Media Server 12.11

# Configure Drawing with a Lua Script

The `Draw` transformation task draws regions on images or video frames. This section demonstrates how to customize the regions that are drawn by using a Lua script.

The Lua script that you write must define a function with the name `draw`. The function is passed each record from the input track. For example, the following function draws an ellipse on each record from the `ResultWithSource` track produced by face detection:

    function draw(record)
       drawEllipse(record.FaceResultAndImage.face.ellipse, 3, rgb(255,255,255))
    end

For information about the Lua functions that you can use to draw regions on images and video frames, refer to the Media Server Reference.

To configure drawing with a Lua script

1. Create a new configuration to send to Media Server with the `process` action, or open an existing configuration that you want to modify.

2. In the `[Session]` section, add a new task by setting the `EngineN` parameter. You can give the task any name, for example:

       [Session]
       Engine0=Ingest
       ...
       Engine3=Draw

3. Create a new configuration section to contain the task settings and set the following parameters:

   `Type` | The transformation engine to use. Set this parameter to `Draw`.
   `Input` | The name of the track that contains the images to draw on, with region data. The track must supply records that contain both an image and at least one region.
   `LuaScript` | The path of a Lua script to run to draw on the source images or video frames.

   For example:

       [Draw]
       Type=Draw
       Input=Demographics.ResultWithSource
       LuaScript=lua/drawDemographics.lua

4. Save and close the configuration file. Micro Focus recommends that you save your configuration files in the location specified by the `ConfigDirectory` parameter.

Example configuration to draw regions on encoded images using a Lua script

An example configuration file, `configurations/examples/Other/Draw_Faces.cfg`, is included in your Media Server installation.

The following example runs face detection and demographics analysis on a video file or stream. It encodes images of the detected faces, using a Lua script to outline male faces in orange and female faces in purple.

    [Session]
    Engine0=Ingest
    Engine1=FaceDetect
    Engine2=Demographics
    Engine3=Draw
    Engine4=Images

    [Ingest]
    Type=Video

    [FaceDetect]
    Type=FaceDetect
    NumParallel=6
    MinSize=10%

    [Demographics]
    Type=Demographics
    Input=FaceDetect.ResultWithSource
    NumParallel=2

    [Draw]
    Type=Draw
    Input=Demographics.ResultWithSource
    LuaScript=drawDemographics.lua

    [Images]
    Type=ImageEncoder
    ImageInput=Draw.Output
    OutputPath=./output/%session.token%/%record.starttime.iso8601%.png

The Lua script `drawDemographics.lua` is included below:

    function draw(record)
      local result = record.DemographicsResultAndImage

      if ('Male' == result.gender) then
        -- draw orange ellipse
        drawEllipse(result.face.ellipse, 5, rgb(255, 128, 0))

      elseif ('Female' == result.gender) then
        -- draw purple ellipse
        drawEllipse(result.face.ellipse, 5, rgb(64, 0, 128))

      else
        -- draw grey ellipse
        drawEllipse(result.face.ellipse, 5, rgb(128, 128, 128))

      end
    end

Example Lua script to process combined/nested records

To draw outlines around multiple types of region, for example both detected faces and recognized logos, you can combine multiple tracks using a combine ESP task. The output from the combine ESP task, and the input for the drawing task, is therefore a track where records contain other records. In this case, your Lua script must process the nested records. The following script demonstrates how to do this:

    function dispatchResult(record)
    	-- handle the single records here
    end

    function uncombine(record)
    	if (record.CombineOperationData) then
    		local i = 1
    		while (record.CombineOperationData.combinedRecords[i]) do
    			uncombine(record.CombineOperationData.combinedRecords[i])
    			i = i + 1
    		end
    		uncombine(record.CombineOperationData.record0)
    	else
    		dispatchResult(record)
    	end
    end

    function draw(record)
    	uncombine(record)
    end

© Copyright 2022 Micro Focus or one of its affiliates
Version 12.11 | Last updated February 2022

Send documentation feedback

Close

Send documentation feedback

To send feedback using your default email client, open an email window.

Otherwise, send your feedback and the information below to swpdl.idoldocsfeedback@microfocus.com.

We appreciate your feedback!

Product: IDOL Media Server 12.11

Topic Title: Configure Drawing with a Lua Script