How does it achieve OCR?

这是我写的一个插件。晚些时间我会将它发布到网络上。你在哪看到的这个演示图片？ This is a plugin I wrote. I will post it to the web later. Where did you see this demo picture?

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I'm challenged I can not read the  menu items used in you animated Gif.  However you did post in the scripting forum. So I imagine you used a Script.  If the script is saved into a JSXBIN you can not read what it is doing.  It may be doing something like I did in my potrace script.  Where I executed a windows application to trace a grayscale image.  Where the Script pooled to see if the application output was created,  once it was the script use it to define a  custom shape and add that shape on top of the document being processed.

In this case the script may have executed some OCR application then uset its output to create text layers.