1. override
void debugFillDescription(List<String> description)

Accumulates a list of strings describing the current node's fields, one field per string. Subclasses should override this to have their information included in toStringDeep.

Source 

@override
void debugFillDescription(List<String> description) {
  super.debugFillDescription(description);
  description.add('image: $image');
  if (width != null)
    description.add('width: $width');
  if (height != null)
    description.add('height: $height');
  if (scale != 1.0)
    description.add('scale: $scale');
  if (color != null)
    description.add('color: $color');
  if (fit != null)
    description.add('fit: $fit');
  if (alignment != null)
    description.add('alignment: $alignment');
  if (repeat != ImageRepeat.noRepeat)
    description.add('repeat: $repeat');
  if (centerSlice != null)
    description.add('centerSlice: $centerSlice');
}