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Computer Vision Metrics: Chapter Two (Part B)

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For Part A of Chapter Two, please click here.

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Polygon Shape Family Pre-Processing

Polygon shapes are potentially the most demanding features when considering image pre-processing steps, since as shown in Table 2-1, the range of potential pre-processing methods is quite large and the choice of methods to employ is very data-dependent. Possibly because of the challenges and intended use-cases for polygon shape measurements, they are used only in various niche applications, such as cell biology.

One of the most common methods employed for image preparation prior to polygon shape measurements is to physically correct the lighting and select the subject background. For example, in automated microscopy applications, slides containing cells are prepared with florescent dye to highlight features in the cells, then the illumination angle and position are carefully adjusted under magnification to provide a uniform background under each cell feature to be measured; the resulting images are then much easier to segment.

As illustrated in Figures 2-4 and 2-5, if the pre-processing is wrong, the resulting shape feature descriptors are not very useful. Here are some of the more salient options for pre-processing prior to shape based feature extraction, then we’ll survey a range of other methods later in this chapter.

Figure 2-4. Use of thresholding to solve problems during image pre-processing to prepare images for polygon shape measurement: (Left) Original image. (Center) Thresholded red channel image. (Right) Perimeter tracing above a threshold

Figure 2-5. Another sequence of morphological pre-processing steps preceding polygon shape measurement: (Left) Original image. (Center) Range thresholded and dilated red color channel. (Right) Morphological perimeter shapes taken above a threshold

  1. Illumination corrections. Typically critical for defining the shape and outline of binary features. For example, if perimeter tracking or boundary segmentation is based on edges or thresholds, uneven illumination will cause problems, since...
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Dear Developers, 

I am new in field of computer vision and would be grateful to you if you please provide me answer to following questions

1. What is standard illuminant ?

Ans ) I have read about it in wikipedia and this article but could not understand it completly. In other words I do not understand practical application of standard illuminant.

2. What is Norm CIE1931 ? 

3. What role does standard illuminant play in Norm CIE1931 ? 
4. What is if  when I want to measure using CIE 1931 and do not have standard illuminant ?


I would be grateful to you if you please provide me some reference where I can get answers of above questions or provide me their answers.


Thanks a lot !!