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Select pixels with defined RGB values


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Hello,

is there any possibility to select pixels with specific RGB values in Affinity Photo?

For example, in an picture from a fluorescence microscope, I would like to select all pixels with RED values >251.

I already tried with mask followed by a brush with different red values, but this did not work.

Unfortunateloy, with "Select/Color Range/Red" I cannot define the minimum red level of the selection. Seems to be a fixed value.

Any idea?

Regards,

Jens

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Can you upload a sample image. 

My fluorescence microscope is stored in the garden shed at the moment and it's raining.

 

To save time I am currently using an automated AI to reply to some posts on this forum. If any of "my" posts are wrong or appear to be total b*ll*cks they are the ones generated by the AI. If correct they were probably mine. I apologise for any mistakes made by my AI - I'm sure it will improve with time.

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On 5/16/2019 at 8:23 PM, >|< said:

Here's a macro: Select pixels above some red threshold.afmacro

Select a Pixel object then run the macro. If another type of object is selected then it will be rasterised at the beginning of the macro. The red threshold defaults to 98.431%, which was set by entering "251/2.55" (without quotes) in the percentage field of a Threshold Adjustment when recording the macro.

 

 

Thanks for sharing your idea. Unfortunately, this is not accurate enough. With a threshold of 94%, only pixels with a red value of 255 are selected. With 93%, pixels with red values >237 are selected.

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On 5/16/2019 at 5:17 PM, carl123 said:

Can you upload a sample image. 

My fluorescence microscope is stored in the garden shed at the moment and it's raining.

 

Thanks carl123 for this valuable posting. I assume your other 2296 postings are of similar meaningfullness.

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Just tried again. It works, but only with your pre-defined 98%. When I enter any other number directly into the field which pops up after starting the macro, nothing changes. It only works when I pull the slider with the mouse. But this is not accurate enough (I think the macro takes into account your calculated 98,431%, although only 98% is shown).

However, your macro seems to be the perfect solution for me, if only I could change the 98% to different numbers, and I need it also for other colors.

Could you explain the single steps to create this macro? Obviously, you did not do it via "Select/Select Sampled Color...".

 

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