Captioned screenshots for MPV

caption-screenshots.lua

require "mp"
local msg = require "mp.msg"
local utils = require "mp.utils"
-- Currently, I use webp quality=90
-- In the future: Use jxl quality=80
-- It might be nice to adjust the quality on a show-by-show basis

-- The format_json consults metatables to distinguish between empty arrays and lists
local json_object_metatable = { type = "MAP" }
function json_object(obj)
    setmetatable(obj, json_object_metatable) 
    return obj
end

function subtitle_screenshot(arg_format)
    local format = arg_format or "webp"

    local path = "/Users/cassie/Pictures/VideoScreenshots/"
    local base_filename = os.date("Screen Shot %Y-%m-%d at %H.%M.%S")
    local image_filename = path .. base_filename .. "." .. format
    local meta_filename = path .. "Meta/" .. base_filename .. ".json"

    local text, err = utils.format_json(json_object {
        version = 2,
        screenshot = image_filename,
        working_dir = mp.get_property("working-directory"),
        path = mp.get_property("path"),
        filename = mp.get_property("filename"),
        title = mp.get_property("media-title"),
        time = mp.get_property("time-pos/full"),
        subtitle = mp.get_property("sub-text"),
        subtitle_ass = mp.get_property("sub-text-ass"),
        -- v2 fields start here:
        secondary_subtitle = mp.get_property("secondary-sub-text"),
        stream_filename = mp.get_property("stream-open-filename"),
        audio_info = json_object {
            id = mp.get_property("current-tracks/audio/id"),
            title = mp.get_property("current-tracks/audio/title"),
            lang = mp.get_property("current-tracks/audio/lang"),
        },
        subtitle_info = json_object {
            id = mp.get_property("current-tracks/sub/id"),
            title = mp.get_property("current-tracks/sub/title"),
            lang = mp.get_property("current-tracks/sub/lang"),
        },
        secondary_subtitle_info = json_object {
            id = mp.get_property("current-tracks/sub2/id"),
            title = mp.get_property("current-tracks/sub2/title"),
            lang = mp.get_property("current-tracks/sub2/lang"),
        },
    })
    if text then
        local file = io.open(meta_filename, "w")
        file:write(text)
        file:close()
    else
        msg.error(err)
    end

    mp.command_native({"screenshot-to-file", image_filename})
end

mp.register_script_message("subtitle-screenshot", subtitle_screenshot)
--- mp.add_key_binding("s", "subtitle-screenshot", subtitle_screenshot)