How to find contours in image using evision and nx?

Learning Questions & Discussions Homework Help
21

You should provide the error stack trace…

22

As of 0.1.12, the precompiled binaries for Linux are using GTK2 as the backend. So please install the corresponding libraries. The instruction that you need to install the library should be shown in the error message. For Debian/Ubuntu:

sudo apt-get install libgtk2.0-dev

Meanwhile, it is also possible to compile everything from source so that OpenCV will auto-detect and support (if they have the corresponding implementation) the backend you have on your system.

The instruction to compile everything from source is given in the very first line of the README.md file, and I copied it here for you:

If you find the precompiled binaries do not suit your needs (e.g., perhaps you need OpenCV to be compiled with FFmpeg to handle more video formats.), it’s possible to override the behaviour by setting the environment variable EVISION_PREFER_PRECOMPILED to false, and then please delete _build/${MIX_ENV}/lib/evision and recompile evision

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23

Show function gives this error ??

** (ArgumentError) argument error
    (evision 0.1.4-dev) :evision_nif.imshow([winname: "image", mat: {:ok, #Reference<0.4008954437.2381709314.47653>}])
    (evision 0.1.4-dev) lib/evision_highgui.ex:28: Evision.HighGui.imshow!/2
    (task1b_number_detection 0.1.0) lib/task1b_number_detection.ex:22: Task1bNumberDetection.show/1

This is my dependencies
{:evision, “~> 0.1.0-dev”, github: “cocoa-xu/evision”, branch: “main”},
{:nx, “~> 0.2”},
{:tesseract_ocr, “~> 0.1.5”}

24

Hi, some dependencies are outdated, please use the following ones

{:evision, "~> 0.1.14"},
{:nx, "~> 0.3"},
{:tesseract_ocr, "~> 0.1.5"}

Also, if you are using it on Linux, please note that the precompiled evision binary is not compiled with GTK. Please set the environment variable EVISION_PREFER_PRECOMPILED to false. Or, you can use the precompiled version and Evision.Wx.imshow/2 (instead of Evision.HighGui.imshow/2) if Erlang on your system is compiled with wxWidgets.

25

I have ran “export EVISION_PREFER_PRECOMPILED=false” to set environment variable and deleted _bulid file for mix compile but every time I get this error

== Compilation error in file lib/smartcell/ml_traindata.ex ==
** (CompileError) lib/smartcell/ml_traindata.ex:3: module Kino.JS is not loaded and could not be found. This may be happening because the module you are trying to load directly or indirectly depends on the current module
(elixir 1.13.4) expanding macro: Kernel.use/2
lib/smartcell/ml_traindata.ex:3: Evision.SmartCell.ML.TrainData (module)
(elixir 1.13.4) expanding macro: Kernel.if/2
lib/smartcell/ml_traindata.ex:2: Evision.SmartCell.ML.TrainData (module)

26

Sorry but I need more information because the problem you described cannot be reproduced locally or on CI.

Have you tried mix deps.update kino? Or could you please copy and paste your mix.exs file so that I can try to reproduce the issue?

27

#mix.exs file

defmodule Task1bNumberDetection.MixProject do
  use Mix.Project

  def project do
    [
      app: :task1b_number_detection,
      version: "0.1.0",
      start_permanent: Mix.env() == :prod,
      deps: deps()
    ]
  end

  def application do
    [
      extra_applications: [:logger]
    ]
  end

  defp deps do
    [
      {:evision, "~> 0.1.14"},
      {:nx, "~> 0.3.0"},
      {:tesseract_ocr, "~> 0.1.5"}
    ]
  end
end
28

evision lists kino as optional: true in its mix.exs, which means it can work with Kino but does not require it. If you’re using Kino, you’ll want to list it explicitly in your mix.exs.

However, something peculiar is going on: the line that’s failing for you is protected by a guard that should keep it from running:

If Kino isn’t loaded, it shouldn’t even try to run line 3… :thinking:

29

Got it, and fix is on the way. I’ll let you know 0.1.15 is released.

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30

Yeah, that’s also what I thought… maybe I need to read the implementation of use in Elixir.

But anyway, I’ll adhere to elixir’s behaviour and make :kino a required dependency for now.

31

v0.1.15 is available on hex now. :slight_smile: @gaurav136

32

Thank You :smiley: it’s now working as expected

33

The detailed reason and explanation can be found on my blog: Conditional compilation with “if” and “use” in Elixir

I’m too sleepy right now I’ll probably format it to markdown later and then post it on elixirforum :sleeping:

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