Incorrect coloring of animated sprites with useFramePixels on renderTile

[richTrash21]

While testing #3413 i've encountered an issue where using useFramePixels on animated sprites would incorrectly apply color transformation. This bug affects only renderTile targets.

Here's code to reproduce this issue:

package;

import flixel.FlxSprite;
import flixel.text.FlxText;

class TestState extends flixel.FlxState
{
	var colors = [0xAA0000, 0x00AA00, 0x0000AA, 0xAAAA00, 0x00AAAA];
	var curColor = 0;

	var bugged:FlxSprite;
	var expected:FlxSprite;

	override public function create()
	{
		super.create();

		FlxG.camera.bgColor = 0xFF999999;

		add(new FlxText(50, 20, 0, "Bugged", 16));

		bugged = makeCube(30, 60);
		add(bugged);
		bugged.useFramePixels = true;

		add(new FlxText(200, 20, 0, "Expected", 16));

		expected = makeCube(180, 60);
		add(expected);

		add(new FlxText(350, 20, 0, "Graphic", 16));

		final graphic = makeCube(330, 60);
		add(graphic);

		switchColor();
		new flixel.util.FlxTimer().start(3, switchColor, 0);
	}

	override public function update(elapsed:Float)
	{
		super.update(elapsed);

		if (FlxG.keys.justPressed.Q)
			changeAlpha(-1);
		if (FlxG.keys.justPressed.E)
			changeAlpha(1);
	}

	function makeCube(x:Float, y:Float):FlxSprite
	{
		// can be just solid color sliced into frames
		final cube = new FlxSprite(x, y).loadGraphic("assets/images/cube_test.png", true, 70, 70);
		cube.setGraphicSize(120, 120);
		cube.updateHitbox();
		cube.animation.add("anim", [0, 1, 2], 8);
		cube.animation.play("anim");
		return cube;
	}

	function switchColor(?_)
	{
		final color = colors[curColor];
		bugged.color = color;
		expected.color = color;
		curColor = ++curColor % colors.length;
	}

	function changeAlpha(mult:Int)
	{
		bugged.alpha += 0.1 * mult;
		expected.alpha += 0.1 * mult;
	}
}

Running this code will result in this: applied color appear darker or as a mix of previous and current colors.

project_axyu_5QWcf0LkDa.mp4