TxSprite.fromPngBytes constructor

TxSprite.fromPngBytes({ required int msgCode, required Uint8List pngBytes, })

Create a TxSprite from an indexed PNG Sprites should be PNGs with palettes of up to 2, 4, or 16 colors (1-, 2-, or 4-bit indexed palettes) Alpha channel (4th-RGBA), if present, is dropped before sending to Frame (RGB only, but color 0 is VOID) Scale to 640x400 if larger, preserving aspect ratio

Implementation

TxSprite.fromPngBytes({required super.msgCode, required Uint8List pngBytes}) {
  var imgPng = img.PngDecoder().decode(pngBytes);

  if (imgPng != null &&
      imgPng.hasPalette &&
      imgPng.palette!.numColors <= 16) {
    // resize the image if it's too big - we really shouldn't have to do this for project sprites, just user-picked images
    if (imgPng.width > 640 || imgPng.height > 400) {
      // use nearest interpolation, we can't use any interpolation that averages colors
      imgPng = img.copyResize(imgPng,
          width: 640,
          height: 400,
          maintainAspect: true,
          interpolation: img.Interpolation.nearest);
    }

    _width = imgPng.width;
    _height = imgPng.height;
    _numColors = imgPng.palette!.numColors;
    _pixelData = imgPng.data!.toUint8List();

    // we can process RGB or RGBA format palettes, but any others we just exclude here
    if (imgPng.palette!.numChannels == 3 ||
        imgPng.palette!.numChannels == 4) {
      if (imgPng.palette!.numChannels == 3) {
        _paletteData = imgPng.palette!.toUint8List();
      }
      else if (imgPng.palette!.numChannels == 4) {
        // strip out the alpha channel from the palette
        _paletteData = _extractRGB(imgPng.palette!.toUint8List());
      }

      //_log.fine('Sprite: ${imgPng.width} x ${imgPng.height}, ${imgPng.palette!.numColors} cols, ${sprite.pack().length} bytes');
    } else {
      throw Exception(
          'PNG colors must have 3 or 4 channels to be converted to a sprite');
    }
  } else {
    throw Exception(
        'PNG must be a valid PNG image with a palette (indexed color) and 16 colors or fewer to be converted to a sprite');
  }
}