Delphi - convert bmp to png fails

Question

I have the following simple code to convert clipboard image to bmp and then to png:

if Clipboard.HasFormat(CF_PICTURE) then
begin
    bitmap := TBitmap.Create;
    png := TPNGImage.Create;
    try
        bitmap.Assign(Clipboard);
        bitmap.SaveToFile(ExtractFilePath(application.ExeName) + '\filename.bmp');
        png.Draw(bitmap.Canvas, Rect(0, 0, bitmap.Width, bitmap.Height));
        png.SaveToFile(extractfilepath(application.ExeName) + '\filename.png');
    finally
        bitmap.free;
        png.free;
    end;
end;

While the conversion to bmp works and I can even open it in mspaint and see its content, the conversion to png fails and I have a blank png image. What am I doing wrong?

Answer 1

You have not set the dimensions (height and width) of the PNG image object. You would need to do that before drawing to it.

Easier however would be a simple assignment:

png.Assign(Bitmap);