panoramaPixels function

ByteData? panoramaPixels(Uint8List bytes)

A Radiance file as the RGBA8 EnvironmentMap.fromPanorama reads, or null when it is not one.

Clamped rather than tone-mapped. The cube is eight bits a channel — EnvironmentMap's own doc comment says why, and that this is a real limitation — so a sun four hundred times brighter than the sky around it becomes white either way. Rolling the highlights off first would darken everything else to buy detail in a region the cube cannot hold anyway, and would make the indirect light a panorama gives differ from the indirect light the same picture gives as a PNG.

Implementation

ByteData? panoramaPixels(Uint8List bytes) {
  final HdrImage image;
  try {
    image = readHdr(bytes);
  } on HdrFormatException {
    return null;
  }
  final ByteData out = ByteData(image.width * image.height * 4);
  for (var i = 0; i < image.width * image.height; i++) {
    out
      ..setUint8(i * 4, _byte(image.rgb[i * 3]))
      ..setUint8(i * 4 + 1, _byte(image.rgb[i * 3 + 1]))
      ..setUint8(i * 4 + 2, _byte(image.rgb[i * 3 + 2]))
      ..setUint8(i * 4 + 3, 255);
  }
  return out;
}