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Best way to detect corners of a plaque and reference object (Java, Opencv, Android Studio)

first of all English is not my main language. So I'm sorry for any mistakes and also this is my first time using StackOverflow.
About my problem: I'm doing a research project at my college, where I have to create an app that is able to analyze an image of a plate and its reference object. And return the width and height of that plate using a picture taken with the app. I joined the project after it started so the app has to be made in android studio using java. The thing is, that my major is not in computer science. So maybe I don't have enough bag of knowledge, to know where to look and would like to know if you have tips on what I have to search for or anything that could help me .
Right now I'm doing the whole usual process of getting an object contour (threshold, blur, etc etc) and I have a really good threshold image.
I'm getting the contour of the plaque just fine but I'm having trouble with the reference object (the A4 sheet). I'm currently using Imgproc.approxPolyDP and the sheet proportion to ensure that the outline is that of the sheet and not some other outline of the plate, but if I can make it work for a specific photo it doesn't work for the real-time picture on the app.
So do you guys have any tips? Or should I talk to my teacher for him to make some concessions? I thought about making an interface where the user could select the right contours and then calculate the height and width values ​​but my teacher is very difficult to accept changes in the project.
Thanks in advance!

Blur A Circle In Java

I am writing a game in Java but have run in to an issue. I need to blur certain entitities within the game in order to create the right look. However, a lot of these objects are circular and so I am having issues blurring them properly.
Here is an example of the kind of thing I'm aiming for:
Currently, I'm using a box blur but just can't think of a way to achieve this sort of effect.
If somebody could give me a nudge in the direction I need to be looking that would be great.
Thanks.
Will

Flat infinate line?

I know that this is probably a very, very basic question but I'm very new. Basically I want to create a platform that my character can walk on. Almost like in the game "Flappy Bird" but, I want it to be a walkable platform. Is there any way I can create a "line" that stretches out infinitely. I've seen this, but it's for iOS and isn't a flat line. I've tried researching, but I haven't seen anything that appeals to what I'm looking to achieve. Any help would be great. As a heads up I'm using libGDX Also leading me to any tutorials for something similar would be equally appreciated.

There is a tutorial to create an exact copy of flappy bird
http://www.kilobolt.com/zombie-bird-tutorial-flappy-bird-remake.html
Could you modify this to create your walkable game?

Android traffic game developing

I'm developing simple traffic educational game like https://market.android.com/details?id=cz.allianz.krizovatky.android . When the player taps on car sprite, it started to move with other cars. If player made a mistake in choosing car, collision happens.
My question is: what is the best way for implementing such game (game engine or direct Canvas drawing)? I'm not game developer, it is my first game. Now, I'm trying to use Andengine, it looks great, but I have not enough experience :( The main problems are:
1) How to make car automatically move along specified path with smooth turns?
2) How generate random map with crossroads?
Please, help me choose the right way of development this game. If I should use game engine, how I can solve my problems with car moving and maps?

Depending on your experience with Java, I would say that tweaking your own Canvas would give you more control for more work, but a Game Engine would let you get started faster with more design/implementation restrictions.
You might also find better answers if you asked the same question over at : https://gamedev.stackexchange.com/

How to show only part of map on screen

I'm developer of game Space STG II for Android phones... and I want to add to this game new option. To do this I need to know how to do movable screen. I want to do a battle like in Heroes Might & Magic, but in mobile phone screen is small... I don't know how developers show only a part on screen of all things on map. I want to make a small map in corner which show which part of map is shown on screen.
I can't find it :/ I spend 2 days and I found only 2d tile moving, but I need smooth moves. Please help. I will give activation codes for Space STG II for help.

This question is rather vague, and so in return I can't reply with more than a vague answer. Adding this new feature to your game is very specific to how you wrote your game to begin with. If you used bad coding habits, it's going to be very difficult. From what I gather, you are trying to add a mini-map in the corner like many games have. If your model of the game and view are intertwined, you're going to have issues doing this. If you used a design pattern like Model-View-Controller http://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller it would be easier to add another "view" of your model and implement it as the minimap. Sorry for the vague answer, but I don't have much else to work with seeing as you have a specific question with not many details of how your game is written.

If you're writing OpenGL code, its extremely easy- just draw the scene and move the camera to look at whatever location you want. Scrolling means moving the camera and will be smooth. Note that a tile approach works fine with OpenGL
If you're using some other 2D API, it might not be that simple. You could try to look up algorithms yourself for how people implement scrolling in widgets (think- how do people make a listview?). You'll come up with something.
Edit: If you do accept this answer, I don't really want your activation codes. Thanks anyway.