generateSolidColorAtlasPixels function Assets and loading

Uint8List generateSolidColorAtlasPixels({ required List<Vector4> tileColors, required int columns, required int tileSize, int padding = 0, })

Builds RGBA8888 pixels (row-major, top-left origin) for a placeholder grid atlas laid out to match a TextureAtlas with the same columns, tileSize, and padding. Each tile's whole cell (content plus padding gutter) is filled with its solid color from tileColors ((r, g, b, a) in [0, 1]), so a tile never bleeds into its neighbor. Cells past tileColors.length are left transparent.

This is a stand-in for a real texture pack: generate the pixels, upload them to a gpu.Texture, and hand that to a TextureAtlas. Useful for tests and for bringing up the atlas path before final art exists.

Implementation

Uint8List generateSolidColorAtlasPixels({
  required List<Vector4> tileColors,
  required int columns,
  required int tileSize,
  int padding = 0,
}) {
  assert(columns > 0);
  assert(tileSize > 0);
  assert(padding >= 0);
  final rows = (tileColors.length / columns).ceil();
  final cell = tileSize + 2 * padding;
  final width = columns * cell;
  final height = rows * cell;
  final pixels = Uint8List(width * height * 4); // Zero-filled = transparent.
  for (var i = 0; i < tileColors.length; i++) {
    final color = tileColors[i];
    final r = (color.x * 255.0).round().clamp(0, 255);
    final g = (color.y * 255.0).round().clamp(0, 255);
    final b = (color.z * 255.0).round().clamp(0, 255);
    final a = (color.w * 255.0).round().clamp(0, 255);
    final x0 = (i % columns) * cell;
    final y0 = (i ~/ columns) * cell;
    for (var y = y0; y < y0 + cell; y++) {
      var p = (y * width + x0) * 4;
      for (var x = 0; x < cell; x++) {
        pixels[p++] = r;
        pixels[p++] = g;
        pixels[p++] = b;
        pixels[p++] = a;
      }
    }
  }
  return pixels;
}