wxImage and draw raw rgb bytes

Question

I am programming image viewer as school task and I cant use any libraries for reading or manipulating images. First I started with bmp format. I have created class for handle this type of file. As GUI framework I am using wxWidgets.

So I have plain rgb bytes array, prepared for wxImage constructor

wxImage(int width, int height, unsigned char* data, bool static_data = false).

Problem is that when I convert it to wxBitmap and draw to dc it's ignoring rgb values a draw only black picture. I really do not know what could be a problem. This is my code for draw image:

DrawImage(wxDC &dc)
{
  BYTE *rgbArray = bmpFile->GetRGB();
  wxSize imageSize = wxSize(bmpFile->GetSize().w,bmpFile->GetSize().h);
  wxImage image = wxImage(imageSize, &rgbArray);
  wxBitmap bitmap = wxBitmap(image);
  dc.DrawBitmap(bitmap,5,5, false);
}

And this is on paint event:

void OnPaint(wxPaintEvent& event)
{
   wxAutoBufferedPaintDC dc(canvas);
   dc.SetBackground( wxBrush(canvas->GetBackgroundColour()));
   dc.Clear();
   DrawImage(dc);
}

rgbArray is filled with right values, I checked it multiple times.

Thanks for any help :)

Answer 1

Thats because you are probably calling this function, because you are passing a BYTE**.

wxImage (const wxSize &sz, bool clear=true)

to call the other overload, removing the & might help

wxImage image = wxImage(imageSize, rgbArray);

To make the code exception safe, it must be rewritten slightly. I don't know whether bmpFile returns a new buffer or a pointer to its own data buffer. If it doesn't return a new buffer then you must make your own copy because wxImage takes ownership of the buffer. see wxImage

DrawImage(wxDC &dc)
{
  wxSize imageSize = wxSize(bmpFile->GetSize().w,bmpFile->GetSize().h);
  wxImage image = wxImage(imageSize, bmpFile->GetRGB() );
  wxBitmap bitmap = wxBitmap(image);
  dc.DrawBitmap(bitmap,5,5, false);
}

or

DrawImage(wxDC &dc)
{
  std::unique_ptr<BYTE> rgbData( bmpFile->GetRGB() );
  wxSize imageSize = wxSize(bmpFile->GetSize().w,bmpFile->GetSize().h);
  wxImage image = wxImage(imageSize, rgbData.release()) );
  wxBitmap bitmap = wxBitmap(image);
  dc.DrawBitmap(bitmap,5,5, false);
}