CS194-26 Project II: Fun with Filters and Frequencies!
Fall 2022
Image Sharpening

When we have a blurry image, one technique that we can use to make the image clear is to utilizing the sharpening technique.
In order to do so:
      1. We construct a low pass filter and perform it on the image to create a blurred image(low frequency).
      2. Use the original image minus the blurred image to get the high frequency part of the image.
      3. Finally, we add the orginal image with the high frequency part times alpha(parameter defined) to construct a sharpened image.

Sample Outputs:
Blurred then sharpened
Blurred then sharpened
Blurred then sharpened
From the result, we can see that blurred then resharp the image will not return the perfect original image. This happens because during the blurred process, it will take away some high frequency details, the sharpen process can only apply to the high frequency that remained on the blurred image, which will not include any high-frequency that lost due to the blurred process.
Hybrid Image

Next, I tried to create hybrid images by combining low frequency of one image with the high frequency of the other. Thus, if we look at the image close, we will se the high frequency image more. If we get far away from the image, we will see the low frequency image more.

Low frequency Image
High frequency Image
Hybrid Image
Low_Frequency FFT
High Frequency FFT
Hybrid FFT

Bells & Whistles
Here are some examples with colored:

Potential Reason of failure:
The low frequency(basketball) has bold edges which will still remain having high frequency after doing low-pass filter and thus remains visiable in the resulting image.

Using color to enhance the effect works better on high-frequency component and it becomes clearer when watching close.

Gaussian/Laplacian Stacks

In order to create a great blending between two images, we need to first implement the Gaussian and Laplacian Stacks.
We can implemenet them by extracting the low and high frequency components of an image, then do the same on the blurred version.

Gaussian Stack for Apple
Laplacian Stack for Apple

In this project, I utilized filters and frequencies and applied them on various of image processing techniques including sharpening, bluring, making hybrid images and blending two images.
I enjoyed the blending process with implementation of multiresulution pyramid.
It is my first time I learned how frequency is used to create results that are blurred or sharpened.

Thank you!!