go-pcx

README

PCX Encoder/Decoder Package for Go

This package implements a PCX image decoder and encoder for Go.

Documentation: https://pkg.go.dev/github.com/samuel/go-pcx/pcx

Installation

go get github.com/samuel/go-pcx/pcx

Usage

Importing the package registers PCX with image.Decode, so a program that just needs to read PCX files alongside other formats can import it for its side effects alone:

import (
	"image"

	_ "github.com/samuel/go-pcx/pcx"
)

func load(r io.Reader) (image.Image, error) {
	img, _, err := image.Decode(r)
	return img, err
}

Decoding and encoding directly:

package main

import (
	"log"
	"os"

	"github.com/samuel/go-pcx/pcx"
)

func main() {
	f, err := os.Open("in.pcx")
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()

	// The concrete type depends on the variant the file uses: *image.Paletted,
	// *image.Gray, *image.RGBA or *image.NRGBA. Use pcx.DecodeExtended instead to
	// also read the header metadata, such as DPI.
	img, err := pcx.Decode(f)
	if err != nil {
		log.Fatal(err)
	}

	out, err := os.Create("out.pcx")
	if err != nil {
		log.Fatal(err)
	}
	// pcx.Encode picks the PCX variant from the image's type and contents.
	if err := pcx.Encode(out, img); err != nil {
		log.Fatal(err)
	}
	if err := out.Close(); err != nil {
		log.Fatal(err)
	}
}

pcx.Decode reports a malformed file as a pcx.FormatError and a valid but unimplemented variant as a pcx.UnsupportedError; a file that ends early is reported as io.ErrUnexpectedEOF. pcx.Encode reports a caller mistake, such as bounds PCX cannot represent, as a plain error.

Supported variants

Bits per pixel	Planes	Decodes to	Palette
8	1	*image.Paletted, or *image.Gray when the file carries no palette and is marked grayscale	after the pixel data
1, 2, 4	1	*image.Paletted	header colormap (monochrome, CGA or EGA)
1	2–4	*image.Paletted	header colormap
8	3	*image.RGBA	—
8	4	*image.NRGBA (the fourth plane holds straight alpha)	—

Uncompressed (non-RLE) PCX files are not supported.