Basic Method to Detect Edges of an Image

As you may have studied in subjects like Operation Research or might have experienced, the changes occur only at edges. And hence to detect these edges we need to track the drastic change in pixel value. Boundary or an edge will have a sudden abrupt change in pixel value.

In the first stage of edge detection, the image is cleaned from noise by applying some filters. But also need to remember that not all edges will have a distinct change from its neighboring pixels. So there are problems with false edge detection, missing actual edges etc.

Two major methods widely employed in Edge Detection  :-


  • Derivative Method :-  In this method, we take the derivative w.r.t to time. We know that derivative yields maximum location which might correspond to an edge. If we take the same derivative one more time i.e twice on original, maximum turns to zeros. Hence one more approach it to take second derivative and look for maximum zeros. This is nothing but Laplacian Approach.
  • Gradient Method :- Here it looks at nearby pixels to find the changes in pixel value. If value corresponding to them are large, then it is a probable edge.

Comments

Post a Comment

Popular posts from this blog

Mini Project for Image Processing Beginners

A short project for Engineering graduates. Take an MRI Scanned image or a X-Ray image of healthy person as well as a patient and compare the pixel values, edges etc. This will help you understand the general values of a healthy body. Using that as mean or median, try to create an diagnoses software using these images as input. I will add the sample code or algorithm for your reference. So keep checking the blog for more.
Read more

Program to convert image byte array to PDF

Simple sample program to convert image byte array to PDF         //input path. path where byte array is saved         String pathOfByteArrayFile = "/home/inputByteArray.txt";         //output path. path where rendered you need to save . Output PDF should render properly         String outputPDFPath = "/home/output.pdf";         try         {             File file = new File(pathOfByteArrayFile);             FileOutputStream fout = new FileOutputStream(outputPDFPath);             byte[] bArray = Base64.decode(FileUtils.readFileToByteArray(file));             fout.write(bArray);             fout.close();             assertFalse(false);         }         catch (Exception e)         {             //your logic for failure         }
Read more

Program to convert base64 to Image and vice versa

Code snippet: This method decodes the base64 string into the bytes and converts it into an image .      * Note: this method expects input to be an encoded Image in base64 format. It can't work with other other files encoded in base64 format ByteArrayInputStream bis = new ByteArrayInputStream(Base64.getDecoder().decode(base64data)); BufferedImage img = ImageIO.read(bis); bis.close(); This method encodes the PNG image to base64 format ByteArrayOutputStream output = new ByteArrayOutputStream(); ImageIO.write(image, "PNG", output); String encodedString = Base64.getEncoder().encodeToString(output.toByteArray()); output.close();
Read more