleteObject just before the application closes? (destructor of dialog maybe?) The leaks are 262144 bytes which is around the size of the image.
Thanks for reading this stupid long post.
EDIT I managed to fix the green issue (number 1), I don't know how, I think it was to do with incorrect sizes for memory on the headers. It still isn't able to upload to the internet or display in the program so something must be wrong with it.

Answer 1

So I found the issue with my code that was causing errors across other applications/the internet.
In it I assign a negative value to the height of the image in order to flip the data, however this is a completely incorrect solution. Instead:
// convert the integer values to unsigned char (BYTE) BACKWARDS
for(int i=0; i<R; i++){
for(int j=0; j<C; j++){
if (data[i*R + j] == 1 && binary){
data[i*R + j] = 255;
}
bmp_data[(R-i)*C + (j-C)] = (unsigned char)data[i*C + j];
}
}
What this does is copies the original values into the bmp_data both backwards and flipped. This ensures the data is stored correctly and will open in the application. My current solution to DIBSection and memory management was to delete all the data and reload the image from file instead. Passing a HBITMAP was too much of a chore. I would welcome input on that part, but for now all my problems are fixed.