Set the transparency color when exporting SVGs to Bitmap using TSVGIconImage-CodePudding

I use TSVGImageIcon to read SVG vector images, and I have created this routine to save an image as a bitmap of a certain size :

function SVG2Bitmap(Imatge: TBytes; x, y: integer): TBytes;
var SVG: TSVGIconImage;
    Stream: TBytesStream;
    Bitmap: TBitmap;
    Resultat: TBytesStream;
    Form: TForm;
begin
  try
    SVG := nil;
    Form := nil;
    Stream := nil;
    Bitmap := nil;
    Resultat := nil;
    Stream := TBytesStream.Create(Imatge);
    Stream.Position := 0;
    Form := TForm.Create(nil);  // The SVGIconImage raises an error if not inside a Form
    SVG := TSVGIconImage.Create(Form);
    SVG.Parent := Form;
    SVG.Stretch := True;
    SVG.Proportional := True;
    SVG.LoadFromStream(Stream);
    SVG.Width := x;
    SVG.Height := y;
    Bitmap := TBitmap.Create;
    Bitmap.SetSize(x, y);
    SVG.PaintTo(Bitmap.Canvas, 0, 0); 
    Resultat := TBytesStream.Create;
    Bitmap.SaveToStream(Resultat);
    Result := Resultat.Bytes;
  finally
    if Assigned(SVG) then try SVG.Free except end;
    if Assigned(Form) then try Form.Free except end;
    if Assigned(Bitmap) then try Bitmap.Free except end;
    if Assigned(Stream) then try Stream.Free except end;
    if Assigned(Resultat) then try Resultat.Free except end;
  end;
end;

It works very well, but it fills the transparent zones as grey and I would like them as white. Can you recommend of a way to export SVGs to bitmap while setting the transparency color or should I just loop through the bitmap changing the grey pixels to white ?.

Thank you.

CodePudding user response：

Turns out that the SVGIconImage uses the color of the parent container as the transparency color. So changing that Form.Color to my chosen TransparencyColor does the trick.

function SVG_2_Bitmap(ImageSVG: TBytes; x, y: integer; TransparencyColor: TColor = clWhite): TBytes;
var SVG: TSVGIconImage;
    Stream, Resultat: TBytesStream;
    Bitmap: TBitmap;
    Form: TForm;
begin
  SVG := nil;
  Form := nil;
  Stream := nil;
  Bitmap := nil;
  Resultat := nil;
  try
    Stream := TBytesStream.Create(ImageSVG);
    Form := TForm.Create(nil);
    Form.Color := TransparencyColor;
    SVG := TSVGIconImage.Create(Form);
    SVG.Parent := Form;
    SVG.Proportional := True;
    SVG.LoadFromStream(Stream);
    SVG.Width := x;
    SVG.Height := y;
    Bitmap := TBitmap.Create;
    Bitmap.SetSize(x, y);
    SVG.PaintTo(Bitmap.Canvas, 0, 0);
    Resultat := TBytesStream.Create;
    Bitmap.SaveToStream(Resultat);
    Result := Resultat.Bytes;
  finally
    try SVG.Free except end;
    try Form.Free except end;
    try Bitmap.Free except end;
    try Stream.Free except end;
    try Resultat.Free except end;
  end;
end;

Thanks for all your suggestions.