copyExpandCanvas does not add transparent background?

[tzkabir]

Hi all - a little perplexed, but I'm trying to reposition an image using copyExpandCanvas. My goal is to add transparent space around a transparent background PNG to make it center horizontially, and about 1/3 vertically. But what I'm finding is that copyExpandCanvas is adding pixels which are not transparent (alpha:0). I tried to explicitly add backgroundColor: img.ColorRgba8(255, 255, 255, 0) but that doesn't help either. Also, when I use ImageGallerySaver.saveImage, it saves as a jpg and not a png?

My code (pardon how verbose it is) is as follows:

  // returns an image that is readily cropped and good to use
  final image = img.decodeImage(inputImage);
  // print(image!.hasAlpha);

  final croppedImage = img.trim(image!, mode: img.TrimMode.transparent, sides: img.Trim.all);
  // print(croppedImage!.hasAlpha);
  
  final paddedImage = img.copyExpandCanvas(
    croppedImage!,
    newWidth: (croppedImage.width*1.4).floor(),
    newHeight: croppedImage.height,
    position: img.ExpandCanvasPosition.center,
    backgroundColor: img.ColorRgba8(255, 255, 255, 0)
  );

  final paddedImage2 = img.copyExpandCanvas(
    paddedImage.convert(numChannels: 4),
    newWidth: paddedImage.width,
    newHeight: (paddedImage.height*1.4).floor(),
    position: img.ExpandCanvasPosition.bottomCenter,
    backgroundColor: img.ColorRgba8(255, 255, 255, 0)
  );

  final paddedImage3 = img.copyExpandCanvas(
    paddedImage2.convert(numChannels: 4),
    newWidth: paddedImage2.width,
    newHeight: (paddedImage2.height*1.1).floor(),
    position: img.ExpandCanvasPosition.topCenter,
    backgroundColor: img.ColorRgba8(255, 255, 255, 0)
  );

  final squaredImage = img.copyExpandCanvas(
    paddedImage3.convert(numChannels: 4),
    newWidth: max(paddedImage3.width, paddedImage3.height),
    newHeight: max(paddedImage3.width, paddedImage3.height),
    position: img.ExpandCanvasPosition.center,
    backgroundColor: img.ColorRgba8(255, 255, 255, 0)
  );

  final resizedImage = img.copyResize(squaredImage.convert(numChannels: 4), width: 2048);

  // Uint8List? bytes = await img.executeCommandBytes(squaredImage);

  Uint8List? bytes = img.encodePng(resizedImage);

  return bytes;

This is the image I put in:

And here is how it outputs:

Additionally, when I use backgroundColor: img.ColorRgba8(0, 0, 0, 0), I get the following - it's not a transparent background:

I want the background to remain as transparent. Your help is greatly appreciated!

Cheers

[tzkabir]

Wait - could it be related to this?: #624