After grading an equirectangular image a seam is visible in PTG Viewer

[twalp]

After exporting gigapixel jpeg equirectangular images from PTG, I do non-destructive color and exposure editing in Affinity Photo 2.6.5. I export the result to JPEG and view it in PGT Viewer.  If any of my adjustment layers affect the entire image there is often a visible seam where the two edges meet.  Is there a way to avoid or fix this back in PTG?

[Matthew Rogers]

The problem is, most of the tools in Affinity Photo aren’t 360 aware. And now it’s owned by Canva the chances of it ever being supported are virtually zero.

Matt

On 25 Mar 2026, at 21:29, twalp <trw...@gmail.com> wrote:

After exporting gigapixel jpeg equirectangular images from PTG, I do non-destructive color and exposure editing in Affinity Photo 2.6.5. I export the result to JPEG and view it in PGT Viewer.  If any of my adjustment layers affect the entire image there is often a visible seam where the two edges meet.  Is there a way to avoid or fix this back in PTG?

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[John Houghton]

One way of dealing with this problem is to make a temporary copy of the image that is more than 360 degrees wide, do your adjustments, and then shrink the image back to 360 degrees wide.  E.g. you might copy/paste a section from the left hand side of the image to the right hand side, and likewise copy/paste the right hand side to the left hand side.  Or copy/paste a larger selection to one side, and after doing your image adjustments crop the central portion to the original width and do a shift with wraparound to restore the original centre point.

John

[Erik Krause]

Am 25.03.2026 um 22:29 schrieb twalp:

> If any of my adjustment layers affect the entire image there is
> often a visible seam where the two edges meet. Is there a way to
> avoid or fix this back in PTG?

One way to avoid this is not doing adjustments that act locally. I'm not
familiar with affinity (yet), but anything that acts on shadows
differently than on highlights might cause this effect. Only adjusting
global exposure, contrast or gamma should not cause it.

Recent versions of affinity used to have a spherical mode, where you
could edit panoramas seamlessly.

In recent versions of PTGui pro you can try to use the Patch tool. This
might be difficult for highly structured areas, though.

--
Erik Krause
http://www.erik-krause.de

[twalp]

So what photo editors ARE 360 aware? (I didn't know about this issue until now, but it makes sense. Doh!)

[PTGui Support]

There's one way to work around this: Take your 360 image and extend it
at at the left and right hand side by copying a part from the opposite
side. So you then wider image with some parts repeated at both ends.

Then do your editing, and afterwards crop the image again to the
original dimensions (360 degrees horizontally).

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

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[twalp]

Thank you to all who responded, especially John Houghton and Joost whose answers led me to a solution. 

I tried copy/paste in Affinity Photo 2.6.5 to produce an expanded width image, but the resulting "extensions" differed in color or tone from the original image. Total bafflement, because I had done nothing to the equirect out of PTG other than view it in PTG Viewer. (no seam evident) The color space or whatever must change in the copy/paste process.

BUT, duplicating the original image to a second and third layer, deleting all but a 500 px end strip (left end and right end), and then moving the end strips to the opposite ends of the original image did produce a seamless working image. I beat the heck out of it with adjustment layers, masks, and local/global whatnot to challenge the result. I then used Resize Canvas with it pinned to the center to restore it to an equirectangular image, and exported it. The result plays perfectly in PTG Viewer. 

However, using my 32GB M1 Max MacBook both the copy/paste and the dupe/move processes with a 50K by 25K image are exercises in spinning beachball (busy indicator) watching. Being ignorant about projections and other tech details I'm curious if PTgui can create a 370 X 180 cylindrical image that can be converted to a spherical image later. 

[Erik Krause]

Am 25.03.2026 um 22:29 schrieb twalp:

> If any of my adjustment layers affect the entire image there is
> often a visible seam where the two edges meet.

I played a bit with Affinity 3 using Live Projection: Equirectangular
and was not able to reproduce your problems. Even after using a very
strong "Shadows and Highlights" or USM layer there was no visible seam
line in Live Projection, where I can choose the visible portion same as
in a spherical viewer. And the saved output didn't show a seam line
either. What exactly are you doing to cause this seam line?

[twalp]

Thank you replying AND going to the effort of testing Affinity Photo. I don't use v3 but I installed it to see if its behavior has changed. After trying it I think I can say that editing equirect's in projection mode is the same as in the more familiar v 2.6.5.  

Here's what I do that might differ from what you tried:

I rarely make global changes; most are adjustment layers with masks. For example, painting in a mask to lighten a specific area, or adding clarify and a curve across the distant horizon where haze is almost always present, etc. 

Once I do that, whether in equirectangular projection mode or before switching to it, when I pan around in the spherical image all the masks remain in place and do not move with the image. I could merge all the layer before panning around but what's the point? Plus, when I am working with masks I sometimes need access to more of the image than the FOV in the viewport permits. It is much easier and consistent to work on the entire image, especially when dealing with the horizon. Actually, I cannot imagine editing in equirectangular projection mode other than to make global adjustments --- which has its place, but not in the images I end up working with. 

Thanks again!

[twalp]

Perplexity helped me find a solution that makes Joost's suggestion much easier to do. His recommendation:

Take your 360 image and extend it at at the left and right hand side by copying a part from the opposite side. So you then wider image with some parts repeated at both ends. 

Doing this with an image editor like Affinity Photo takes a lot of time, especially with my 50k px by 25k px equirects. 

Perplexity recommended using Imagik to expand and later crop the image back to the original size.

Here are the instructions if anyone wants to use this technique on a Mac.

1. Install Homebrew (if you don’t have it)

Open Terminal (Applications → Utilities → Terminal).
Paste this command and press Return:
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

Follow the prompts. When it finishes, you should be able to run:
brew --version

If that prints a version, Homebrew is installed.

2. Install ImageMagick via Homebrew

In the same Terminal window:
brew install imagemagick

This pulls a current, precompiled build with JPEG, PNG, TIFF, etc.

Verify that it’s working:
magick -version

You should see version info and a list of supported formats including JPEG.

Now to the scripts to expand and later crop the image(s) by 500px at each end. Note that these scripts are written solely for processing jpeg equirects with the extent: .jpg. The jpeg quality is 95. All jpeg's in the target folder will be expanded into a subfolder named Out. 

1. Create the expand script in ~/bin.  (If the /bin folder doesn't exit, ask AI how to create it.)

Open the nano editor in Terminal:

nano ~/bin/expand_panos.sh

Paste this:

#!/bin/zsh
mkdir -p out
for f in *.jpg; do
  [ -e "$f" ] || continue
  base="${f%.*}"
  noglob magick "$f" -crop 500x%[h]+%[fx:w-500]+0 +repage "${base}_right.png"
  noglob magick "$f" -crop 500x%[h]+0+0 +repage "${base}_left.png"
  noglob magick "${base}_right.png" "$f" "${base}_left.png" +append -quality 95 "out/${base}_expanded_q95.jpg"
  rm -f "${base}_right.png" "${base}_left.png"
done

Save and exit (Ctrl‑O, Return, Ctrl‑X), then make it executable:
chmod +x ~/bin/expand_panos.sh

2. Create the crop‑back script in ~/bin
nano ~/bin/crop_panos.sh

Paste:
#!/bin/zsh
mkdir -p out_cropped
for f in out/*_expanded_q95.jpg; do
  [ -e "$f" ] || continue
  base="${f##*/}"
  base="${base%_expanded_q95.jpg}"
  noglob magick "$f" -gravity center -crop '%[fx:w-1000]x%[h]+0+0' +repage "out_cropped/${base}_cropped.jpg"
done

Save and exit, then:
chmod +x ~/bin/crop_panos.sh

3. Run them from your pano folder
First, ensure ~/bin is on your PATH once (only if this fails):
echo 'export PATH="$HOME/bin:$PATH"' >> ~/.zshrc
source ~/.zshrc

4. Output the equirect(s) from PTGui to a dedicated target folder, like panos. Open Terminal there, which is most easily done in Finder by:

• Open a new Finder window.
• Navigate to the target folder. 
• Ensure that in the Finder View menu you have enabled "Show Path Bar", which displays the entire path below the folder listing.
  (mine: '/Users/(my username)/Documents/Projects/Panos')
• Right-click on the target folder (Panos) and select "Open in Terminal".

To see and verify the contents of the Panos folder in Terminal type:

ls

(That's lowercase LS)

To expand all the jpeg files in Panos by 1000 px (500 on each side) run this command in Terminal.

expand_panos.sh   # builds the out/ folder with expanded panos

5. Do whatever you want to the jpeg image in your photo editor. Do not resize it though!  The resulting output file needs to end up in the same /Out folder from which it came. Since "Saving"  a file in Affinity Photo saves it as a special .afphoto file, which means it contains the original expanded equirect from PTGui along with all the changes (I use adjustment layers for all changes), I export the result to a jpeg to the /out folder and let it overwrite the original.

6. In Terminal, still open to the panos folder, crop off the extended parts of the image:
crop_panos.sh     # builds out_cropped/ with 2:1 crops from out/

The cropped, ready-to-view result will be in the /out_cropped subfolder of Panos.

So far this approach has worked for me every time. I avoid painting masks near the left and right edge of the image, but otherwise I am free to use any tool for color grading all or any part of the image. I use Adjustment and Live Filter layers so all changes are non-destructive. The presence of the extended sections prevents a seam from appearing after it is cropped back to the 2:1 ratio for viewing in PTGui Viewer and further use.

On Friday, March 27, 2026 at 1:02:04 AM UTC-5 PTGui Support wrote: