Abstract
In digital image processing, image enhancement is employed to give a better look to an image. Color is one of the best ways to visually enhance an image. Pseudo-color refers to coloring an image by mapping gray scale values to a three dimensional color space. In this paper we used a pseudo-color technique in frequency domain to enhance ultrasound images. We used three different types of transforms to do this. These are the Fourier transform, Discrete Cosine transform and Walsh- Hadamard transform. After obtaining these pseudo-color images, we applied a high frequency emphasis filter or histogram stretch as a post process. In this paper we used a subjective study to compare images. First we compared pseudo-color images to their original monochrome images. Secondly, we compared all the three different types of transforms. Lastly, we compared the post processing techniques.
Highlights
This paper was based on the idea that the human visual system is more responsive to color than binary or monochrome images
The Fourier transform is the most well-known and widely used transform. This transform decomposes an image into complex sinusoidal terms and these terms include a zero frequency term, called the DC term which related to average value. highpass, lowpass and bandpass filters. (Umbaugh, 2005)
The subjective study was separated into three categories: pseudo-color image vs. monochrome image, histogram stretch vs. high frequency emphasis filters and comparisons of the transforms
Summary
This paper was based on the idea that the human visual system is more responsive to color than binary or monochrome images. We wanted to experiment with the importance of pseudo-color. To create our images we use the frequency domain pseudo color method that was discussed in Dr Scott Umbaughs’ book, Computer Imaging: Digital Image Analysis and Processing. We already had access to a program with the ability to do it spatially. The purpose of this paper is to be able to understand image enhancement with color. We used ultrasound images as gray scale images and used pseudo color technique to enhance them
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