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How do I make a composite from separate RGB layers

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I have not been able to find any information in help files or video tutorials of how to make a composite image from separate RGB layers. I've done this in PS but can't seem to find a way to do this with affinity. I've imported my RGB Astronomy images into a layered RGB image and filled each layer with color in the channels section. I just cannot figure out to whit's end how to combine them into a composite so I can finish processing the images. Flatten or merge don't seem to work. Can anyone point me in the right direction?

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  • 1 month later...

I am new to AP but very experienced in astronomical image processing and have just derived a way to do this that produces correct results

Assuming each of the R G and B channel files have been aligned, stretched, pre processed for flats, bias etc... and are in-compressed bring each file into AP separately and convert to RGB 16bit mode

Go into the red file and ensure channels is visible

duplicate the background layer and name it EG - Red layer

Delete the main background layer

In the channels section disable all channels (editable and view) except the blue and click the blue channel

Go select all delete

Now click the green channel and make it editable and disable the blue channel

Select all - delete

Click the reset button in channels

Document flatten

Now do the same for the Blue and Green but change the above by deleting the non required channels ie Blue - delete the Red and Green channels etc

You should now have 3 correctly represented colour images

Copy and paste the Blue image into the red image as a layer and the green image into the red image as a layer

This will now become your RGB main image

In this RGB main image change each layer to Layer Mode ADD

Now you have a full RGB image


PS - Group the 3 layers and change the group mode to normal then you can amend each colour layer as needed -ie Change blend amount to balance colour mix

BTW - often Blue needs to go above 100% blend - just duplicate the Blue layer and reduce its opacity


This is more longwinded than PS so write a macro and all is good, this will also give much more control over each colour and blending etc, IS also non distructive



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Dr. Astronomy, Thanks for the information. I have tried several different methods and I get a few steps further each time but not as quick if I were in PS CC I'm not fond of PS and I am going to give your method a try since I enjoy using Affinity a whole lot better than PS. Yes, a little long winded but if it works than a macro is in order. Thanks again.

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Thanks for the macro - great

Unfortunately past command doesn't work on my pc - just gives a vastly magnified image of the pasted file which cannot be resized so I have to bring each file in separately.


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Dr. Astronomy

A couple of issues while trying to use the information you provided.

1. The macros are not a recognized format while trying to import each of the files into the macro library. The extension must be .afmacros not afmacro. Otherwise the AF import 

does not recognize the file.

2. If I rename the extension to .afmacros then I get "Unexpected Macros Format' error while importing the file to add to macros library. The import function now sees the extension but get the error.

3. I tried the initial steps you outlined above on you post from March 4th disabling the channels does not work so I have not been able to figure out what is going on from your process to make corrections to it.


I have each image layer in greyscale, 16-bit and mode set to RGB ready to covert to individual layers for LRGB

I use a much more robust tool (Astro Pixel Processor) tool for stacking and registering all my images before importing each of the LRGB & Ha images into Affinity.

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I successfully ran your macro after converting each image to RGB/16, re-saving the tiff file then load and run the macro over the red layer. Your macro was simple and efficient. Now I have a composite I can continue to post- process. I should be able to modify this macro to add the Luminance, Ha, OIII, and SII layers as well

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  • 2 years later...

I have combined the images from the Juno Jupiter space mission that come as 3 mono images for the Red, Green and Blue spectrum and been able to put them together as a 16bit colour image.

1. Create a new stack containing the three images (Red component, Green component, Blue component)

2. Convert the stack to 16 bit RGB

3. Open the stack and select a channel for one of the image layers in the stack. Clear the colours not for that colour (ie - clear blue and green for the red channel etc). Do the same for the other two colour layers.

4. Change the stack to Range or Total

5. Use "merge visible" to create a new layer and work with that.


I have made a short video that demonstrated how I did this. 


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