Area and pixel count in Photoshop vs ImageJ

Posted by Andrew Sanchez on
URL: http://imagej.273.s1.nabble.com/Area-and-pixel-count-in-Photoshop-vs-ImageJ-tp5013084.html

Here are results between Photoshop and ImageJ:

In Photoshop, the measurement log shows that the Area of a 100x100 circle
is 5720.  In my histogram, it reads "Pixels: 5640 pixels."  The measurement
scale is set to 1 pixel = 1 pixel.

My project involves counting the number of green pixels in an image and
dividing that number by the total number of pixels in the ROI, in order to
get the percentage of vegetation.  The number shown in the histogram of
Photoshop next to Pixels is the value I've been using as the total number
of pixels.  Since starting to look into ImageJ, I'm worried that this
method is not accurate.

In ImageJ, I removed the scale and get the correct area of 7860.

I am hoping to switch over from using Photoshop to ImageJ, but I need to
first understand why the numbers I get in Photoshop are so different.

--
Thank you,
Andrew Sanchez
Lab Assistant
Center for Ecosystem Science
Northern Arizona University

--
ImageJ mailing list: http://imagej.nih.gov/ij/list.html