Converting Java BufferedImage to OpenCV Mat and vice versa

The code below allows us to convert BufferedImage to Mat (in OpenCV) and vice versa.

This becomes handy when getting images from network or certain other sources:

REST Application in Java

Below are the basic steps to create a working REST API Application in java, using Eclipse.
The demo shows just a “To Uppercase String” application

Steps:

  • In Eclipse, create a new Project(Dynamic Web Project)
  • Create the new Project and give it a suitable name.
  • after project creation, right click on the project, and select Configure-> Convert to Maven Project
  • After process completion, a pom.xml would be made available.
  • Add the dependencies from the pom.xml that I have presented below.
  • Create new Class as sample shown below and create methods that you need to expose.
  • Add business logic as per need.
  • Add Annotations to the class as shown below
  • In the Web Content folder, modify the web.xml as shown in the sample web.xml

The basic mode is complete. Now just configure your local web server and deploy your application to the web server.

Use any REST Client like Postman(Chrome Plugin) to test the app.

Code Samples

HackerEarth: Battle Of Bots #5: Reversi

Problem:

Reversi is a two player board game which is played on a 10 x 10 grid of cells. Each player has an allocated color, Black ( First Player ) or White ( Second Player ) being conventional. Players take turns placing a stone of their color on a single cell. A player must place a stone on the board, in such a position that there exists at least one straight (horizontal, vertical, or diagonal) occupied line between the new stone and another stone of same color, with one or more contiguous other color stone between them.

During a game, any stone of the opponent’s color that are in a straight line and bounded by the stone just placed and another stone of the current player’s color are turned over to the current player’s color. The game will end when the board is completely filled or both the players don’t have any move left. At the end of the game the player with majority of stone will win.

We will play it on an 10 x 10 grid. The top left of the grid is [0,0] and the bottom right is [9,9]. The rule is that a cell[i,j] is connected to any of top, left, right, or bottom cell.

Input:
The input will be a 10 x 10 matrix consisting only of 0,1,2 or 3. Then another line will follow which will contain a number – 1 or 2 which is your player id.

In the given matrix, top-left is [0,0] and bottom-right is [9,9].

In cell[row,column], row increases from top to bottom and column increases from left to right.

The cell marked 0 means it doesn’t contain any stones. The cell marked 1 means it contains first player’s stone which is Black in color. The cell marked 2 means it contains second player’s stone which is white in color. The cell marked 3 means it is a valid place for player whose turn it is.

Output:
Print the coordinates of the cell separated by space, where you want to play your move. You must take care that you don’t print invalid coordinates. For example, [1] might be a valid coordinate in the game play if cell[i,j]=3, but [10] will never be. Also if you play an invalid move or your code exceeds the time/memory limit while determining the move, you lose the game.

Starting state
The starting state of the game is the state of the board before the game starts.

0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 2 1 0 0 0 0
0 0 0 0 1 2 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0

First Input
This is the input give to the first player at the start of the game.

0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 3 0 0 0 0 0
0 0 0 3 2 1 0 0 0 0
0 0 0 0 1 2 3 0 0 0
0 0 0 0 0 3 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
1

Scoring
The scores are calculated by running tournament of all submissions. Your latest submission will be taken into tournament. Scores are assigned according to the Glicko-2 rating system. For more information and questions, see Bot problem judge.

SAMPLE INPUT

0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 3 0 0 0 0 0
0 0 0 3 2 1 3 0 0 0
0 0 0 0 2 2 0 0 0 0
0 0 0 3 1 1 2 3 0 0
0 0 0 1 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
1
SAMPLE OUTPUT
4 3

Explanation

This is player 1’s turn, and the player puts his/her stone in cell[4,3].
After his/her move the state of game becomes:

0 0 0 0 0 0 0 0 0 0  
0 0 0 0 0 0 0 0 0 0  
0 0 0 0 0 0 0 0 0 0  
0 0 0 3 0 3 0 0 0 0  
0 0 0 1 1 1 0 0 0 0  
0 0 0 3 1 2 0 0 0 0  
0 0 0 3 1 1 2 0 0 0  
0 0 0 1 0 3 0 0 0 0  
0 0 3 0 0 0 0 0 0 0  
0 0 0 0 0 0 0 0 0 0  

This state will be fed as input to program of player 2.


Time Limit:1.0 sec(s) for each input file.
Memory Limit: 256 MB
Source Limit: 1024 KB
Marking Scheme:Marks are awarded if any testcase passes.
Allowed Languages:C, CPP, CLOJURE, CSHARP, D, ERLANG, FSHARP, GO, GROOVY, HASKELL, JAVA, JAVA8, JAVASCRIPT, JAVASCRIPT_NODE, LISP, LISP_SBCL, LUA, OBJECTIVEC, OCAML, OCTAVE, PASCAL, PERL, PHP, PYTHON, PYTHON3, R, RACKET, RUBY, RUST, SCALA, SWIFT, VB

My Solution:

How to determine which jar a class is loaded from?

When the method that contains this sniplet is called, it will print out something like:

file://path/to/deployment/lib/detected.jar

Will the codeSource be null? The answer is yes. When a jar file is loaded by the system class loader, it’s codeSource will be null. What jars will be loaded by the system class loader? the rule of thumb is that all the jars in the class path (not the ones you package in your application) will be loaded by the system class loader. Obviously the above code can’t used to find out which jar a class is loaded from, if the jar is loaded by the system class loader. You can use the “verbose” java command line argument when you start the application:

java -verbose app

it will print out every class in each jar the system class loader loads, ie:

[Opened C:\dev\bea\JDK160~1\jre\lib\rt.jar]
[Loaded java.lang.Object from C:\dev\bea\JDK160~1\jre\lib\rt.jar]
[Loaded java.io.Serializable from C:\dev\bea\JDK160~1\jre\lib\rt.jar]
[Loaded java.lang.Comparable from C:\dev\bea\JDK160~1\jre\lib\rt.jar]
[Loaded java.lang.CharSequence from C:\dev\bea\JDK160~1\jre\lib\rt.jar]
[Loaded java.lang.String from C:\dev\bea\JDK160~1\jre\lib\rt.jar]
[Loaded java.lang.reflect.GenericDeclaration from C:\dev\bea\JDK160~1\jre\lib\rt.jar]

Source

Apache Solr vs Elasticsearch: The Feature Smackdown

API

Feature Solr 5.3.0 ElasticSearch 2.0
Format XML,CSV,JSON JSON
HTTP REST API
Binary API SolrJ TransportClient, Thrift (through a plugin)
JMX support ES specific stats are exposed through the REST API
Official client libraries Java Java, Groovy, PHP, Ruby, Perl, Python, .NET, JavascriptOfficial list of clients
Community client libraries PHP, Ruby, Perl, Scala, Python, .NET, Javascript, Go, Erlang, Clojure Clojure, Cold Fusion, Erlang, Go, Groovy, Haskell, Java, JavaScript, .NET, OCaml, Perl, PHP, Python, R, Ruby, Scala, Smalltalk, Vert.x Complete list
3rd-party product integration (open-source) Drupal, Magento, Django, ColdFusion, WordPress, OpenCMS, Plone, Typo3, ez Publish, Symfony2, Riak (via Yokozuna) Drupal, Django, Symfony2, WordPress, CouchBase
3rd-party product integration (commercial) DataStax Enterprise Search, Cloudera Search, Hortonworks Data Platform, MapR SearchBlox, Hortonworks Data Platform, MapR etcComplete list
Output JSON, XML, PHP, Python, Ruby, CSV, Velocity, XSLT, native Java JSON, XML/HTML (via plugin)

Infrastructure

Feature Solr 5.3.0 ElasticSearch 2.0
Master-slave replication Only in non-SolrCloud. In SolrCloud, behaves identically to ES. Not an issue because shards are replicated across nodes.
Integrated snapshot and restore Filesystem Filesystem, AWS Cloud Plugin for S3 repositories, HDFS Plugin for Hadoop environments, Azure Cloud Plugin for Azure storage repositories

Indexing

Feature Solr 5.3.0 ElasticSearch 2.0
Data Import DataImportHandler – JDBC, CSV, XML, Tika, URL, Flat File [DEPRECATED in 2.x] Rivers modules – ActiveMQ, Amazon SQS, CouchDB, Dropbox, DynamoDB, FileSystem, Git, GitHub, Hazelcast, JDBC, JMS, Kafka, LDAP, MongoDB, neo4j, OAI, RabbitMQ, Redis, RSS, Sofa, Solr, St9, Subversion, Twitter, Wikipedia
ID field for updates and deduplication
DocValues
Partial Doc Updates with stored fields with _source field
Custom Analyzers and Tokenizers
Per-field analyzer chain
Per-doc/query analyzer chain
Synonyms Supports Solr and Wordnet synonym format
Multiple indexes
Near-Realtime Search/Indexing
Complex documents
Schemaless 4.4+
Multiple document types per schema One set of fields per schema, one schema per core
Online schema changes Schemaless mode or via dynamic fields. Only backward-compatible changes.
Apache Tika integration
Dynamic fields
Field copying via multi-fields
Hash-based deduplication Murmur plugin or ER plugin

Searching

Feature Solr 5.3.0 ElasticSearch 2.0
Lucene Query parsing
Structured Query DSL Need to programmatically create queries if going beyond Lucene query syntax.
Span queries via SOLR-2703
Spatial/geo search
Multi-point spatial search
Faceting Top N term accuracy can be controlled with shard_size
Advanced Faceting New JSON faceting API blog post
Geo-distance Faceting
Pivot Facets
More Like This
Boosting by functions
Boosting using scripting languages
Push Queries JIRA issue Percolation. Distributed percolation supported in 1.0
Field collapsing/Results grouping
Spellcheck Suggest API
Autocomplete
Query elevation workaround
Joins Joined index has to be single-shard and replicated across all nodes. via has_children and top_children queries
Resultset Scrolling New to 4.7.0 via scan search type
Filter queries also supports filtering by native scripts
Filter execution order local params and cache property
Alternative QueryParsers DisMax, eDisMax query_string, dis_max, match, multi_match etc
Negative boosting but awkward. Involves positively boosting the inverse set of negatively-boosted documents.
Search across multiple indexes it can search across multiple compatible collections
Result highlighting
Custom Similarity
Searcher warming on index reload Warmers API
Term Vectors API

Customizability

Feature Solr 5.3.0 ElasticSearch 2.0
Pluggable API endpoints
Pluggable search workflow via SearchComponents
Pluggable update workflow
Pluggable Analyzers/Tokenizers
Pluggable Field Types
Pluggable Function queries
Pluggable scoring scripts
Pluggable hashing
Pluggable webapps site plugin
Automated plugin installation Installable from GitHub, maven, sonatype or elasticsearch.org

 

Full article

CodeEval: Penultimate Word

Challenge Description:

Write a program which finds the next-to-last word in a string.

Input Sample:

Your program should accept as its first argument a path to a filename. Input example is the following

some line with text
another line

Each line has more than one word.

Output Sample:

Print the next-to-last word in the following way.

with
another

Solution:

 

CodeEval: Shortest Repetition

Challenge Description:

Write a program to determine the shortest repetition in a string.
A string is said to have period p if it can be formed by concatenating one or more repetitions of another string of length p. For example, the string “xyzxyzxyzxyz” has period 3, since it is formed by 4 repetitions of the string “xyz”. It also has periods 6 (two repetitions of “xyzxyz”) and 12 (one repetition of “xyzxyzxyzxyz”).

Input Sample:

Your program should accept as its first argument a path to a filename. Each line will contain a string of up to 80 non-blank characters. E.g.

abcabcabcabc
bcbcbcbcbcbcbcbcbcbcbcbcbcbc
dddddddddddddddddddd
adcdefg

Output Sample:

Print out the smallest period of the input string. E.g.

3
2
1
7

Solution:

 

CodeEval: PASS TRIANGLE

CHALLENGE DESCRIPTION:

By starting at the top of the triangle and moving to adjacent numbers on the row below, the maximum total from top to bottom is 27.

   5
  9 6
 4 6 8
0 7 1 5

5 + 9 + 6 + 7 = 27

INPUT SAMPLE:

Your program should accept as its first argument a path to a filename. Input example is the following:

5
9 6
4 6 8
0 7 1 5

You make also check full input file which will be used for your code evaluation.

OUTPUT SAMPLE:

The correct output is the maximum sum for the triangle. So for the given example the correct answer would be 27

Solution

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