HeLa cell images and tree crown images for Voronoi segmentation tutorial

Input dataset for the GTN tutorial titled 'Voronoi segmentation'. The dataset contains HeLa cells as an example of bioimaging data, and satellite images of trees as an example of earth observation data. 

Bioimaging data: There are two images of HeLa cells: A cell image and an image with seeds for Voronoi segmentation. These images are processed versions of original images published under licence CC BY 4.0 by Manuel Gunkel. The images have been processed respectively by normalization (for the image) and normalization and thresholding (for the seeds). 

Earth observation data: The earth observation image comes from the NeonTreeEvaluation Benchmark published under license CC BY 4.0 by Weinstein et. al. The seeds have been generated using the centre of the tree segmentation metadata provided with the image. 

References to original work: 

Gunkel, M. (2019). Microscope Image Analysis Course Sept 2109 -- Images siRNA Screen [Data set]. Zenodo. https://doi.org/10.5281/zenodo.3362976

Weinstein, B., Marconi, S., & White, E. (2022, January). Data for the NeonTreeEvaluation Benchmark (Version 0.2.2) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.5914554