CODEWITHSUNDEEP
c++winapibitmapgdi+save
Raven
Raven

Reputation: 4903

saving to bitmap with win32 API or GDI+

Question is rather simple but I couldn't find nice & clean solution to my problem on the Internet. What I got are some drawings on my window. Now, I can save those using BitBlt function from window device context to image device context, and also from there to bitmap handle:

HDC bitmapDC = CreateCompatibleDC(dc);
HBITMAP bitmap = CreateCompatibleBitmap(bitmapDC, 200, 200);
SelectObject(bitmapDC,bitmap);
BitBlt(bitmapDC, 0, 0, 200, 200, dc, 200, 200, SRCCOPY);

But from there I'm lost. I had a look at GDI+ Bitmap class which got save function, and I found how to implement code for retrieving CLSID of picture encoding. However I don't know if I use loading to that class correctly. There's overloaded constructor for HBITMAP, but it's also asking for some palette, which I set to NULL:

Bitmap image(bitmap,NULL);

I tried to save png file but it resulted in black quare without those drawings I was expecting. If you'd like, full code for my painting procedure:

void GetCLSID(const WCHAR* format, CLSID* pClsid){
    UINT  num = 0;          // number of image encoders
    UINT  size = 0;         // size of the image encoder array in bytes

    ImageCodecInfo* pImageCodecInfo = NULL;

    GetImageEncodersSize(&num, &size);

    pImageCodecInfo = (ImageCodecInfo*)(malloc(size));

    GetImageEncoders(num, size, pImageCodecInfo);

    for(UINT j = 0; j < num; ++j)
    {
      if( wcscmp(pImageCodecInfo[j].MimeType, format) == 0 )
      {
         *pClsid = pImageCodecInfo[j].Clsid;
         free(pImageCodecInfo);
      }    
    }
}

void OnPaint(HDC dc){
    RECT rect; rect.bottom = 0; rect.top = 20; rect.left = 0; rect.right = 100;
    HBRUSH blueBrush = CreateSolidBrush(RGB(0,0,200));
    FillRect(dc, &rect, blueBrush);

    Graphics graphics(dc);
    Pen      pen(Color(255, 0, 0, 255));
    graphics.DrawLine(&pen, 0, 0, 200, 100);

    SolidBrush greenBrush(Color(0,200,0));
    Rect ellipseRect(20,20,20,20);
    graphics.FillEllipse(&greenBrush, ellipseRect);

    SolidBrush redBrush(Color(200,0,0));
    Rect boxRectangle(0,40,20,100);
    graphics.FillRectangle(&redBrush, boxRectangle);

    pen.SetColor(Color(200,0,200));
    pen.SetWidth(20);
    graphics.DrawBezier(&pen, 100, 20, 130, 40, 200, 10, 230, 20);

    HDC bitmapDC = CreateCompatibleDC(dc);
    HBITMAP bitmap = CreateCompatibleBitmap(bitmapDC, 200, 200);
    SelectObject(bitmapDC,bitmap);
    BitBlt(bitmapDC, 0, 0, 500, 500, dc, 500, 500, SRCCOPY);

    Bitmap image(bitmap,NULL);
    CLSID clsID;
    GetCLSID(L"image/png", &clsID);
    image.Save(L"pic.png", &clsID);

}

I couldn't even imagine that simple saving will be such problem, so I'll be glad for any help, thanks!

Upvotes: 0

Views: 11015

Answers (1)

Mike Kwan
Mike Kwan

Reputation: 24477

I gave code here which does pretty much what you want: How to save the client area of a child Window to a Bitmap file?

It is very verbose in C. It's a lot better in C++ because of CImage

Upvotes: 2

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