Image J Colour Threshold is not Working



Hello everyone,

recently I installed ImageJ on my computer to quantify certain colours for
my histological analization. Unfortunately, the item “Colour threshold
(Image>Adjust>Colour threshold” isn’t working. In my case the colour
spectrums in the boxes are missing. Do I need to install any Plugin for this
purpose? If yes, which one? For a better understanding of my problem I uploaded the following picture:ImageJ%20Colour%20Threshold

Thank you in advance for your support.


are you sure you are opening an RGB color image? I get the same behavior when I try to open the “Colour threshold” on an image that is not RGB? Maybe you can make a available an input image. What is the ImageJ version you are using?
Best regards,


Hello heartresearch,
Just click the color space button changing it to RGB and there ya go.


What Volker said. You get the histograms empty when there is no image or the image is not a colour one.


Hi Volker,

thank you for your quick response. Actually I don’t know whether it is an RGB colour Image. My picture looks like this (see the attachment). My colleague using another computer was able to analize the picture. The name of the programm is ImageJ-win64. Unfortunately the version is not mentioned here. But it should be the latest one.


Good day,

would you mind telling us what

My colleague using another computer was able to analize the picture

“analize” means?

If yes, of what?




Hi Bob,

I wish it would be as simple as you explained. Once I do it this appears:


Hi Herbie,

sure. Analizing means in this case quantifying the “blue” color in the picture. By that we can quantify the amount of fibrosis in the tissue.



would the Magenta channel image help?

Actually I can’t see much blue in your posted sample image and using the Blue channel appears not very convincing:




What was stated before: your problem is that the image is not an RGB image, but a 3 channel composite (the red letters on the image info indicate that: “1/3 (Red)”).
Convert it to RGB and the thresholder will work.


Thank you Herbie for your efforts, Unfortunaly it will not work for my analizes. I have to use either the red-green-blue (RGB) function or the HSB funtion.


I have to use either the red-green-blue (RGB) function or the HSB funtion.

Who dictates this or why is this so?

I think what you do depends on what you wish to obtain – no?




Sure. But supervisor tought me this method. Since I am a beginner I don’t wish to deviate.


For the third time…


Thank you gabriel for your support. I’m trying to figure out how it works. My pictures are in TIF-format. Do you have any suggestions how to do it?


Image>Type>RGB Color


Thank you so much my friend. It worked!!