How to make a part of the image look negative within the same image

Image processing, astrometry, photometry, etc.
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AgustinZ39
Posts: 3
Joined: 08 Apr 2019, 19:57

How to make a part of the image look negative within the same image

Post by AgustinZ39 » 08 Apr 2019, 20:42

Hi all !!
I am a new user of Astroart 7 and I have a doubt because I want to select a part of an image to enlarge it and put it in negative in the initial image (to highlight that part) but I can not see it in negative. I copy a selection of the initial image, I paste it as a new image and then I enlarge it and I make it negative. Then I copy that enlarged and negative image and paste it in the initial image but when I paste it, the negative is not preserved and it is put with the normal palette.
So I would appreciate someone telling me how I can do it.
Thank you,
Agustin

Dunmunro
Posts: 85
Joined: 10 Jan 2019, 01:11

Re: How to make a part of the image look negative within the same image

Post by Dunmunro » 08 Apr 2019, 21:27

AgustinZ39 wrote:
08 Apr 2019, 20:42
Hi all !!
I am a new user of Astroart 7 and I have a doubt because I want to select a part of an image to enlarge it and put it in negative in the initial image (to highlight that part) but I can not see it in negative. I copy a selection of the initial image, I paste it as a new image and then I enlarge it and I make it negative. Then I copy that enlarged and negative image and paste it in the initial image but when I paste it, the negative is not preserved and it is put with the normal palette.
So I would appreciate someone telling me how I can do it.
Thank you,
Agustin
I think you'll have to use a mask to do that. I'm not that familiar with using masks, but there is some info available via the help files.

fabdev
Posts: 191
Joined: 03 Dec 2018, 21:43

Re: How to make a part of the image look negative within the same image

Post by fabdev » 08 Apr 2019, 21:42

Hi, it could be done, but after that processing you will not be able to adjust the realtime visualization well (because the image will contain both positive and negative parts).
So, I guess that this is the last step before publishing your image.

You could:

1) On the original image: Arithmetic / Scale / Transfer function / 255 (or 65535 if you want to work with 16 bits).

2) On the negative image: Save View, as PNG 8 bit (or 16 bit).

3) Then reopen the negative image and mix it with the original image.

------

About using a mask, you could instead create a Mask, then Arithmetic / Formula, for example:

v = vbkg*3 - v (make some tests with the Preview button).

AgustinZ39
Posts: 3
Joined: 08 Apr 2019, 19:57

Re: How to make a part of the image look negative within the same image

Post by AgustinZ39 » 09 Apr 2019, 00:15

Thank you very much, Dunmunro and fabdev for your answers.
I was able to do what I wanted by using a mask, thanks to fabdev's explanation, with a formula to invert the selected area. But I could not do it by the easiest way to paste an inverted image into the main image.
So I must be doing something wrong, because something like this can not be so difficult !!

http://www.astrosurf.com/cometas-obs/C2 ... _tn_14.jpg

einari
Posts: 21
Joined: 28 Jan 2019, 10:46

Re: How to make a part of the image look negative within the same image

Post by einari » 09 Apr 2019, 06:03

I would do that with Photoshop (or some other similar software).

fabdev
Posts: 191
Joined: 03 Dec 2018, 21:43

Re: How to make a part of the image look negative within the same image

Post by fabdev » 09 Apr 2019, 14:01

A procedure could be:

1) Select the region on your original image.

2) Crop the region, then Invert it with the Formula command.

3) Resize the cropped image.

4) Copy to clipboard the cropped image, select the original image then Paste with the option "Into image".

AgustinZ39
Posts: 3
Joined: 08 Apr 2019, 19:57

Re: How to make a part of the image look negative within the same image

Post by AgustinZ39 » 09 Apr 2019, 19:36

Yes, Einari, with Photoshop it can be done, but I wanted to know how to do it in Astroart !!
And with the new explanation of fabdev it worked perfectly! I just had to adjust the formula "v = vbkg * 3 - v" doing tests and in my case it goes perfect changing 3 by 2.1 ...
Thank you very much, fabdev

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