openCV Troubleshooting (2) : error: ‘CV_LOAD_IMAGE_GRAYSCALE’ was not declared in this scope

This is due to different versions of openCV. Things got update to different names.

Didn't work:
image1=  cv::imread("test.bmp", CV_LOAD_IMAGE_GRAYSCALE);

Didn't work:
image1=  cv::imread("test.bmp", IMREAD_GRAYSCALE);

WORKED!!!!!
image1=  cv::imread("test.bmp", cv::ImreadModes::IMREAD_GRAYSCALE);


ref:
https://stackoverflow.com/questions/27424285/cv-load-image-grayscale-is-not-definedpy
https://stackoverflow.com/questions/22547416/open-cv-flags-dont-work

openCV Troubleshooting (1) : undefined reference to `cv::xxxx`

I am compiling openCV project with cmake and I am getting errors like:

test.cpp:(.text+0xc0): undefined reference to `cv::imread(std::string const&, int)'
test.cpp:(.text+0x11f): undefined reference to `cv::_OutputArray::_OutputArray(cv::Mat&)'
test.cpp:(.text+0x138): undefined reference to `cv::_InputArray::_InputArray(cv::Mat const&)'
test.cpp:(.text+0x158): undefined reference to `cv::cvtColor(cv::_InputArray const&, cv::_OutputArray const&, int, int)'
test.cpp:(.text+0x180): undefined reference to `cv::_InputArray::_InputArray(cv::Mat const&)'

The following compiling script won't cause the issue.

g++ -o test_1 test_1.cpp `pkg-config opencv --cflags --libs`

But to fix cmake compile, we need to add the following red line to CMakeList.txt.

cmake_minimum_required(VERSION 2.8)
project( DisplayImage )
find_package( OpenCV REQUIRED )
add_executable( DisplayImage DisplayImage.cpp )
target_link_libraries( DisplayImage ${OpenCV_LIBS} )

ref:

https://stackoverflow.com/questions/24337932/cannot-get-opencv-to-compile-because-of-undefined-references

https://stackoverflow.com/questions/16782432/linker-can-not-find-opencv-libraries-when-using-cmake
https://docs.opencv.org/2.4/doc/tutorials/introduction/linux_gcc_cmake/linux_gcc_cmake.html

Tinkering OpenWRT (18) : Toubleshooting MT7688AN Hardware

Problem (1) : Serial to TTL not working

     - Try use a laptop instead of a desktop. There might be compatibility issue between the motherboard and USB. Or just not enough power from USB on a desktop.

     - Try use a higher input than 3v3. Even 5v works.

ref:

https://blog.csdn.net/u012175418/article/details/52572672

openCV Troubleshooting (0): error: (-215:Assertion failed) !empty() in function 'detectMultiScale'

Trying to compile some example code (in Python) from the internet and got the following error:

Traceback (most recent call last):
  File "main.py", line 16, in <module>
    img = drawFaces(img)
  File "/home/boris/facedetect_example/example2/OpenCV-demo-master/Video-FaceDetection/face_detection.py", line 26, in drawFaces
    faces = detectFaces(img)
  File "/home/boris/facedetect_example/example2/OpenCV-demo-master/Video-FaceDetection/face_detection.py", line 18, in detectFaces
    faces = face_cascade.detectMultiScale(gray, 1.2, 5)
cv2.error: OpenCV(4.1.0) /home/boris/workspace/opencv-4.1.0/modules/objdetect/src/cascadedetect.cpp:1658: error: (-215:Assertion failed) !empty() in function 'detectMultiScale'

It turns out the cascade XML or file is missing or the path to it is incorrect or the create_capture path is incorrect. Of course, this is someone else's code.

Updated this line:

face_cascade = cv2.CascadeClassifier("/home/aaaaa/OpenCV-demo/opencv-data/haarcascades/haarcascade_frontalface_default.xml")

To 

face_cascade = cv2.CascadeClassifier("/usr/share/opencv/haarcascades/haarcascade_frontalface_default.xml")

Everything works now.

ref:

https://stackoverflow.com/questions/30508922/error-215-empty-in-function-detectmultiscale

KiCAD Tips -- 0 : How to Add a Footprint Library

I was still following the blinky example:
       https://contextualelectronics.com/topic/library-setup-and-part-association/

And it appears I don't have Housing SOIC footprint in my library. Here is how I solved it.

Step 1:
I couldn't find CvPCB anymore. But you can open it in EESchema, click


Step 2:
Preferences => Manage Footprint Libraries

Step 3:
Download your needed library from the following link:
      https://github.com/KiCad/kicad-library/wiki/Footprint-Libraries
I needed:
      https://github.com/kicad/Housings_SOIC.pretty

Step 4:
From the "Manage Footprint Libraries" Dialog, click "Browse Libraries..." and choose the downloaded file of the footprints.

Step 5:
You can notice the lists update in 5 seconds.

KiCAD Tips -- 0 : How to Add a Library

The following tutorial is awesome but like may other materials online, it is in KiCAD 4.0.
                      https://contextualelectronics.com/topic/creating-schematic-symbols/

The steps to create a new library and switch from the official library directory to the project directory to edit my own library are totally gone in KiCAD 5.0.2.

But eventually, I figured it out and it is actually easier.

Step 1: Click   to open the Symbol Library Editor.

Step 2: From the search tree on the left side, input device and select C. As described in the above tutorial, we are going to create our own library based on existing library. This capacitor is just a holder.

We can see from the above picture on the top bar, it is still pointing to the CAD's own library. But we want to customize it in our own project directory. 

Step 3: 

Click  to create a new library

Step 4: save the new library in your project

and 

Step 5: 

Now you can see it is added to your library tree.

But check out the top bar, it is still saying /usr/share/kicad/library...

Step 6: Right click myBlink => new symbol

Name your new component in this library:

Step 7:

Now the working directory has been set to your project and you can edit your component in your own library.

NO_PUBKEY Issue

Hit:21 http://ppa.launchpad.net/webupd8team/sublime-text-3/ubuntu xenial InRelease
Fetched 1,490 B in 1s (1,302 B/s)                 
Reading package lists... Done
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://dl.winehq.org/wine-builds/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 76F1A20FF987672F
W: GPG error: http://download.opensuse.org/repositories/home:/emby/xUbuntu_16.04  Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 0A506F712A7D8A28
W: The repository 'http://download.opensuse.org/repositories/home:/emby/xUbuntu_16.04  Release' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: Failed to fetch https://dl.winehq.org/wine-builds/ubuntu/dists/xenial/InRelease  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 76F1A20FF987672F
W: Some index files failed to download. They have been ignored, or old ones used instead.

wget -nc https://dl.winehq.org/wine-builds/winehq.key && sudo apt-key add winehq.key && sudo apt update

boris@boris-home:~$ wget -nc https://dl.winehq.org/wine-builds/winehq.key && sudo apt-key add winehq.key && sudo apt update
--2019-01-15 00:43:38--  https://dl.winehq.org/wine-builds/winehq.key
Resolving dl.winehq.org (dl.winehq.org)... 151.101.126.217
Connecting to dl.winehq.org (dl.winehq.org)|151.101.126.217|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 3220 (3.1K) [application/pgp-keys]
Saving to: ‘winehq.key’

winehq.key          100%[===================>]   3.14K  --.-KB/s    in 0s      

2019-01-15 00:43:38 (77.1 MB/s) - ‘winehq.key’ saved [3220/3220]

OK
Ign:1 http://linux.dropbox.com/ubuntu wily InRelease
Ign:2 http://dl.google.com/linux/chrome/deb stable InRelease                   
Hit:3 http://linux.dropbox.com/ubuntu wily Release                             
Hit:6 http://archive.canonical.com/ubuntu xenial InRelease                     
Hit:7 http://repository.spotify.com stable InRelease                           
Ign:8 http://download.opensuse.org/repositories/home:/emby/xUbuntu_16.04  InRelease
Hit:9 http://dl.google.com/linux/chrome/deb stable Release                     
Get:10 https://dl.winehq.org/wine-builds/ubuntu xenial/main amd64 Packages [145 kB]
Hit:11 http://ca.archive.ubuntu.com/ubuntu xenial InRelease                    
Hit:12 http://ppa.launchpad.net/fpoussin/ppa/ubuntu xenial InRelease           
Hit:13 http://download.opensuse.org/repositories/home:/emby/xUbuntu_16.04  Release
Get:14 https://dl.winehq.org/wine-builds/ubuntu xenial/main i386 Packages [151 kB]
Get:15 http://ca.archive.ubuntu.com/ubuntu xenial-updates InRelease [109 kB]   
Get:16 http://download.opensuse.org/repositories/home:/emby/xUbuntu_16.04  Release.gpg [481 B]
Hit:18 http://ppa.launchpad.net/gezakovacs/ppa/ubuntu xenial InRelease         
Ign:16 http://download.opensuse.org/repositories/home:/emby/xUbuntu_16.04  Release.gpg
Hit:19 http://ppa.launchpad.net/mosquitto-dev/mosquitto-ppa/ubuntu xenial InRelease
Get:20 http://ca.archive.ubuntu.com/ubuntu xenial-backports InRelease [107 kB] 
Hit:21 http://ppa.launchpad.net/webupd8team/sublime-text-3/ubuntu xenial InRelease
Hit:22 http://archive.ubuntukylin.com:10006/ubuntukylin xenial InRelease
Reading package lists... Done 
W: GPG error: http://download.opensuse.org/repositories/home:/emby/xUbuntu_16.04  Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 0A506F712A7D8A28
E: The repository 'http://download.opensuse.org/repositories/home:/emby/xUbuntu_16.04  Release' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

boris@boris-home:~$ 


You can see the key issue from WinHQ is gone now.

###########################################################

$ sudo -i 

 # apt-get clean 

 # cd /var/lib/apt 

 # mv lists lists.old 

 # mkdir -p lists/partial 

 # apt-get clean 

 # apt-get update

sudo sed -i '/opensuse/ s/^/#/' /etc/apt/sources.list.d/*.list

Now the key issue from opensuse should also be gone.


ref:
https://askubuntu.com/questions/1103320/the-following-signatures-couldnt-be-verified-because-the-public-key-is-not-avai
https://ubuntuforums.org/showthread.php?t=1869890&page=3
https://askubuntu.com/questions/522114/cant-get-rid-of-gpg-error-http-download-opensuse-org

Troubleshooting when Setting up Github Page

At the step of setting up Ruby locally for testing, I got this:

Fetching gem metadata from https://rubygems.org/..............
Fetching gem metadata from https://rubygems.org/..
Resolving dependencies.....
Fetching concurrent-ruby 1.1.4
Installing concurrent-ruby 1.1.4
Fetching i18n 0.9.5
Installing i18n 0.9.5
Fetching minitest 5.11.3
Installing minitest 5.11.3
Fetching thread_safe 0.3.6
Installing thread_safe 0.3.6
Fetching tzinfo 1.2.5
Installing tzinfo 1.2.5
Fetching activesupport 4.2.10
Installing activesupport 4.2.10
Fetching public_suffix 2.0.5
Installing public_suffix 2.0.5
Fetching addressable 2.5.2
Installing addressable 2.5.2
Using bundler 1.17.3
Fetching coffee-script-source 1.11.1
Installing coffee-script-source 1.11.1
Fetching execjs 2.7.0
Installing execjs 2.7.0
Fetching coffee-script 2.4.1
Installing coffee-script 2.4.1
Fetching colorator 1.1.0
Installing colorator 1.1.0
Fetching ruby-enum 0.7.2
Installing ruby-enum 0.7.2
Fetching commonmarker 0.17.13
Installing commonmarker 0.17.13 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

current directory:
/home/boris/workspace/my_Github_Website/codemonkeyboris.github.io/vendor/bundle/ruby/2.5.0/gems/commonmarker-0.17.13/ext/commonmarker
/usr/bin/ruby2.5 -r ./siteconf20181231-18337-kelz2o.rb extconf.rb
mkmf.rb can't find header files for ruby at /usr/lib/ruby/include/ruby.h

extconf failed, exit code 1

Gem files will remain installed in
/home/boris/workspace/my_Github_Website/codemonkeyboris.github.io/vendor/bundle/ruby/2.5.0/gems/commonmarker-0.17.13 for inspection.
Results logged to
/home/boris/workspace/my_Github_Website/codemonkeyboris.github.io/vendor/bundle/ruby/2.5.0/extensions/x86_64-linux/2.5.0/commonmarker-0.17.13/gem_make.out

An error occurred while installing commonmarker (0.17.13), and Bundler cannot continue.
Make sure that `gem install commonmarker -v '0.17.13' --source 'https://rubygems.org/'` succeeds before bundling.

In Gemfile:
  github-pages was resolved to 193, which depends on
    jekyll-commonmark-ghpages was resolved to 0.1.5, which depends on
      jekyll-commonmark was resolved to 1.2.0, which depends on
        commonmarker

#####################################################

Solution:

$sudo apt-get install ruby-all-dev

$bundle install --path vendor/bundle

ref:

https://help.github.com/articles/setting-up-your-github-pages-site-locally-with-jekyll/

https://github.com/github/pages-gem/issues/133