bc5-converter

README

bc5-converter

BC5 compression/conversion tool. See the library this tool uses for more details on the implementation: https://github.com/leylandski/go-bc5

Current release: https://github.com/leylandski/bc5-converter/releases/tag/v1.0

Installation

1. Have Go (golang) installed. This was developed with 1.11.5, but earlier versions may work just as well. Use at your own risk.
2. Run go get github.com/leylandski/bc5-converter in your terminal to download the source and dependencies (https://github.com/leylandski/go-bc5) into your GOPATH.
3. Navigate to the repo directory and run go build bc5-converter.go to build the code into an executable.

Usage

Compression

This tool can convert PNG, GIF, and JPG data to a raw BC5 encoded block file.

It uses the go-bc5 library found here: https://github.com/leylandski/go-bc5 to do so. As per that implementation, it writes a 12-byte header to the start of the stream containing the DWORD/uint32 value "BC5 " in Big Endian order and two subsequent uint32 values denoting the width and height respectively, followed by the block data.

The output files are given the extension .bc5.

Decompression

The tool can also decompress .bc5 files into any of the original input formats (PNG, GIF, and JPG). When decompressing, the 12-byte header is expected or the decompression will fail. An output format must be specified if using the decompression mode, and optionally a blue component computation method. See the flags below for more details.

Program Arguments

-id, --inputdir - Specifies an input directory. All image files matching supported file type extensions will be converted.

-i, --input - Specifies an input file. Only this file will be converted.

-o, --output - Specifies an output directory to write to. If none is specified the working directory is used.

-c, --compress - Sets the mode to compress the input file into a .bc5 output file. This is the default if neither mode flag is specified.

-d, --decompress - Sets the mode to decompress the input file into the output directory in the format specified by -of.

-of, --outformat - Specifies the output format for decompression. Currently only "jpg", "gif", and "png" are supported.

-b, --blue - Specified the how the blue component is determined during decompression. Acceptable values are:

0		- Sets every output pixel's blue component to 0.
1		- Sets every output pixel's blue component to 255.
gs		- Sets every output pixel's blue component to that of its red component. Use this for greyscale images.
cn		- Sets every output pixel's blue component to the computed normal, assuming the map was normalised prior to compression.

Notes

This uses a relatively untested implementation of the BC5 algorithm. Use at your own risk. Feedback, comments, and suggestions are appreciated.

TODO

• Allow user to define their own header format.

Documentation

Overview

Main package for BC5 converter CLI tool.