document-scanner | An OpenCV based document scanner | Computer Vision library

I am trying to use openCV2 to automatically delineate the contours of churches and cathedrals from static maps.

In a nutshell, I am:

• scraping the building's coordinates from this Wikipedia page.
• creating a map centered on those coordinates using Folium, a Python library.
• saving the map as a jpg image.
• applying openCV2's findContours method to delineate the contours of the buildings.

I initially assumed that the cathedrals would be the largest building within a few hundred meters, so I sorted the contours by area following this PyImageSearch tutorial:

been trying to find the answer to why everybody converts an image to grayscale before processing?

For example, this website with instructions teaching people how to build a simple scanning program converts photo to greyscale first before passing commands to manipulate the image itself.

In the second example, this thread on stackoverflow shows a person also converts the image to grayscale before extracting text from his image.

Does this process make the image easier to manipulate? Or does it give better results when extracting text? If so, shouldn't a binary image give the best result in the case of extracting text?

So I am trying to follow guide on how to scan a document in https://www.pyimagesearch.com/2014/09/01/build-kick-ass-mobile-document-scanner-just-5-minutes/ exactly on the step 2 process where i am supposed to find the contour and draw it to the image, i got an "Assertion Failed" error on drawContour function

The guide did not have

screenCnt = None

so at first i got Error like screenCnt did not exist

after i add it, got Assertion Failed instead even though i used the same image as the guide and tried another image too

Given this image:

I'd like to make it such that it will rotate and stretch to fully fit in the bounding box with no whitespace on the outside of the largest rectangular box. It should also account for worse perspective case, like in the links I list later on.

Basically, while it is not noticeable, the rectangle is rotated a little bit, and I'd like to fix that distortion.

However, I got an error when attempting to retrieve the four points of the contour. I have made sure and utilized contour approximation to isolate and get only relevant looking contours and as you can see in the image it's successful, though I can't use perspective warp on it.

I've already tried the links here:

• How to straighten a rotated rectangle area of an image using opencv in python?
• https://www.pyimagesearch.com/2014/05/05/building-pokedex-python-opencv-perspective-warping-step-5-6/
• https://www.pyimagesearch.com/2014/09/01/build-kick-ass-mobile-document-scanner-just-5-minutes/

And followed them, with only minor modifications (like not downscaling the image and then upscaling it) and different input image.

There is a similar error encountered by a reader there in the comments, but the author just said to use contour approximation. I did that but I still receive the same error.

I have already retrieved the contour (which along with its bounding box, is the image illustrated earlier), and used this code to attempt persective warp:

Since approx. 72h I'm getting The job exceeded the maximum time limit for jobs, and has been terminated. on TravisCI which seems to be related requesting artifacts from mvnsearch.org, e.g. https://travis-ci.org/document-scanner/document-scanner-aggregator/builds/266942578. I assume it's a remote repository which I'm not using, but some of the project's dependencies are.

mavensearch.org seems to be unreachable or responding very slowly. I don't find any news on their operational status. It's odd that the issues isn't fixed within 72h, so I assume a long-time issue.

The only possible solution I could imagine would be to add the download and installation of a maven proxy to the Travis CI build script and proxy mavensearch.org in a Maven settings.xml file. Is there any way to avoid this?

It doesn't work to use the mirror element in ~/.m2/settings.xml because it references the repository id in referenced POMs which can be those of transitive dependencies and can change if snapshots are used and need to be checked and eventually adjusted after every version change.

I´m using the cordova-plugin-document-scanner plugin in my ionic 3 iOS App which allows me to take a photo with some additional features. Everything works fine and I get the fileURI in the success callback (file:///...).

After taking a Photo, I´m not able to update the DOM to show the image in my view home.html. I tried also to update a simple text (test), but it also do not work.

I´ve tried it with ngZone and also with ChangeDetectorRef. Both give me:

I'm regularily using Travis CI and noticed multiple issues with forked projects the last weeks when building on Travis which do not occur locally or on the Travis instance of the forked project. I made sure that I used the the same Maven version which imo is all that can be different from the Travis CI environment since both Maven and Java are portable across platforms. Travis runs Ubuntu 12.04 or 14.04 which I do as well (17.04).

In detail I experienced:

• The failure to retrieve a SNAPSHOT version which I could retrieve with the same Maven version locally after deleting ~/.m2/repository and moving ~/.m2/settings.xml aside (see Why fails Travis CI to retrieve a SNAPSHOT artifact when retrieval works locally? for details)
• [ERROR] Failed to execute goal org.jacoco:jacoco-maven-plugin:0.7.5.201505241946:check (default-check) on project commons-numbers-complex: Coverage checks have not been met. repeatedly which doesn't happen on their master branch (which I added to the aggregator of my project)

I'm not looking for solutions to the issues here, but to any explanation how this could make any sense in order to broaden my understanding of Travis and Maven in a cross-platform environment.

I'm suffering for a Could not find artifact org.apache.commons:commons-numbers-core:jar:1.0-SNAPSHOT Maven error on Travis CI which I can't explain because I ran the exact same build command locally after deleting ~/.m2/repository and moving ~/.m2/settings.xml to a backup location.

The error message is

So, I managed to detect document borders with opencv c++ code. Now, I need to crop that image and make it look decent.

Border detection looks good as you can see in this picture:

But now, when I try to crop it, it looks like this:

Now, this is the code im using: