Difference between revisions of "Stitching 2008 State of the Art"
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Erik Krause (talk | contribs) (Moved text from "How Stitching Works") |
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| − | == | + | == Introduction == |
| − | + | Stitching is about making one large image from several smaller photos. | |
| + | The ambition is to have the fact of individual ingredient photos no longer show through in the resulting image. | ||
| + | This page shows what stitching software actually does. | ||
If you want to know how to achieve this, or what | If you want to know how to achieve this, or what | ||
[[software]] to use, please read a [[Tutorials|tutorial]] instead. | [[software]] to use, please read a [[Tutorials|tutorial]] instead. | ||
What can be done and what quality can be achieved, | What can be done and what quality can be achieved, | ||
| − | this shall be demonstrated step by step with the two | + | this shall be demonstrated step by step starting with the two photos below. |
[[Image:Img08232.jpg|300px]] [[Image:Img08231.jpg|300px]] | [[Image:Img08232.jpg|300px]] [[Image:Img08231.jpg|300px]] | ||
| − | At the time of photography, some [[Photography Guidelines|guidelines]] have been followed that make the photos good | + | At the time of photography, some [[Photography Guidelines|guidelines]] have been followed that make the photos good stitching material. |
---- | ---- | ||
| + | |||
For comparison to stitching proper, the two photos have simply been overlayed in a standard | For comparison to stitching proper, the two photos have simply been overlayed in a standard | ||
image editing and retouching software. | image editing and retouching software. | ||
| Line 18: | Line 21: | ||
[[Image:Img0823xoverlay1.jpg|300px]] [[Image:Img0823xoverlay2.jpg|300px]] | [[Image:Img0823xoverlay1.jpg|300px]] [[Image:Img0823xoverlay2.jpg|300px]] | ||
| − | |||
Please notice in particular the misalignment of geometrical features in the left image, | Please notice in particular the misalignment of geometrical features in the left image, | ||
and the roof misorientation in the right one. | and the roof misorientation in the right one. | ||
| + | |||
---- | ---- | ||
| − | Have a look at the following aspects to see where | + | Have a look at the following aspects to see where proper stitching software can do better. |
| − | + | Such software usually gives a choice of either performing these steps fully automatically, | |
| − | or | + | or provide assistance for optimisations without requiring a try-and-error workflow. |
===Remapping=== | ===Remapping=== | ||
| Line 32: | Line 35: | ||
To project the images onto the same virtual screen, they need | To project the images onto the same virtual screen, they need | ||
| − | to be remapped, as shown above. | + | to be remapped, as shown above. Correcting falling lines as in this example |
is by choosing an appropriate orientation for the virtual screen. | is by choosing an appropriate orientation for the virtual screen. | ||
[[Image:Img0823xstitch3.jpg|500px]] | [[Image:Img0823xstitch3.jpg|500px]] | ||
| − | |||
The relative camera orientation, and the lense parameters | The relative camera orientation, and the lense parameters | ||
are determined from the images overlap area. | are determined from the images overlap area. | ||
| + | Handheld photos are fine. | ||
If the photos have been taken from the same point, | If the photos have been taken from the same point, | ||
expect alignment accuracy of better than a pixel. | expect alignment accuracy of better than a pixel. | ||
| Line 62: | Line 65: | ||
State of the art is a seam mechanism that behaves | State of the art is a seam mechanism that behaves | ||
| − | like a line for small details but averages for large scale | + | like a line for small details but averages for large scale features. |
[[Image:Img0823xstitch6.jpg|500px]] | [[Image:Img0823xstitch6.jpg|500px]] | ||
| Line 75: | Line 78: | ||
This is the overall result, cropped to rectangular shape, | This is the overall result, cropped to rectangular shape, | ||
| − | for a state-of-the-art stitching of | + | for a state-of-the-art stitching of two photos. |
| − | [[Category: | + | [[Category:How it works]] |
Revision as of 13:42, 4 May 2008
Introduction
Stitching is about making one large image from several smaller photos. The ambition is to have the fact of individual ingredient photos no longer show through in the resulting image. This page shows what stitching software actually does.
If you want to know how to achieve this, or what software to use, please read a tutorial instead. What can be done and what quality can be achieved, this shall be demonstrated step by step starting with the two photos below.
At the time of photography, some guidelines have been followed that make the photos good stitching material.
For comparison to stitching proper, the two photos have simply been overlayed in a standard image editing and retouching software.
Please notice in particular the misalignment of geometrical features in the left image, and the roof misorientation in the right one.
Have a look at the following aspects to see where proper stitching software can do better. Such software usually gives a choice of either performing these steps fully automatically, or provide assistance for optimisations without requiring a try-and-error workflow.
Remapping
To project the images onto the same virtual screen, they need to be remapped, as shown above. Correcting falling lines as in this example is by choosing an appropriate orientation for the virtual screen.
The relative camera orientation, and the lense parameters are determined from the images overlap area. Handheld photos are fine. If the photos have been taken from the same point, expect alignment accuracy of better than a pixel.
Exposure
Input images need not have the same exposure, or white balance. Together with vignetting (images are darker in the corners than in the middle) the required corrections can be derived from images with a suitably large overlap area.
Blending
Obviously, there needs to be some kind of seam between the images, but one can do better than a hard seam line (used above) or a feathered transition that affects the image character.
State of the art is a seam mechanism that behaves like a line for small details but averages for large scale features.
In addition, the seam line should be placed intelligently to avoid cutting through objects (like cloud, car or bicycle) that have moved in the time between taking the images.
Overall Result
This is the overall result, cropped to rectangular shape, for a state-of-the-art stitching of two photos.