Image Filtering Using Fourier Transform

In Machine Vision there is a magical trick that involves Fourier transformation of an image and I would like to share it with you today. I learned this long ago from a professor of mine but I remember back then there was not much experience and information about this on the web. Also there was no program that allowed experimenting with Fourier transformation of Images, until I developed an Android application titled Image Transformer, using OpenCV and Qt, which allows you to do just that.

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Image Transformer Update (Color Space Visualizer Added)

I recently updated Image Transformer. New GUI, new functions and lots of fixes and optimizations.

Below are some screenshots that demonstrate its usage.

Here is the description of the recent update as it is seen in Google Play.

This program allows you to perform Fourier transform and color space analysis on images from gallery and taken from camera.

Using this application you can:
* View any image from your images gallery or taken using the camera
* Use basic editing tools to resize or rotate the images
* Use Fourier transformation tab to perform DFT (Discreet Fourier Transform) and perform Inverse DFT on the images
* Apply masks to different parts of the Fourier transformation of the image and perform Inverse DFT to view the changes in the original images
* Perform Canny transform on the images
* Perform Color Space Conversion From/To RGB, HSV, YUV and other major Color Spaces
* Save the result image to your phone’s memory





Notes:
Masking the Fourier transformation can be achieved by drawing rectangles over the transformed image. It is also possible to apply an image that is taken from camera or opened from gallery as a binary threshold mask. Do not forget to perform Inverse Fourier to see the results of masking.

Finally:
This program is intended to be used by image processing and machine vision enthusiasts, researchers and university students who need to experiment with Fourier transformation and Color Space Conversions. It is built totally using open source components such as Qt and OpenCV and parts of the source code can be requested using the “Contact Me” page at my website.

Use the following button to download the most recent version from Google Play.

image transformer download





Image Transformer (Fourier Transform App for Android)

UPDATE: This application is updated. Please read this post for more information.

My new application is a tool for for performing Fourier transformation on images. You can then apply masks to the Fourier representation of image and revert back (perform Inverse Fourier Transform) to see how the image gets affected.

For more information about Fourier Transform you can check out this link.

It is built using OpenCV and Qt and it is programmed completely in C++. I hope it would be useful for Image Processing and Machine Vision enthusiasts, researchers and students. It also contains some useful tips and tricks for programming Android applications using Qt and OpenCV such as:

  • How to open Android image gallery in Qt (Default interface)
  • How to capture images using default Android camera interface
  • How to crop images displayed on a QLabel
  • etc.




Source code (any part of it actually 🙂 ) is available upon request. Please send your requests using the Contact Me page.

Please consider supporting this application by giving a decent rating in Google Play.

For an example of Fourier transform using OpenCV please check out this link.

You can also see this link for more information about Fourier transform.

You can download this application from Google Play using the link below:

https://play.google.com/store/apps/details?id=com.amahta.ImageTransformer

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