Image Splitter — Swift source

// Image splitter — tile geometry — Swift port of the image-splitter tool.

/// One cut of the grid: the source rectangle that becomes a tile. In the
/// browser tool this rect is drawImage'd into its own canvas and encoded
/// to PNG; the geometry here is the deterministic part of that pipeline.
struct TileRect: CustomStringConvertible {
    let x: Int, y: Int, width: Int, height: Int

    var description: String { "src=(\(x), \(y)) \(width)x\(height)" }
}

enum ImageSplitter {
    /// Split a width x height image into rows x cols tiles, row-major.
    /// Mirrors splitToTiles in typescript.ts: tileW = floor(width / cols),
    /// tileH = floor(height / rows) — Int division IS Math.floor for
    /// positives, so a 1024px width over 3 cols yields 341px tiles and the
    /// last 1px column is dropped, exactly like the TS.
    static func splitTiles(width: Int, height: Int, rows: Int, cols: Int) -> [TileRect] {
        let tileW = width / cols
        let tileH = height / rows
        return (0..<rows).flatMap { row in
            (0..<cols).map { col in
                TileRect(x: col * tileW, y: row * tileH, width: tileW, height: tileH)
            }
        }
    }
}

// 1024x768 image, 2 rows x 3 cols -> six 341x384 tiles.
for tile in ImageSplitter.splitTiles(width: 1024, height: 768, rows: 2, cols: 3) {
    print(tile)
}