Select channel as selection in Affinity Photo

[jhazel0705]

Good morning, 

 

I am trying to extract the fire from the image attached, and I want to  keep it looking bright so I wanted to extract only the red channel and then remove everything else.....I have tried the channels panel, but yet I think my gap is how to make a selection of only the red channel....any thoughts from the gurus on how to do this ???

[v_kyr]

On the channels panel select/preview the composite red and do access the right click menu on that list entry (perform a right click on that one), there from the popup menu select the "load as pixel selection" menu point.

[HVDB Photography]

Below a short video showing how it is possible

 

2018-01-01_21-06-23.mp4

[R C-R]

If you really want only the red channel, you will probably end up with something that looks like this:

If that is really what you want, you could do it by selecting the layer, & from the Channels panel, right click on the green & blue channels, selecting to clear them, then right click on the red channel & select Mask from channel. Flatten the document & you should be left with something like the above. This extract red channel.afmacro will do that. (It assumes the jpg layer is the only one in the document & is named "Background.")

[toltec]

Why not select the black and use the rest ?

 

Select > Select Sampled Colour and invert.

 

Brighten it up a bit with an adjustment layer, or two.

[shojtsy]

I think the edges are too dark in the above examples. I got better results by Ctrl-I for Invert, then Filter->Colours->Erase White Paper, then Invert again. Gets the edges more transparent and less dark.