PanEdit Lite: Image Stitching

Automated Stitching Controls

The automated stitching controls consist of four parts:

The Start/Stop button is used to start the automated stitching calculations. This button can also be used to cancel a stitching calculation in progress.

The progress bar shows the extent of the progress made towards completion of the stitching calculations for a particular seam. If the "Align - All Sides" option is in effect, then the Progress bar must be completed for each seam in the panorama.

The appearance of the Search Range and Pattern Size slide bars depend on the Align setting. If the "Align - All Sides" option is selected, then these controls appear as shown in the following figure:

If the "Align - Selected Seam" option is in effect, then these controls appear as shown in the following figure:

Each of the settings provided by the Search Range slide bar and the Pattern Size slide bar are described below.

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The Start/Stop button

Clicking the "Start" button starts a search for the best alignment for a pair of adjacent images. The extent of this search is determined by the Alignment option (All Sides or Selected Seam), the Search Range setting, and the Pattern Size setting.

While this search is in progress, the "Start" button changes to a "Stop" button and the progress of the search for the current seam is shown in the progress bar. Clicking on the "Stop" button halts the current search. Any calculations for the current seam will be discarded, but results obtained for previous seams are retained.

One is free to browse around the scene while the stitching calculations are in progress. Depending on the Search Range and Pattern Size settings, the panoramic image seen in the main window may be updated for every seam, or just once after working on all seams. The cursor changes to an hour glass (wait cursor), and one cannot browse around the scene while the panoramic image is being updated.

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Search Range

The "Search Range" control determines the maximum horizontal and vertical adjustments to be considered when seeking the best possible alignment of two adjacent images. If the "Align All Sides" setting is in effect, the search range choices are:

If the "Align Selected Seam" setting is in effect, the search range choices are:

The broader the search, the longer it takes to complete the stitching calculations, and a narrow search provides a faster stitching calculation. Consequently, the goal is to make the search ranges as small as possible without excluding the optimal aligmnent of the images sharing each seam.

Initially, it is usually necessary to use a slow broad search because the initial images are typically far from the optimal alignment. After the slow initial "Broad" search, however, it should be possible to select the much faster "Narrow" or "Tweak" settings to refine the alignment. The "Tweak" setting is so fast that it can easily be repeated multiple tmes until the seams converge on an optimal alignment.

After a "Broad" or "Narrow" search, it can be useful to click on the Minimize Adjustments button to redistribute some of the adjustments around the entire scene to minimize the amount of adjustments being made to each individual seam.

The "Disable" setting allows the alignment conditions for one or more seams to be set manually and then frozen while the automatic stitching calculations are applied to the remaining seams.

In order to exploit the "Per Seam" setting, first select the "Align Selected Seam" option. Then visit each seam and set the search range slide bar to the most appropriate setting for the selected seam. This is most useful for disabling one or more seams that may require manual intervention. Then switch back to the "Align All Sides" option, set the Search Range slider to "Per Seam", and click on the Start button.

The "Custom" setting allows an advanced user to specify the actual horizontal and vertical search ranges to be used for each seam. This setting provides the ultimate control over the search range parameters, but this setting should rarely if ever be needed in practice.

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Pattern Size

The alignment calculation compares a rectangular patch in the left side of one image (the "Right Image") to a similar area in the right half of the adjacent image to the left (the "Left Image"). The size of this area affects the speed of the stitching calculations and the sensitivity to details above and below the center of each image. The following choices are provided when the "Align All Sides" option is in effect:

When the "Align Selected Seam" option is in effect, the "Per Seam" setting is replaced by a "Custom" setting which allows an advanced user to specify the pattern size numerically. The "Custom" setting provides the ultimate degree of control over the pattern size, but this setting should rarely if ever be needed in practice.

The larger the size of the pattern, the slower the stitching calculations. The default pattern size is "Medium". If there are easily recognizable patterns in the central portions of the overlapping areas shared by adjacent images, then the stitching calculatons may be accelerated by selecting the "Small" pattern size. If the central portions of the overlapping areas shared by a pair of adjacent images lack any distinctive features, then it may be necesary to select the "Large" pattern size to detect features beyond the central 1/3 of the image height.

Return to
Automated Stitching Controls (top).
Return to AutoStitch dialog.
Return to Panorama stitching tool.
Last modified January 13, 2000.