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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.

 


Due to the fact that Boris Johnson is now our Prime Minister, punctuation, spelling and grammar will never be worried about ever again.  We now have far bigger problems to be worried about.

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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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