#!/bin/sh
#
#------------------------------------------+
# Rewrote it like powershell.              |
#               2022/01/25 H.Kamifuji (Ja) |
#------------------------------------------+
#
# star_field [options] XxY output_image
#
# Generate a random 'hex' star field (tilable) of the size given.
#
# Options:
#    -r   angle of rotation of the hex star (def=15)
#    -b   how bright (percentage) should the stars be (def=1000)
#
####
#
# WARNING: Input arguments are NOT tested for correctness.
# This script represents a security risk if used ONLINE.
# I accept no responsiblity for misuse. Use at own risk.
#
# Anthony Thyssen    March 2006
#

Param(
    [String]$size,
    [String]$output,
    [Int]$r = 15,
    [Int]$b = 1000
    )

if ( $output -eq "" ) {
    Write-Host "Usage : star_field [-r angle] [-b bright] size output "
    Exit
}

$angle = $r
$bright = $b / 100.0

$a1 = $angle
$a2 = $a1 + 60
$a3 = $a1 + 120

$b1 = $a1 + 180
$b2 = $a2 + 180
$b3 = $a3 + 180

# Do the task (slow)...

$im6 = (gcm montage).Definition 2> -null
$im7 = (gcm magick).Definition 2> -null

if ( $im7 ) {
    $method = 1
    $magick = "magick"
}
elseif ( $im6  ) {
    $method = 2
    $magick = ""
}
else {
    echo "ImageMagick cannot be found and cannot be executed."
    Exit
}

switch ( $method ) {
    # Execute by ImageMagick7.x
    1 { magick convert -size "$size" xc: -fx 'rand()' -virtual-pixel tile `
            -colorspace Gray -sigmoidal-contrast 120x0% -negate -blur 0x.3 `
            '(' -clone 0  -motion-blur 0x10+$a1  -motion-blur 0x10+$b1 ')'  `
            '(' -clone 0  -motion-blur 0x10+$a2  -motion-blur 0x10+$b2 ')' `
            '(' -clone 0  -motion-blur 0x10+$a3  -motion-blur 0x10+$b3 ')' `
            -compose screen -background black -flatten  -normalize `
            -evaluate multiply $bright  "$output"
      }

    # Execute by ImageMagick6.x
    2 { convert -size "$size" xc: -fx 'rand()' -virtual-pixel tile `
            -colorspace Gray -sigmoidal-contrast 120x0% -negate -blur 0x.3 `
            '(' -clone 0  -motion-blur 0x10+$a1  -motion-blur 0x10+$b1 ')'  `
            '(' -clone 0  -motion-blur 0x10+$a2  -motion-blur 0x10+$b2 ')' `
            '(' -clone 0  -motion-blur 0x10+$a3  -motion-blur 0x10+$b3 ')' `
            -compose screen -background black -flatten  -normalize `
            -evaluate multiply $bright  "$output"
      }

}