App Icon Generator — Kotlin source

// App Icon Generator — contain-fit, centered export geometry for the
// 16/32/180/192/512 icon set.
//
// Language: Kotlin (1.9, standard library only)
// Source:   CosmoDev polyglot showcase port, from the authored TypeScript
//           snippet src/tool-sources/app-icon-generator/typescript.ts.

import kotlin.math.roundToInt

/** One export target: the square canvas edge and the centered contain-fit
 *  rect the source image is drawn into. */
data class IconRect(val size: Int, val x: Int, val y: Int, val w: Int, val h: Int)

object AppIconGeometry {

    val defaultSizes: IntArray = intArrayOf(16, 32, 180, 192, 512)

    /** The deterministic half of the tool: per export size, the contain-fit
     *  rect (scale = min(px/w, px/h), clamped to >= 1) plus the centered draw
     *  offset — the geometry the TS pipeline feeds ctx.drawImage before
     *  canvas.toBlob PNG-encodes each square. Bitmap decode and PNG encode
     *  stay with the host. roundToInt rounds ties toward positive infinity,
     *  matching JS Math.round on these non-negative values. */
    fun iconSetPlan(srcW: Int, srcH: Int, sizes: IntArray = defaultSizes): List<IconRect> =
        sizes.map { px ->
            val scale = minOf(px.toDouble() / srcW, px.toDouble() / srcH)
            val w = (srcW * scale).roundToInt().coerceAtLeast(1)
            val h = (srcH * scale).roundToInt().coerceAtLeast(1)
            IconRect(
                px,
                ((px - w) / 2.0).roundToInt(), // letterbox on transparency
                ((px - h) / 2.0).roundToInt(),
                w,
                h,
            )
        }
}