Editing Export Aseprite Tileset

====== This LUA script file needs to be placed in Aseprite's "scripts" folder. ======
 -- export tileset.lua
 -- Copyright (C) 2022  Daniel Tremblay
 --
 -- This file is released under the terms of the MIT license.
 
 if TilesetMode == nil then return app.alert "Use Aseprite v1.3"  end
 
 local lay = app.activeLayer
 if not lay.isTilemap then return app.alert "No active tilemap layer" end
 
 local tileset = lay.tileset
 
 local dlg = Dialog("Export Tileset")
 dlg:file{ id="filename", label="Export to Tilemap file:", save=true, focus=true,
           filename=app.fs.joinPath(app.fs.filePath(lay.sprite.filename), "tileset.png") }
  :label{ label="Number of Tiles to be exported", text=tostring(#tileset) }
 
  :separator()
  :number { id="tilemap_cols", label="Number of columns in Tilemap:", text="16" }
  :check { id="ask_overwrite", label="Ask before overwrite existing Tilemap file", selected=true }
  :check { id="tiles_extruded", label="Extrude Tiles in Tilemap", selected=false }
  :check { id="keep_sprite_frames", label="Keep generated sprite frames open", selected=false }
  :check { id="open_generated", label="Open generated Tilemap", selected=false }
 
  :separator()
  :button{ text="&Export", focus=true, id="ok" }
  :button{ text="&Cancel" }
  :show()
 
 -- Data validation
 local data = dlg.data
 if not data.ok then return end
 
 local spec = lay.sprite.spec
 local grid = tileset.grid
 local size = grid.tileSize
 
 -- Create a new sprite with the dimension of one single tile
 local newSpr = Sprite(size.width, size.height, lay.sprite.colorMode)
 
 -- give the new sprite the same palette as the source sprite
 newSpr:setPalette(lay.sprite.palettes[1])
 
 -- First copy first tile into sprite frame 1
 local tile = tileset:getTile(0)
 newSpr.cels[1].image = tile
 
 -- Then create new frame and copy each tile into a new frame of sprite
 
 for i = 1, #tileset - 1 do
   app.command.NewFrame { ["content"]="current" }
   local tile = tileset:getTile(i)
   newSpr.cels[i + 1].image = tile
 end
 
 if app.apiVersion >= 3 then
   newSpr.filename = "sprite frames"
 end
 
 -- Export sprite frames as an extruded sprite sheet
 app.command.ExportSpriteSheet{
   ui=false,
   askOverwrite=data.ask_overwrite,
   type=SpriteSheetType.ROWS,
   columns=data.tilemap_cols,
   textureFilename=data.filename,
   extrude=data.tiles_extruded,
   openGenerated=data.open_generated
 }
 
 -- Close sprite frames again
 if data.keep_sprite_frames == false then
   newSpr:close()
 end