Converter PNG para JPG com fundo Branco

Vcl.Graphics, Vcl.Imaging.pngimage, Vcl.Imaging.jpeg;

function PngJPG(PNG : TPngImage) : TJPEGImage;
var vBmp : TBitmap;
begin
  Result  :=  TJPEGImage.Create;
  vBmp    :=  TBitmap.Create;
  vBmp.Assign(PNG);
  Result.Assign(vBmp);
  vBmp.Free;
end;

var vPng: TPngImage; vJpg: TJPEGImage;
begin
  vPng := TPngImage.Create;
  vPng.LoadFromFile(origem);
  vJpg := PngJPG(vPng);
  vJpg.SaveToFile(destino);
  vJpg.Free;
  vPng.Free;
end;