June 3, 2004


Measurement of Percent Area

This exercise selects features of an image by thresholding, and measures the number of 'red' pixels with the Analyze -> Measure menu.

The image appears washed out. It can be enhanced to make the holes in the filter easier to see.

The features in the image are easier to see. The gray levels have not been changed, as reapplying the Analyze -> Show Histogram  Analyze -> Histogram menu will show.

Either the enhanced image or the original can be thresholded with the same effect, since the number of gray levels is the same. The enhanced image may be easier to use, since the details are more easily seen, and using the thresholding tool is less tedious.

Measure the percent area of the pores in the filter.

Two problems immediately appear. Red pixels are missing inside the pores where they should be, and there are red pixels outside the pores where they should not be.

We will ignore the remaining red dots that lie outside the pores. We will also not check for any slight alteration of pore area that the smoothing might have caused.

Counting and sizing pores with NIH Image


(part of table shown)

Counting and Sizing Pores with ImageJ

This proceedure starts fresh - you might already have the image open from above steps.