Read color intensity


Here is my situation. I have 10 photos (high quality jpg file, 4M for 4288x2848 pixel) taken at different time of the same sample. A small area of the sample slowly changed from blue to colorless. The color change is quite visibly with naked eyes and now I need number to prove that. I would like to plot color change versus time.

What I can do: ROI (to select the blue area), split channel, run basic “mean, min, max” measurement

I first tried to use the blue value in “plugins, analyze, RGB measurement.” The blue reading dropped over time as I expected. The red seemed random. The green dropped then remained the same.

Then I tried to split channels. To my surprise, the blue channel does not show the blue dot in my sample which means I could not select region of interest. The red and green channel shows the blue dot.

Then I have always assumed the “RGB measurement” is showing all results of three channels, split channels or not.

What should I do? Follow the “RGB measurement” routine? Or play with the “split channels?”

I have read these two posts, though still lost.

Many thanks!
May all good things come your way!

Hi @AmyH

Sorry for the delay in a response… Let’s see if we can get you some help - from me or others.

To start - I think we need a bit more information from you. Specifically - it would be great if you could share an original image file with us - so we can take a better look at your data. Remember - it’s best to always do all your image analysis on the original file format acquired on your system (saving the best data you can… avoiding .jpg’s etc.). Image Acquisition Principles is a helpful page to read over.

Too - if you are interested in only a specific area and then measuring the signal within - be sure to do your Segmentation of that area on a different signal, one that will remain consistent throughout your experiment. Read this older forum post to have a better idea of what I mean here:

It’s a word of caution. :slight_smile:

So again - please share an image and clearly, concisely describe what you wish to measure in your workflow.


Thank you. Here is attached an original image. I cropped the extra part and I am interested in the blue dot in the center.