On 11/30/10, Mark Phillips wrote:

P.S. I have also tried Hugin, which I could not get to work,

What exactly didn't work?

Alexandre Prokoudine http://libregraphicsworld.org

On 11/30/2010 01:09 AM, Mark Phillips wrote:

I followed the instructions for creating a panorama from 4 pictures in the Beginning Gimp book (Apres - AkkanaPeck) and it looks great except I have a dark vertical shadow where two of the images meet. How do I get rid of it? I am working on Linux Debian testing with Gimp 2.6.10.

Briefly, this is what I did: 1. Make an new image a little larger than 4 X the width of one picture 2. Add first picture as a layer.
3. Add the second as another layer
4. Overlap image two over image one until they line up. 5. Add layer mask to image 2
6. Add gradient to layer mask - black to white from edge of second image to 3/4 of the way to edge of image 1 7. Repeat as needed for each new image

By looking at the image, I would say the vertical band of darkness is the area of the gradient/overlap of the two images. I am a complete novice at this....

Thanks!

Mark

P.S. I have also tried Hugin, which I could not get to work, and the gimp panorama plugin, which produce the same problem as above.

Your shadow on the seam is caused by a general color mismatch between the right part of the left image and the left part of the right one. Creating panoramas requires to set the camera in manual mode to make sure it won't change exposure parameters between the various shots. And even once you have done that you still have shadow problems to sort out because your photo has vignetting (slightly darker in the corners) and the seam may be done between the border of a picture (dark) and a more inner part of the next (slightly lighter). And this assumes of course that you have got the geometry right, and corrected any tilt in the pictures, etc...

To make it short, assembling panoramas in Gimp is a lot of hard work. The only pictures that aren't too hard to assemble in Gimp are those from a flatbed scanner.

Invest you time in making Hugin work. This will be a lot more rewarding in the end.

Mark Phillips writes:

P.S. I have also tried Hugin, which I could not get to work,

[ ... ]

I had a lot of trouble creating the points. I installed Hugin from the Debian respositories (v 2010.0.0.5045) and out of the box I got the error message about the non-free point calculating module. I then installed

I've found, with Hugin, that either it does brilliantly in automatic mode, finding all the control points and doing all the stitching on its own, or else it fails miserably for no obvious reason and recovering and making it work is quite tricky. I seldom hit cases where setting manual control points makes that much difference, even when the control points it chose seem poorly placed.

One failure mode I see a lot turned out to be just the projection: it stitched all the images reasonably but then smushed the result up against the top so you couldn't see anything. I ended up upgrading to a newer version at http://www.tatteredmoons.org/hugin/deb which gave me more options for recovery, but it still ended up being more trouble than it was worth in a lot of cases. I wrote a couple of articles on on it that might help: http://www.linuxplanet.com/linuxplanet/tutorials/7162/1/ http://www.linuxplanet.com/linuxplanet/tutorials/7170/1/

Ofnuts writes:

Your shadow on the seam is caused by a general color mismatch between the right part of the left image and the left part of the right one. Creating panoramas requires to set the camera in manual mode to make sure it won't change exposure parameters between the various shots. And

"Requires" is a bit strong -- I've stitched lots of panoramas from handheld auto-exposed sets. It certainly makes it easier.

But if you (Mark) have the layer masks in place, you shouldn't get a sharp vertical band where two images meet -- the gradient in the layer mask should take care of that. So it might be worth checking your layer masks (e.g. alt-click on the mask's thumbnail, or use Show Layer Mask) to make sure the gradient is really where you expect.

For instance, you can see the sky change color about 1/3 from the left in http://shallowsky.com/images/anasazi/confluence/confluencepan-big.jpg but it's not a sharp band because of the layer mask gradient.

Sometimes it helps to make the gradient wider, or to take a big fuzzy brush and paint some grey to make the two areas merge more smoothly. If it's just one image causing the problem, you can use Brightness/Contrast, Levels or Curves on it to make it better match the image next to it; but in a panorama with a lot of images, that gets tedious fast if you want them all to match, and you still end up with color changes like in my confluence pan.

To make it short, assembling panoramas in Gimp is a lot of hard work.

[ ... ]

Invest you time in making Hugin work. This will be a lot more rewarding in the end.

I've found that I can usually get reasonably okay looking panoramas from GIMP without too much work, just some fiddling with the gradients and a little hand painting in the mask. But they're not perfect, and I do agree, Hugin does a much better job than you'll get with GIMP. And when Hugin works, it's super easy. These days, I always try Hugin first for panoramas, and I only fall back on GIMP for the occasional set that Hugin won't handle.

...Akkana

On Mon, Nov 29, 2010 at 6:14 PM, Ofnuts wrote:

On 11/30/2010 01:09 AM, Mark Phillips wrote:

I followed the instructions for creating a panorama from 4 pictures in the Beginning Gimp book (Apres - AkkanaPeck) and it looks great except I have a dark vertical shadow where two of the images meet. How do I get rid of it? I am working on Linux Debian testing with Gimp 2.6.10.

Briefly, this is what I did: 1. Make an new image a little larger than 4 X the width of one picture 2. Add first picture as a layer.
3. Add the second as another layer
4. Overlap image two over image one until they line up. 5. Add layer mask to image 2
6. Add gradient to layer mask - black to white from edge of second image to 3/4 of the way to edge of image 1 7. Repeat as needed for each new image

By looking at the image, I would say the vertical band of darkness is the area of the gradient/overlap of the two images. I am a complete novice at this....

Thanks!

Mark

P.S. I have also tried Hugin, which I could not get to work, and the gimp panorama plugin, which produce the same problem as above.

Your shadow on the seam is caused by a general color mismatch between the right part of the left image and the left part of the right one. Creating panoramas requires to set the camera in manual mode to make sure it won't change exposure parameters between the various shots. And even once you have done that you still have shadow problems to sort out because your photo has vignetting (slightly darker in the corners) and the seam may be done between the border of a picture (dark) and a more inner part of the next (slightly lighter). And this assumes of course that you have got the geometry right, and corrected any tilt in the pictures, etc...

To make it short, assembling panoramas in Gimp is a lot of hard work. The only pictures that aren't too hard to assemble in Gimp are those from a flatbed scanner.

Invest you time in making Hugin work. This will be a lot more rewarding in the end.

Hmmm....that is very discouraging....the panorama from Gimp looks great, except for the two vertical black shadows where three pictures were joined. The sahdows are over water and sky.....Gimp is so powerful, I am surprised there isn't some way to get rid of them.

Mark

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I think Hugin, especially the latest version is a great application and the web site has a fine selection of tutorials but going back to more basic stitching why not try the Pandora script. It takes some but not all of the work out of joining images. Still best to do as much prep as possible, straightening, rotating, adjusting colour. Several tutorials around, this was my take on it. Appologies for it being a bit long winded.

http://www.youtube.com/watch?v=zBma6CT3mjY