Intensity transformation as the name suggests, we transform the pixel intensity value using some transformation function or mathematical expression.
Intensity transformation operation is usually represented in the form
s = T(r)
where, r and s denotes the pixel value before and after processing and T is the transformation that maps pixel value r into s.
Basic types of transformation functions used for image enhancement are
- Linear (Negative and Identity Transformation)
- Logarithmic (log and inverse-log transformation)
- Power law transformation
The below figure summarize these functions. Here, L denotes the intensity value (for 8-bit, L = [0,255])
source: R. C. Gonzalez, R. E. Woods, Digital Image Processing
This is a spatial domain technique which means that all the operations are done directly on the pixels. Also known as a point processing technique (output depend only on the single pixel) as opposed to neighborhood processing techniques(like filtering) which we will discuss later.
Applications:
- To increase the contrast between certain intensity values or image regions.
- For image thresholding or segmentation
In the next blog, we will discuss these different transformation functions in detail. Hope you enjoy reading.
If you have any doubt/suggestion please feel free to ask and I will do my best to help or improve myself. Good-bye until next time.