mrmBot-Matrix/natives/swirl.cc

#include <vips/vips8>

#include "common.h"

using namespace std;
using namespace vips;

char *Swirl(string type, string *outType, char *BufferData, size_t BufferLength,
            [[maybe_unused]] ArgumentMap Arguments, size_t *DataSize) {
  VOption *options = VImage::option()->set("access", "sequential");

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

  int pageHeight = vips_image_get_page_height(in.get_image());
  int nPages = vips_image_get_n_pages(in.get_image());
  int width = in.width();
  double newWidth = width * 3;
  double newHeight = pageHeight * 3;
  vector<double> divSize = {newWidth / 2, newHeight / 2};

  VImage index = VImage::xyz(newWidth, newHeight);
  VImage center = index - divSize;
  VImage polar = center
                     .copy(VImage::option()
                               ->set("format", VIPS_FORMAT_COMPLEX)
                               ->set("bands", 1))
                     .polar()
                     .copy(VImage::option()
                               ->set("format", VIPS_FORMAT_FLOAT)
                               ->set("bands", 2));

  int size = min(width, pageHeight) / 2;

  VImage test = (1 - polar.extract_band(0) / size);
  VImage degrees = test.cast(VIPS_FORMAT_FLOAT).pow(2);

  VImage angle = polar.extract_band(1) + degrees * 180;

  VImage distortion = polar.extract_band(0)
                          .bandjoin(angle)
                          .copy(VImage::option()
                                    ->set("format", VIPS_FORMAT_COMPLEX)
                                    ->set("bands", 1))
                          .rect()
                          .copy(VImage::option()
                                    ->set("format", VIPS_FORMAT_FLOAT)
                                    ->set("bands", 2)) +
                      divSize;

  vector<VImage> img;
  for (int i = 0; i < nPages; i++) {
    VImage img_frame =
        type == "gif" ? in.crop(0, i * pageHeight, width, pageHeight) : in;

    VImage distort =
        img_frame
            .gravity(VIPS_COMPASS_DIRECTION_CENTRE, newWidth, newHeight,
                     VImage::option()->set("extend", VIPS_EXTEND_COPY))
            .mapim(distortion,
                   VImage::option()->set(
                       "interpolate", VInterpolate::new_from_name("bicubic")));
    VImage frame = distort.crop(width, pageHeight, width, pageHeight);
    img.push_back(frame);
  }
  VImage final = VImage::arrayjoin(img, VImage::option()->set("across", 1));
  final.set(VIPS_META_PAGE_HEIGHT, pageHeight);

  void *buf;
  final.write_to_buffer(("." + *outType).c_str(), &buf, DataSize);

  return (char *)buf;
}