mrmBot-Matrix/natives/invert.cc

#include <napi.h>

#include <vips/vips8>

using namespace std;
using namespace vips;

Napi::Value Invert(const Napi::CallbackInfo &info) {
  Napi::Env env = info.Env();
  Napi::Object result = Napi::Object::New(env);

  try {
    Napi::Object obj = info[1].As<Napi::Object>();
    Napi::Buffer<char> data = obj.Get("data").As<Napi::Buffer<char>>();
    string type = obj.Get("type").As<Napi::String>().Utf8Value();

    VOption *options = VImage::option()->set("access", "sequential");

    VImage in =
        VImage::new_from_buffer(data.Data(), data.Length(), "",
                                type == "gif" ? options->set("n", -1) : options)
            .colourspace(VIPS_INTERPRETATION_sRGB);
    if (!in.has_alpha()) in = in.bandjoin(255);

    VImage noAlpha =
        in.extract_band(0, VImage::option()->set("n", in.bands() - 1));
    VImage inverted = noAlpha.invert();
    VImage out = inverted.bandjoin(in.extract_band(3));

    void *buf;
    size_t length;
    out.write_to_buffer(("." + type).c_str(), &buf, &length);

    result.Set("data", Napi::Buffer<char>::Copy(env, (char *)buf, length));
    result.Set("type", type);
  } catch (std::exception const &err) {
    Napi::Error::New(env, err.what()).ThrowAsJavaScriptException();
  } catch (...) {
    Napi::Error::New(env, "Unknown error").ThrowAsJavaScriptException();
  }

  vips_error_clear();
  vips_thread_shutdown();
  return result;
}