A few simple ImageMagick 7.0+ scripts to aid textures through CLI

texture.sh

#!/bin/bash

# quit on error
set -e

# test if you have ImageMagick
[ ! $(LC_ALL=C type -t magick) ] && echo -e "missing \"magick\", please install ImageMagick 7.0+ to use this" && exit 1

HelpMe="The purpose of this script is, allow management and aid of specific formats to a common format, PNG.
And why don't use and editor like PhotoShop, GIMP or Krita?
  Simple, I don't wanna touch the gamma correction and preserve much as possible information.
   This script also allow be used as loop/batch, which makes a good option for many files.

usage:
\t${0##*/} <option> <image>\n\n

<split> <image>
This option will separatate the image each channel to a separated image with _channel.png post fix
  alias: [split|separate|separate|separar]

<as> <image>
Save a new image with only alpha information
  alias: [splitalpha|alphasplit|sa|separealpha]

<ja> <image> <image2>
Discart <image> Alpha Channel and composite/bind/add Alpha Channel from <image2> argument
  alias: [join|addalpha|alpha]

<solid> <px> <#RGB> <png>
Write a RGB Hex solid color to <png>
  alias: [color|cor]

<swap> <image>
Swap Red and Green colors of the said <image>

<inv> <image>
Invert all channels
  alias: [invertnormal|normal|invertall|negateall]

<invb> <image>
Invert Blue Channel
  alias: [invertnormalb|normalb|invertb|negateb]

<invg> <image>
Invert Green Channel
  alias: [invertnormalg|normalg|invertg|negateg]

<invr> <image>
Invert Red Channel
  alias: [invertnormalr|normalr|invertr|negater]

<inva> <image>
Invert Alpha Channel
  alias: [invertnormala|normala|inverta|negateal]

<puregrey> <image>
Convert RGB to average greyscale RGB values
  alias: [pgrey|avggrey|averagegrey|midgrey|avgrgb]

<modulategrey> <image>
Set RGB saturation to zero
  alias: [mgrey|modulate2grey|2grey]

<lumagrey> <image>
Convert RGB values to rec601luma
  alias: [2luma|grey]

<noalpha> <image>
Set image's -alpha off
  alias: [removealpha]

<combinergba> <image> <red> <green> <blue> <alpha>
Will compute <red>, <green>, <blue> and optionaly <alpha> input images then write to <image>
  alias: [combine|merge]"

# store the image input
img="${2}"

# HACK: workaround the "wontfix" TGA problem
# https://github.com/ImageMagick/ImageMagick/issues/3844 
tex_edit() {
  magick "${img}" -auto-orient "${@}"
}

case "${1}" in
  splita*|alphas*|as*|sa*|separealpha)
    tex_edit -channel A -separate "${img::-4}_alpha.png"
  ;;
  split|separ*|strip)
    tex_edit -channel R -separate "${img::-4}_red.png"
    tex_edit -channel G -separate "${img::-4}_green.png"
    tex_edit -channel B -separate "${img::-4}_blue.png"
    tex_edit -channel A -separate "${img::-4}_alpha.png"
  ;;
  join|adda*|alpha|ja)
    if [ "${3}" ] ; then
      alpha="${3}"
      #magick "${img}" \( "${alpha}" -colorspace gray \) -alpha off -compose copy_opacity -composite result
      tex_edit "${alpha}" -alpha off -compose CopyOpacity -composite "${img%%.*}_out.png"
    else
      echo -e "${HelpMe}"
    fi
  ;;
  solid|col*|cor)
    px=${2}
    RGB=${3###}
    img=${4%%.png}
    magick -size ${px}x${px} xc:"#${RGB}" "${img}.png"
  ;;
  swap)
    tex_edit -separate -swap 0,2 -combine "PNG32:${img%%.*}.png"
  ;;
  inv|invertnormal|normal|invertall|negateall)
    tex_edit -negate "${img%%.*}_out.png"
  ;;
  invb|invertnormalb|normalb|invertb*|negateb*)
    tex_edit -channel b -negate "${img%%.*}_out.png"
  ;;
  invg|invertnormalg|normalg|invertg*|negateg*)
    tex_edit -channel g -negate "${img%%.*}_out.png"
  ;;
  invr|invertnormalr|normalr|invertr*|negater*)
    tex_edit -channel r -negate "${img%%.*}_out.png"
  ;;
  inva|invertnormala|normala|inverta*|negateal*)
    tex_edit -channel a -negate "${img%%.*}_out.png"
  ;;
  puregrey|pgrey|avggrey|averagegrey|midgrey|avgrgb)
    tex_edit -fx '(r+g+b)/3' "${img%%.*}_avg_grey.png"
  ;;
  modulategrey|mgrey|modulate2grey|2grey)
    tex_edit -modulate 100,0 "${img%%.*}_modulate_grey.png"
  ;;
  lumagrey|2luma|grey)
    tex_edit -grayscale rec601luma "${img%%.*}_luma_grey.png"
  ;;
  noalpha|removealpha)
    tex_edit -alpha off "${img%%.*}_no_alpha.png"
  ;;
  combine*|merge*)
    red="${3}"
    green="${4}"
    blue="${5}"
    [ -n "${6}" ] && alpha="${6}" || magick -size 4x4 xc:"#FFFFFF" "/tmp/alpha.png" && alpha="/tmp/alpha.png"
    magick "${red}" -auto-orient "${green}" "${blue}" "${alpha}" -channel RGBA -combine "PNG32:${img%%.*}.png"
  ;;
  *) echo -e "${HelpMe}"
  ;;
esac