Edge detection is an image processing technique for finding the boundaries of objects within images. This can be achieved by a variety of computer vision algorithms on all kinds of images. Edge detection is a technique used in a variety of real-life applications like medical imaging, finger-print scanning, and of course those snappy filters on social media.

• Add the JitPack repository to your build file / or inside settings.gradle if new gradle system.

allprojects {
  repositories {
    ...
	maven { url 'https://jitpack.io' }
  }
}

• Now add the dependency to the app level gradle file.

dependencies {
  implementation 'com.github.Parneet-Raghuvanshi:Plotline:1.0.0'
}

• First of all cratre an Instance object of Plotline, here just Give you main activity context instead of MainActivity.this.
• implements the PlotlineHandler interface to your class.
• After implementing ovverride the plotlineHandler() function in your class as shown below.

// This is your Activity in which you want to use Edge Detection
public class MainActivity extends AppCompatActivity implements PlotlineHandler {
    
    // inside a class (for example here --> MainActivity.java)
    Plotline plotline = new Plotline(MainActivity.this);
    
    /**
    * Here is your class body
    */
    
    // this function will recieve all the results from pltoline
    @Override
    public void plotlineHandler(Bitmap preImage,Bitmap postImage,String TYPE_CODE) {
}

Plotline have one main Image processing function.

• processImage() This will take a bitmap and give back you the edge detected bitmap.

{
    public Bitmap processImage(Bitmap bitmap) {...}
}

There are 4 types of helper/utility functions for camera/gallery to avoid boiler-plate code, these functions are void and you can get result images from plotlineHandler function.

• openGalleryWithDetection() this function open gallery and then process image.
• openCameraWithDetection() this function open camera and then process image.
• openGallery() this function will only open gallery and will give you the choosen btimap.
• openCamera() this function will only open camera and will give you the clicked bitmap.

{
    public void openGalleryWithDetection() {...}

    public void openCameraWithDetection() {...}

    public void openGallery() {...}

    public void openCamera() {...}
}

There are also 2 types of similar function for url processing, these functions needs the url to be passed, and you can get result images from plotlineHandler function.

• openUrlWithDetection() this function opens a url and then process the image.
• openUrl() this function will only return the bitmap.

{
    public void openUrlWithDetection(String urlString) {...}
    
    public void openUrl(String urlString) {...}
}

To get result in plotlineHandler() function, there are two types of response based on the String parameter TYPE_CODE where :-

• if TYPE_CODE = "DETECTION" then the result is of a function with Edge Detection and you will get bot Bitmap non-null

  • preImage = unprocessed raw image Bitmap.
  • postImage = processed imge Bitmap (Edge Detected).

• else TYPE_CODE = "BROWSE" then the result is of utility like to open camera/gallerry/url and get raw image bitmap only.

  • preImage = unprocessed raw image Bitmap.
  • postImage = null this time.

This is the most interesting part to know :) believe me.

Edge Detection can be achieved by a series of operations performed on the image bitmap in the form of integer byte arrays.

Such of these operations are mentioned below.

• Thresholding
• Sobel Edge Detector
• Gaussian Smoothing/Convolution
• Canny Edge Detector

Always open for Discussions : 😊 Parneet Raghuvanshi