erle
/
tga_encoder
2
1
Fork 0
Code Issues Pull Requests 1 Projects Releases Wiki Activity
A Minetest mod to encode TGA files
52 Commits 2 Branches 7 Tags 133 KiB
Lua 100%
Go to file
Nils Dagsson Moskopp e329052c7f
Generate TGA type 3 test textures from RGB input 		2023-10-20 01:00:47 +02:00
tools Generate TGA type 3 test textures from RGB input 2023-10-20 01:00:47 +02:00
LICENSE Initial import 2022-05-14 20:21:52 +02:00
README.md Allow encoding with B8G8R8A8 colormap 2022-05-19 18:26:41 +02:00
colormap_generator.lua Add example code for node colormap generation 2022-07-31 00:24:34 +02:00
donut.lua Partially slice 3D rendered donut along its polodial direction 2023-10-16 19:20:30 +02:00
examples.lua Do not encode images with illegal colormap indexes 2023-09-22 20:06:21 +02:00
init.lua Refactor encoding of uncompressed A1R5G5B5 images 2023-10-18 05:08:16 +02:00
logo.lua Add example code to generate TGA logo 2023-08-27 15:12:47 +02:00
mod.conf Remove author from mod.conf 2022-05-16 22:18:01 +02:00

README.md

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.