VoxeLibre/mods/CORE/tga_encoder/README.md
the-real-herowl b04493dcb6 Add 'mods/CORE/tga_encoder/' from commit 'aad231f5e406a7c1eaafe6595a64b9c55f230692'
git-subtree-dir: mods/CORE/tga_encoder
git-subtree-mainline: a5740f8edf
git-subtree-split: aad231f5e4
2024-03-19 19:28:16 +01:00

87 lines
2.3 KiB
Markdown
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

# tga_encoder
A TGA Encoder written in Lua without the use of external Libraries.
Created by fleckenstein for MineClone2, then improved by erlehmann.
May be used as a Minetest mod.
See `examples.lua` for example code and usage hints.
## Use Cases for `tga_encoder`
### Encoding Textures for Editing
TGA images of types 1/2/3 consist of header data followed by a pixel array.
This makes it trivial to parse TGA files and even edit pixels in-place.
No checksums need to be updated on any kind of in-place texture editing.
**Tip**: When storing an editable image in item meta, use zlib compression.
### Legacy Minetest Texture Encoding
Minetest 5.4 did not include `minetest.encode_png()` (or any equvivalent).
Since `tga_encoder` is written in pure Lua, it does not need engine support.
**Tip:** Look at `examples.lua` and the Minetest mod `mcl_maps` for guidance.
### Advanced Texture Format Control
The function `minetest.encode_png()` always encodes images as 32bpp RGBA.
`tga_encoder` allows saving images as grayscale, 16bpp RGBA and 24bpp RGB.
For generating maps from terrain, color-mapped formats can be more useful.
### Encoding Very Small Textures
Images of size 8×8 or below are often smaller than an equivalent PNG file.
Note that on many filesystems files use at least 4096 bytes (i.e. 64×64).
Therefore, saving bytes on files up to a few 100 bytes is often useless.
### Encoding Reference Textures
TGA is a simple format, which makes it easy to create reference textures.
Using a hex editor, one can trivially see how all the pixels are stored.
## Supported Image Types
For all types, images are encoded in a fast single pass (i.e. append-only).
### Color-Mapped Images (Type 1)
These images contain a palette, followed by pixel data.
* `A1R5G5B5` (8bpp RGB)
* `B8G8R8` (8bpp RGB)
* `B8G8R8A8` (8bpp RGBA)
### True-Color Images (Type 2)
These images contain uncompressed RGB(A) pixel data.
* `A1R5G5B5` (16bpp RGBA)
* `B8G8R8` (24bpp RGB)
* `B8G8R8A8` (32bpp RGBA)
### Grayscale Images (Type 3)
* `Y8` (8bpp grayscale)
### Run-Length Encoded (RLE), True-Color Images (Type 10)
These images contain compressed RGB(A) pixel data.
* `A1R5G5B5` (16bpp RGBA)
* `B8G8R8` (24bpp RGB)
* `B8G8R8A8` (32bpp RGBA)
## TODO
* Actually support `R8G8B8A8` input for `A1R5G5B5` output
* Add both zoomable and explorable maps to `mcl_maps`.