spawn-blocks.png, spawn-cube-blocks.png, spawn-wall-blocks.png and
terrain/terrain-blocks.png

Source: these texture strips are adapted from Pixel Perfection CE
(https://github.com/Athemis/PixelPerfectionCE), originally by XSSheep and
updated by the Pixel Perfection CE contributors, licensed under Creative
Commons Attribution-ShareAlike 4.0 International
(https://creativecommons.org/licenses/by-sa/4.0/).

Changes made to the original textures:
- Each texture is cut to a single 16x16 tile; animated textures keep only
  their first frame.
- Textures that Minecraft colours at runtime were given a fixed tint: grass,
  leaves (with separate spruce and birch tints), vines, ferns, lily pads and
  water.
- The grass block side has its grass overlay composited onto it.
- Transparency is flattened: cut-out textures such as leaves and glass are
  laid over an opaque, darker version of their own average colour. Plant
  textures drawn as crossed planes (flowers, grass, ferns, saplings,
  mushrooms, bamboo leaves) keep their transparency; their transparent
  pixels take the plant's average colour.
- Tall grass and large fern textures get the same fixed tint as grass.
- The selected tiles are packed into one vertical strip per model.

Licence of the adaptation: the adapted textures in these strips, and the
images of the textured spawn model rendered from them (including
spawn-poster.webp), are licensed under Creative Commons Attribution-ShareAlike
4.0 International (https://creativecommons.org/licenses/by-sa/4.0/).

The strips are generated by fabriccraft-ops scripts/spawn-model (textures.py).