Adding two images

S

SteveJP

Active member
Hi,
I'm wondering if there is a way I can just arithmetically add two images together. (Assuming they are the same size). Perhaps ImageIntegration will do this, but I'm unsure of the underlying mechanism or what parameters I'd have to specify to get this outcome.
Thanks
Steve
 
Steve,

To simply add two images, use Pixel Math.
In the Expression field type the names (exactly as they appear in the Views on your desktop) with a "+" between:
Image1 + Image2

If the images are on your disk, you should open them in PixInsight first... then add them.

Now... having said that- the question of what you are doing "concerns" me... but the above is certainly the right answer. :)

-adam
 
if you want to average them, (image1 + image2)/2 or any other math formula you can think of...

John
 
You can also use ImageIntegration with a little trick. ImageIntegration needs at least 3 files, so the trick is to load each of your two files twice, letting II think it has 4 files
 
ngc1535 said:
Steve,

To simply add two images, use Pixel Math.
In the Expression field type the names (exactly as they appear in the Views on your desktop) with a "+" between:
Image1 + Image2

If the images are on your disk, you should open them in PixInsight first... then add them.

Now... having said that- the question of what you are doing "concerns" me... but the above is certainly the right answer. :)

-adam
Click to expand...

I have actually experimented with that myself and find that simply adding two integrated images together causes the result to be severely blown out (overexposed).
The reason I am doing trying out integration of two integrated (calibrated, etc.) images is because I want to play around with some of my existing data and want a simpler way than to combine all of them into WBPP; I know it is possible but it is a very heavy processing time load and there isn't an easy way of going back and refining input parameters to get the result all right.

Farzad
 
Farzad_k said:
simply adding two integrated images together causes the result to be severely blown out
Click to expand...
This depends on:
  • whether you are adding linear (unstretched) images or stretched images
  • whether or not you check the "rescale result" box in the PixelMath interface
It will almost alway be wrong to add stretched images (because it is very unlikely that exactly the same non-linear modification has been applied to both images - and if it hasn't they will not be "compatible").
Calling ImageIntegration with three or more linear images can achieve exactly the same effect as adding in PixelMath, but with more helpful options available (if you really want to add just two images you have to put them into ImageIntegration twice to get over the 3 image minimum, but the result is the same). You will soon find that trying to achieve anything useful just using PixelMath will take much longer tha WBPP. The new caching facility in WBPP is designed to support the sort of "try-it-and-see" process you are talking about. If you rerun WBPP it will check whether each process in the workflow has already been performed on each file; if the same file has already (in a previous run) been processed with the same parameters, it will be retrieved from cache, not recalculated.
 
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