Loading bitmaps with createfile() +CreateDIBSection

Hi, I have been trying to learn windows graphics properly, so I can do more than just using brushes & stuff. The main thing I have been trying to do, is use CreateDIBSection, I think this isn't actually needed in loading bitmaps though and is just used to either create one from scratch, or get access to the bits in the bitmap. I may still want to use this function though as it could still be useful. What I mainly want to do (right now) though, is be able to load a bitmap with CreateFie(), and then, use the bitmap with bltbit etc. Also I need to be able to add other bitmaps to the same dc? I'm thinking of a gui, where if your mouse is over something it would highlight, -ie I woud "paste" another bitmap over that part.
This is the code I've got so far for CreateFile() and CreateDIBSection.

Code:

---

switch(uiMessage)
        {
        case WM_CREATE:

        FileHandle = CreateFile(afilename,GENERIC_READ | GENERIC_WRITE,
                0,NULL,OPEN_EXISTING,0,NULL);

        FileMapping = CreateFileMapping(FileHandle,NULL,PAGE_READWRITE,
                0,0,NULL);

        //MapViewOfFile returns a void pointer
        FileHeader = (BITMAPFILEHEADER*)MapViewOfFile(FileMapping,
                FILE_MAP_WRITE,0,0,0);

        offset = FileHeader->bfOffBits;
//        outfile <<FileHeader->bfOffBits;
        return 0;

        case WM_PAINT:
        {
                        PAINTSTRUCT ps;
                        BITMAP bmp;       
                        HDC hdc = BeginPaint(hwnd, &ps);
               
                        bm=CreateDIBSection(hdc,format,DIB_RGB_COLORS,(void**)&Bits,
                        FileMapping,offset);
                       
                        GetObject(FileMapping, sizeof(bm), &bm);

                        HDC memorydc=CreateCompatibleDC(hdc);

                        HBITMAP oldbitmap=(HBITMAP)SelectObject(memorydc,bm+offset);

                        BitBlt(hdc,0,0,32,32,memorydc,0,0,SRCCOPY);

                        SelectObject(memorydc,oldbitmap);

                        DeleteDC(memorydc);

                        EndPaint(hwnd, &ps);
        return 0;

---

Thanks for any help, like I said, I did want to use DIBSection, but at the end of the day I just want to be able to load/paste bitmaps, not as resources though.
ps,
C++

By a strange coincidence I've just been trying to display bitmaps, and here's what works for me:

Code:

---

//Bitmap loading code
        ifstream file("c:\\a.bmp");

        file.seekg(10);
        dwDataOffset=GetDword(file);

        file.seekg(18);
        dwWidth=GetDword(file);

        file.seekg(22);
        dwHeight=GetDword(file);

        file.seekg(28);
        dwBitCount=GetDword(file);

        file.seekg(34);
        dwImageSize=GetDword(file);

        dwPadding=4 - ((dwWidth*(dwBitCount/8)) % 4);

        lpBits=new char[dwImageSize];

        file.seekg(dwDataOffset);
        for (DWORD i=0;i<dwImageSize;i++)
        {
                lpBits[i]=file.get();
        }

        strTemp << dwDataOffset << " "
                        << dwWidth << " "
                        << dwHeight << " "
                        << dwBitCount << " "
                        << dwPadding << " "
                        << dwImageSize;
        file.close();
}

DWORD CBitmapEx::GetDword(ifstream &file)
{
        char *lpTemp=new char[5];
        DWORD dwTemp;

        file.get(lpTemp,4);

        dwTemp=*((DWORD *)lpTemp);

        delete [] lpTemp;

        return dwTemp;
}

---

Code:

---

//Bitmap displaying code
        BITMAPINFO *lpInfo=new BITMAPINFO;
        lpInfo->bmiHeader.biSize=sizeof(BITMAPINFOHEADER);
        lpInfo->bmiHeader.biWidth=cbe.dwWidth;
        lpInfo->bmiHeader.biHeight=cbe.dwHeight;
        lpInfo->bmiHeader.biPlanes=1;
        lpInfo->bmiHeader.biBitCount=24;
        lpInfo->bmiHeader.biCompression=BI_RGB;
       
        HBITMAP hBitmap=CreateCompatibleBitmap(pDC->m_hDC,cbe.dwWidth,cbe.dwHeight);
        HDC hMemDC=CreateCompatibleDC(pDC->m_hDC);
        SetDIBits(pDC->m_hDC,hBitmap,0,cbe.dwHeight,cbe.lpBits,lpInfo,DIB_RGB_COLORS);
        hBitmap=(HBITMAP)SelectObject(hMemDC,hBitmap);
        BitBlt(pDC->m_hDC,5,5,lpInfo->bmiHeader.biWidth,lpInfo->bmiHeader.biHeight,
                                hMemDC,0,0,SRCCOPY);
        DeleteObject(SelectObject(hMemDC,hBitmap));
        DeleteDC(hMemDC);

---

You'll have to play around with that a bit, but it's all there. Good luck.

Now that you two are here together...why not use LoadImage() or even LoadBitmap() instead of messing with the file yourself?

gg

Those two functions haven't worked out for me in the past. Anyway, reading in the file myself was a good exercise, I'm not really good at that sort of thing.

Quote:

---

Now that you two are here together...why not use LoadImage() or even LoadBitmap() instead of messing with the file yourself?

---

Heh, that's what I was going to say. Seems a lot easier to me... In fact, that's even how I load bitmaps in DirectDraw :D

lol, LoadImage & LoadBitmap don't work for me either:) I don't know how to use resources!?

Benny thanks for that, I will take a look at it. The CreateFile, CreateFileMapping and MapViewOfFile do exactly (I think) , the same thing, -returns a pointer to the start of the file, except with this, windows looks after the memory management etc.

I was having a problem trying to get to the Header files, how to read them,- where are they? but I think I've got it now.
Do you have to do the SetDIBits part? My book "Graphics programming in C++" (for windows) -Mark Walmsley, doesn't have that in it at all, it does say though, that the last two params of CreateDiBSection, "cause the file image bits to be incorporated into the new bitmap".- I presume that would mean the file you have just loaded?

In case you might find it useful CreateDiBSection() allows you to get a pointer to the actual pixels, so you can change them/do things with them.

On the subject of loading/reading files, does this mean you could do something similar with any type of file? I got really confused with the whole bit, but being able to read files like this could be quite useful. Have you any tips on the best ways to do it.

Code:

---

HBITMAP hBmp = (HBITMAP)::LoadImage(NULL, "avatar.bmp", IMAGE_BITMAP,
                                    0, 0, LR_LOADFROMFILE | LR_CREATEDIBSECTION);
if (hBmp == NULL)
{
    // Handle error
}//if

// hBmp can now be selected into a compatible memory DC and bit-blit'd

---

gg

>>I don't know how to use resources!?
You don't need to - see Codeplug's code above. But if you want to, you insert a Bitmap resource, then save the script file (go save all), then #include "resource.h"... then where it asks for a resource put MAKEINTRESOURCE(*whatever the resource was called*).

*Edit: That's how it works in MSVC, I don't know how you would do it in other IDE's (or how you would do it manually for that matter :D You can look it up though, should be a 2-second google.)