Show a scrimage image in Kotlin (Mac only)

build.gradle

plugins {
    id 'java'
    id 'org.jetbrains.kotlin.jvm' version '1.3.61'
}

group 'mygroup'
version '1.0-SNAPSHOT'

sourceCompatibility = 1.8

repositories {
    mavenCentral()
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
    implementation "com.sksamuel.scrimage:scrimage-core:4.0.5"
}

compileKotlin {
    kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

ShowImage.kt

import com.sksamuel.scrimage.ImmutableImage
import com.sksamuel.scrimage.nio.PngWriter
import java.io.File

// Show image
// Implementation based on:
// https://github.com/python-pillow/Pillow/blob/77c098b01ffd599ec555d22ac76fd16563f4946f/src/PIL/ImageShow.py#L150-L162
fun ImmutableImage.show() {
    // Save image to a temp file
    val f = File.createTempFile("tmp", ".png")
    output(PngWriter(), f)
    val commandStr = "open -a Preview.app $f; sleep 20; rm -f $f"
    Runtime.getRuntime().exec(arrayOf("/bin/sh", "-c", commandStr))
}

fun main() {
    val im = ImmutableImage.loader().fromFile(File("images/dolphin.jpg"))
    im.show()
}