RxLowpoly

An Android library to bring your ordinary photos to life with an awesome crystallized effect.

Introduction
Lowpoly Samples
Installation
Library Details
Usage Examples
Critical Analysis
Sample App
How to Contribute
About the Author
License

Introduction

RxLowpoly serves as an improvement over XLowPoly by

fixing out of memory crashes by scaling down the image in a loss-less manner before processing.
providing better quality results by using 4000 as the point count by default which provides a good trade-off between speed and time.
the higher point count leads to a longer execution period, but it is significantly reduced by scaling down the image before processing.
provides wider choice of input sources like Bitmap, File, Uri or Drawable resource.
natively using RxJava for background processing thereby reducing boilerplate code on the developer's end.

Lowpoly Samples

Original Image | Lowpoly Image -------------- | ------------- <img src="https://i.imgur.com/iCddK29.jpg" alt="Original" width=400 height=250> | <img src="https://i.imgur.com/Z4zOgqH.jpg" alt="Lowpoly" width=400 height=250> <img src="https://i.imgur.com/C5wzAqx.jpg" alt="Original" width=400 height=250> | <img src="https://i.imgur.com/mLjjrax.jpg" alt="Lowpoly" width=400 height=250> <img src="https://i.imgur.com/Ho86fyo.jpg" alt="Original" width=400 height=250> | <img src="https://i.imgur.com/pm8MV8m.png" alt="Lowpoly" width=400 height=250> <img src="https://i.imgur.com/D4DP8fu.jpg" alt="Original" width=400 height=250> | <img src="https://i.imgur.com/1zgjCyE.jpg" alt="Lowpoly" width=400 height=250>

Installation

Add the dependency in your app module's build.gradle file

dependencies {
	...
        implementation "com.zebrostudio.rxlowpoly:rxlowpoly:{latest_version}"
}

That's it!

Library Details

RxLowpoly uses JNI with 64 bit support to meet google specified requirement for all apps to be 64 bit enabled by August 2019.
Use of JNI enables much faster execution than other similar libraries.
Use of Sobel Operator for edge detection.
Use of Delaunay Triangulation on the result from the sobel operator to construct the final crystallized lowpoly effect on the image.

JNI

RxLowpoly uses the <a href="https://developer.android.com/training/articles/perf-jni">Java Native Interface</a> to run native code written in C which provides much faster processing for edge detection using the Sobel Operator and then implementing the Delaunay Triangulation algorithm.

Sobel Operator

The <a href="http://homepages.inf.ed.ac.uk/rbf/HIPR2/sobel.htm">Sobel Edge Detector</a> is a gradient based edge detection algorithm which provides us with separate planes on which the Delaunay Triangulation can be applied.

Delaunay Triangulation

We take a set P of discrete points on an image plane and apply <a href="https://en.wikipedia.org/wiki/Delaunay_triangulation">Delaunay Triangulation</a> DT(P) to produce triangles connecting 3 points at a time such that no point in **P **is inside the circum-circle of any triangle in DT(P). These separate triangles taken together in-turn provide us with the image having a crystallized effect.

Which leads to the resultant crystallized image as :-

Usage Examples

Asynchronous call

The most simple use case is :-
```
  RxLowpoly.with(context)
      .input(bitmap) 
      .generateAsync()
```
Along with Bitmaps we can also use Drawables or Files or Uri as input.

When we need to downscale the image :-

 RxLowpoly.with(context)
     .input(bitmap)
     .overrideScaling(downScalingFactor)
     .generateAsync()

When we need to set a maximum width for the image :-

 RxLowpoly.with(context)
     .input(bitmap)
     .overrideScaling(maxWidth)
     .generateAsync()

We can also set a quality for the lowpoly image :-

 RxLowpoly.with(context)
     .input(inputUri)
     .overrideScaling(downScalingFactor)
     .quality(Quality.HIGH)
     .generateAsync()

VERY_HIGH, MEDIUM, LOW and VERY_LOW are also available as Quality configurations

To save the lowpoly image to a file :-

 RxLowpoly.with(context)
     .input(inputUri)
     .overrideScaling(downScalingFactor)
     .quality(Quality.HIGH)
     .output(outputFile) // An Uri of a File is also supported as an output destination
     .generateAsync()

All asynchronous operation is done on the IO scheduler.

Synchronous call

Replacing generateAsync() with generate() in each of the Asynchronous call examples leads to a synchronous call with a lowpoly Bitmap as a result.

A Bitmap of the generated lowpoly image is always returned irrespective of synchronous or asynchronous calls and whether an output File or Uri is supplied using the output method.

Note : A full implementation can be found in the <a href="https://github.com/abhriyaroy/RxLowpoly/tree/master/app">app module</a> of this repository or in the open sourced <a href="https://github.com/abhriyaroy/WallR2.0">WallR</a> app.

Critical Analysis

The following tests have been performed on a Xiaomi Redmi Note 5 Pro with 6 gb Ram.

Original Image | Lowpoly Image | Input Source | Quality | Execution Time (ms) ----------------------------------- | ------------- | ------------ | ------- | ------ <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/AR10HF3.png" width=360 height=200> | Bitmap | Very High | 15813 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/XDd5nti.png" width=360 height=200> | Drawable | Very High | 16275 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/MVHzIbs.png" width=360 height=200> | File | Very High | 15987 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/cajVv2j.png" width=360 height=200> | Uri | Very High | 15931 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/OMSV6Ks.png" width=360 height=200> | Bitmap | High | 4547 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/9sThhqj.png" width=360 height=200> | Drawable | High | 5088 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/mlSfBBD.png" width=360 height=200> | File | High | 4734 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/HvBU1en.png" width=360 height=200> | Uri | High | 4612 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/KDMzSwy.png" width=360 height=200> | Bitmap | Medium | 1113 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/wz1aAhd.png" width=360 height=200> | Drawable | Medium | 1672 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/20YfeVF.png" width=360 height=200> | File | Medium | 1297 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/7tYMYcZ.png" width=360 height=200> | Uri | Medium | 1152 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/TeYASKY.png" width=360 height=200> | Bitmap | Low | 918 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/BXUCBJB.png" width=360 height=200> | Drawable | Low | 1496 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/FXmsHa5.png" width=360 height=200> | File | Low | 1091 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/muLCMQX.png" width=360 height=200> | Uri | Low | 996 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/R3p7FOn.png" width=360 height=200> | Bitmap | Very Low | 850 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/lei9Yzx.png" width=360 height=200> | Drawable | Very Low | 1024 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/RyvOjuF.png" width=360 height=200> | File | Very Low | 923 <img src="https://i.imgur.com/iCddK29.jpg" width=360 height=200> | <img src="https://i.imgur.com/cKZgHvM.png" width=360 height=200> | Uri | Very Low | 876

Thus it is evident that when quality is set to High, a good trade-off between speed and texture is obtained, hence the default value of Quality is set to HIGH. Also, we can see that Bitmap is the input format of choice as it is processed the fastest, follo

RxLowpoly

Install / Use

README

RxLowpoly

Table of Contents

Introduction

Lowpoly Samples

Installation

Library Details

JNI

Sobel Operator

Delaunay Triangulation

Usage Examples

Asynchronous call

Synchronous call

Critical Analysis