Using Tesseract OCR in Elixir/Phoenix

Lately, I am exploring the use of OCR in Expendere (my expense tracking application) and came across Tesseract OCR.

At the time of writing this blog post, there is no native binding of Tesseract OCR in Elixir. However, there are two Elixir wrapper available on GitHub:

• tesseract-ocr-elixir
• tesseract-elixir

Both wrapper use System.cmd/3 to invoke the tesseract command line interface and return the results of the executed command.

Seeing there are wrappers available out there, I quickly grab one and scaffold a Phoenix application to test it out.

Code

In this code example, I will be using wrapper from tesseract-ocr-elixir.

In mix.exs, add tesseract-ocr-elixir as dependency:

def deps do
  [
    ...,
    {:tesseract_ocr, "~> 0.1.0"}
  ]
end

In page_controller.ex:

defmodule OcrWeb.PageController do use OcrWeb, :controller

  def index(conn, _params) do
    render(conn, "index.html")
  end

  def create(conn, %{"upload" => %Plug.Upload{} = upload}) do
    result = TesseractOcr.read(upload.path)
    render(conn, "show.html", result: result)
  end
end

In router.ex, add this under scope "/":

get "/", PageController, :index
post "/upload", PageController, :create

In templates/page/index.html.eex:

<%= form_for @conn, Routes.page_path(@conn, :create),
                    [multipart: true], fn f-> %>
    <%= file_input f, :upload, class: "form-control" %>
    <%= submit "Upload", class: "btn btn-primary" %>
<% end %>

In templates/page/show.html.eex:

<h1>Result:</h1>

<%= @result %>

Demo

Voila, a simple OCR application is done. The demo application is available at GitHub.