Function recoverContainerRawSamples

pj_scene2D/core/src/codecs.cpp:476–524

}

std::optional<std::shared_ptr<std::vector<uint8_t>>> recoverContainerRawSamples(const uint8_t* data, size_t size) {
  const ImageContainer container = sniffImageContainer(data, size);
  if (container == ImageContainer::kUnknown) {
    return std::nullopt;  // not a container — caller treats the bytes as already raw
  }
  DecodedFrame staged;
  staged.pixels = std::make_shared<std::vector<uint8_t>>(data, data + size);
  const Expected<DecodedFrame> decoded =
      (container == ImageContainer::kJpeg) ? JpegCodec{}.decode(staged) : PngCodec{}.decode(staged);
  if (!decoded.has_value() || decoded->isNull() || decoded->width <= 0 || decoded->height <= 0) {
    return std::nullopt;
  }
  const DecodedFrame& frame = *decoded;
  const size_t samples = static_cast<size_t>(frame.width) * static_cast<size_t>(frame.height);
  auto out = std::make_shared<std::vector<uint8_t>>();
  switch (frame.format) {
    case PixelFormat::kMono16:
      // 16-bit grayscale already IS the flat 2-byte-per-sample buffer.
    case PixelFormat::kMono8:
      *out = *frame.pixels;
      break;
    case PixelFormat::kRGB888:
    case PixelFormat::kBGR888: {
      // PngCodec expands 8-bit grayscale to RGB (R==G==B); collapse to the luma byte.
      if (frame.pixels->size() < samples * 3) {
        return std::nullopt;
      }
      out->resize(samples);
      for (size_t i = 0; i < samples; ++i) {
        (*out)[i] = (*frame.pixels)[i * 3];
      }
      break;
    }
    case PixelFormat::kRGBA8888:
    case PixelFormat::kBGRA8888: {
      if (frame.pixels->size() < samples * 4) {
        return std::nullopt;
      }
      out->resize(samples);
      for (size_t i = 0; i < samples; ++i) {
        (*out)[i] = (*frame.pixels)[i * 4];
      }
      break;
    }
    default:
      return std::nullopt;  // YUV/NV12/DepthR32F aren't container-wrapped raw frames
  }
  return out;
}

}  // namespace PJ