Layer.translate() makes changes in transparent area

@jazz-y 

Thank you very much for the detailed explanation.
I will try the suggestions.

Let's take a closer look at your image:

It can be seen from the histogram that in the areas that seem to be transparent, there are actually quite a large number of red pixels, their transparency is just very low.

It is important to understand how the "mask from transparency" function works - it does 2 things:

1. Sets the alpha channel value (opacity) for ALL pixels to 100%.

2. The original opacity value of the alpha channel for EACH pixel is transferred to the mask.

In other words, as a result, we get a completely opaque image and a mask that describes its initial transparency. It's not a bug, it's a feature. Watch this video to understand how it works:

During any deformation operation that leads to recalculation of pixels (translate, resize, etc.), the values of the image pixels are interpolated, that is, the brightness and transparency of closely spaced pixels are mixed - due to this, you observe the effect of adding pixels with low transparency (which become visible at the moment separating the transparency mask from the color).

To avoid this effect, you can:

a) create an opacity mask by clicking on the RGB channel icon, then increase the contrast of this mask using any brightness adjustment tools so that only 2 colors remain: black and white

b) to move the layer, instead of the translate method (which does not allow you to control the interpolation algorithm), use the transfrom method with the nearest neighbor interpolation or move (functions available through the ActionManager code)

transform(-100, -50);
function transform(horizontal, vertical) {
  var s2t = stringIDToTypeID;

  (r = new ActionReference()).putEnumerated(s2t("layer"), s2t("ordinal"), s2t("targetEnum"));
  (d = new ActionDescriptor()).putReference(s2t("target"), r);
  d.putEnumerated(s2t("freeTransformCenterState"), s2t("quadCenterState"), s2t("QCSAverage"));
  (d1 = new ActionDescriptor()).putUnitDouble(s2t("horizontal"), s2t("pixelsUnit"), horizontal);
  d1.putUnitDouble(s2t("vertical"), s2t("pixelsUnit"), vertical);
  d.putObject(s2t("offset"), s2t("offset"), d1);
  d.putEnumerated(s2t("iterfaceIconDimmed"), s2t("interpolationType"), s2t("nearestNeighbor"));
  executeAction(s2t("transform"), d, DialogModes.NO);
}

move(-100, -50);
function move(horizontal, vertical) {
	var s2t = stringIDToTypeID;
	(r = new ActionReference()).putEnumerated( s2t( "layer" ), s2t( "ordinal" ), s2t( "targetEnum" ));
	(d = new ActionDescriptor()).putReference( s2t( "target" ), r );
	(d1 = new ActionDescriptor()).putUnitDouble( s2t( "horizontal" ), s2t( "pixelsUnit" ), horizontal );
	d1.putUnitDouble( s2t( "vertical" ), s2t( "pixelsUnit" ), vertical );
	d.putObject( s2t( "to" ), s2t( "offset" ), d1 );
	executeAction( s2t( "move" ), d, DialogModes.NO );
}