Aseprite exporter for texture atlas files

export-atlas.lua

------------------------------------------------------------------------
-- Export texture atlas file format
--
-- The file format is as follows:
--
-- # version VERSION_NUMBER
-- # ASEPRITE_FILE
-- i IMAGE_FILE NUMBER_OF_FRAMES
-- s SPRITE_X SPRITE_Y SPRITE_W SPRITE_H SPRITE_PIVOT_X SPRITE_PIVOT_Y
-- a ANIM_NAME ANIM_START ANIM_END ANIM_DIRECTON ANIM_FRAME_TIME_SECONDS
--
-- Do not use spaces in filenames!
-------------------------------------------------------------------------

local Version = 1
local json = dofile("lib/json.lua")

local function renameWithExtension(path, extension)
    return app.fs.filePathAndTitle(path) .. "." .. extension
end

local function tempJsonFilename(filename)
    return app.fs.joinPath(app.fs.tempPath, app.fs.fileTitle(filename) .. ".json")
end

local function nextPowerOfTwo(value)
    return 2 ^ math.ceil(math.log(value) / math.log(2))
end

local function exportSpriteSheet(sprite, trimSprites, showUI, imFormat, w, h)
    app.command.ExportSpriteSheet {
        ui              = showUI,
        askOverwrite    = false,
        type            = SpriteSheetType.PACKED,
        columns         = 0,
        rows            = 0,
        width           = w,
        height          = h,
        bestFit         = false,
        textureFilename = renameWithExtension(sprite.filename, imFormat),
        dataFilename    = tempJsonFilename(sprite.filename),
        dataFormat      = SpriteSheetDataFormat.JSON_ARRAY,
        borderPadding   = 0,
        shapePadding    = 0,
        innerPadding    = 0,
        trim            = trimSprites,
        extrude         = false,
        openGenerated   = false,
        layer           = "",
        tag             = "",
        splitLayers     = false,
        listLayers      = true,
        listTags        = true,
        listSlices      = true
    }
end

local function spriteSheetSize(sprite)
    local atlasInput = io.open(tempJsonFilename(sprite.filename), "r")

    if atlasInput == nil then
        app.alert("Error: Could not open sprite sheet json file")
        return
    end

    local data = json.decode(atlasInput:read("a"))
    return {width = data.meta.size.w, height = data.meta.size.h}
end

local function exportAtlasFile(sprite, imFormat, pivotX, pivotY)
    local atlasFilename = renameWithExtension(sprite.filename, "atlas")
    local textureFilename = app.fs.fileTitle(sprite.filename) .. "." .. imFormat

    local atlasOutput = io.open(atlasFilename, "w+")
    local atlasInput = io.open(tempJsonFilename(sprite.filename), "r")

    if atlasInput == nil then
        app.alert("Error: Could not open sprite sheet json file %s")
        return
    end

    local data = json.decode(atlasInput:read("a"))
    io.output(atlasOutput)

    -- Header
    io.write("# version" .. Version .. "\n")
    io.write("# " .. app.fs.fileName(sprite.filename) .. "\n")
    io.write(string.format("i %s %d\n", textureFilename, #data.frames))

    -- Frames
    for i, v in ipairs(data.frames) do
        io.write(string.format("s %d %d %d %d %.2f %.2f\n",
            v.frame.x, v.frame.y, v.frame.w, v.frame.h, pivotX, pivotY))
    end

    -- Animations
    local animationFrames = 0;
    local directionMap = {forward = "Forward", pingpong = "PingPong"}
    for i, v in ipairs(data.meta.frameTags) do
        local name = v.name:gsub(" ", "_")
        local direction = directionMap[v.direction]
        local frameTimeS = data.frames[v.from + 1].duration / 1000.0

        if direction == nil then
            app.alert("Warning: Animation direction %s is not supported", v.direction)
        end

        io.write(string.format("a %s %d %d %s %.3f\n", name, v.from, v.to, direction, frameTimeS))
        animationFrames = animationFrames + (v.to - v.from) + 1
    end

    if animationFrames ~= #data.frames then
        app.alert("Warning: Missing animation tags on some frames")
    end

    io.close(atlasOutput)
    return atlasFilename
end

local function exportAtlas(requirePowerOfTwoSize, trimSprites, showUI, imFormat, pivotX, pivotY)
    local sprite = app.activeSprite

    exportSpriteSheet(sprite, trimSprites, showUI and not requirePowerOfTwoSize, imFormat, 0, 0)

    if requirePowerOfTwoSize then
        local size = spriteSheetSize(sprite)
        local w = nextPowerOfTwo(size.width)
        local h = nextPowerOfTwo(size.height)

        exportSpriteSheet(sprite, trimSprites, showUI, imFormat, w, h)
    end

    local atlasFilename = exportAtlasFile(sprite, imFormat, pivotX, pivotY)
end

local function onExport(dlg)
    exportAtlas(dlg.data.pow2, dlg.data.trimSprites, dlg.data.preview, dlg.data.imFormat,
                dlg.data.pivotX / 100.0, dlg.data.pivotY / 100.0)
    dlg:close()

    local prefsFile = io.open(app.fs.joinPath(app.fs.tempPath, "atlas_exporter_cache.json"), "w+")
    io.output(prefsFile)
    io.write(json.encode(dlg.data))
    io.close(prefsFile)
end

local function showExportDialog()
    local prefsFile = io.open(app.fs.joinPath(app.fs.tempPath, "atlas_exporter_cache.json"), "r")

    local prefs = {
        pow2        = true,
        trimSprites = true,
        preview     = false,
        imFormat    = "png",
        pivotX      = "0",
        pivotY      = "0"
    }

    if prefsFile ~= nil then
        prefs = json.decode(prefsFile:read("a"))
        io.close(prefsFile)
    end

    local dlg = Dialog("Export Atlas")
    local imFormatOptions = {"png", "tga", "bmp"}

    dlg:combobox{id = "imFormat", label = "Image Format",
                 options = prefs.imFormat, options = imFormatOptions}

    dlg:number{id = "pivotX", label = "Pivot", text = tostring(prefs.pivotX)}
    dlg:number{id = "pivotY", text = tostring(prefs.pivotY)}

    dlg:check{id = "pow2", text = "Power Of 2", selected = prefs.pow2}
    dlg:newrow()
    dlg:check{id = "trimSprites", text = "Trim Sprites", selected = prefs.trimSprites}
    dlg:newrow()
    dlg:check{id = "preview", text = "Preview", selected = prefs.Preview}

    dlg:newrow()
    dlg:separator()

    dlg:button{id = "ok", text = "&Export", focus = true, onclick = function() onExport(dlg) end}
    dlg:button{id = "cancel", text = "&Cancel", focus = false, onclick = function () dlg:close() end}

    dlg:show {wait = false}
end

if app.isUIAvailable then
    showExportDialog()
end