Channel Extraction Help

[Scooot]

My aim is to
Extract the red channel from a debayered DSLR xisf file
Apply a star mask to it
Use Morphological transformation on it to remove the red rings around my stars
Recombine the red channel with the other channels to recreate the RGB image.

I’m falling at the first hurdle. When I use channel Extraction to extract the red channel the resulting images are grey scale. If I try and recombine the extracted grey scale images with rgb combination it won’t work, (not surprisingly) because they’re grey scale.

I’d be grateful if someone could tell me how to extract the red channel so I can work on it and then recombine it.
Richard

[bulrichl]

Use this for recombining:

https://pixinsight.com/doc/tools/ChannelCombination/ChannelCombination.html

Bernd

[Scooot]

Use this for recombining:

https://pixinsight.com/doc/tools/ChannelCombination/ChannelCombination.html

Bernd

Thanks Bernd,
That won’t recombine the images I extracted with channel Extraction because they’re grey scale.

[pfile]

why not? you choose each channel's mono image in the R/G/B fields of that process.

rob

[oldwexi]

If you read in the linked document the paragraph:
Channels / Source images
the second line tells you for ChannelCombination all
3 channels must be GRAY monochrome !

Also with ChannelExtraction you will get 3 gray monochrome images
the R the G and the B part.

You process the gray R Channel and than do the recombination of these 3
monochropme channels to a RGB image.

I think you assume the extracted R channel must be red,
the extracted G channel must be green  etc...
Thats a misunderstanding.

Gerald

[msmythers]

Richard

You need the blue and green channels also to recombine using the ChannelCombination tool.  If all you have is the red channel image you can use PixelMath the replace the existing red channel in an rgb image. Here I extracted the red channel, enhanced the red channel in Curves and then replaced the original red channel with the Curves red channel and created a new image called RedEnhanced.



Mike

[Scooot]

Thanks everyone, I was pressing apply in channel combination instead of apply global. If I just press apply I get the error message about the grey images. It had to be something simple 

So the red channel Extraction is just grey scale. I presume I just have to use MT on a trial and error basis then to try and reduce the red rings as I can’t see them on the red channel.

[Scooot]

Richard

You need the blue and green channels also to recombine using the ChannelCombination tool.  If all you have is the red channel image you can use PixelMath the replace the existing red channel in an rgb image. Here I extracted the red channel, enhanced the red channel in Curves and then replaced the original red channel with the Curves red channel and created a new image called RedEnhanced.



Mike

Thanks Mike, my plan was to extract all 3 channels, alter the red, then recombine all 3. Which seems to be possible using channel Extraction and combination. But if not I’ll certainly look at using pixelmath.

[msmythers]

Richard

Yes the ChannelExtraction and ChannelCombination tools do that. PI has many ways of doing what seems to be the same thing but it really is up to the user to decide which is best for there needs.



Mike

[Scooot]

If you read in the linked document the paragraph:
Channels / Source images
the second line tells you for ChannelCombination all
3 channels must be GRAY monochrome !

Also with ChannelExtraction you will get 3 gray monochrome images
the R the G and the B part.

You process the gray R Channel and than do the recombination of these 3
monochropme channels to a RGB image.

I think you assume the extracted R channel must be red,
the extracted G channel must be green  etc...
Thats a misunderstanding.

Gerald

Thanks Gerald, I did indeed expect the R channel to be red, but when I realised it wasn’t I was still surprised I couldn’t recombine them, because of my error of course.

[Scooot]

why not? you choose each channel's mono image in the R/G/B fields of that process.

rob

Thanks Rob, yes I was being a bit of an idiot. When I got the grey images error message it didn’t occur to me I was pressing the wrong apply button.

[Scooot]

Use this for recombining:

https://pixinsight.com/doc/tools/ChannelCombination/ChannelCombination.html

Bernd

Thanks Bernd, you are of course correct. I hope I didn’t come across as rude, it was not my intention.

[pfile]

why not? you choose each channel's mono image in the R/G/B fields of that process.

rob

Thanks Rob, yes I was being a bit of an idiot. When I got the grey images error message it didn’t occur to me I was pressing the wrong apply button.

no big deal - in fact i should have mentioned about the global apply button. it's a concept that takes a bit of getting used to, you're not an idiot

rob