I’ve experienced a problem when measured the colour of grapes using ImageJ.
As the photos taken are affected by light, to get a relatively objective colour of the grapes, I’m measuring Hue values instead of RGB.
What I’m doing is:
select the grape area using ‘colour threshold’ --> separate the images into three channels (hue, saturation and brightness) using ‘stacks to images’ to get the separate Hue channel -->measure the Hue value to get the mean Hue.
However, after separating, the dark grapes (due to shrivel) become into white colour (image below) and have very high Hue values. I don’t quite understand why. Strangely, some grapes that are also dark but not so much remain dark after separation and have very low Hue values. This creates problems for my data analysis and I cannot interpret the data in this case. Anyone knows why does this happen, and how to fix it? Is there a threshold for darkness that when it’s darker, the Hue is higher while when it’s lighter, the Hue is lower?
Thanks in advance for your patient reading this!