Step 4 - Fine tune the stitched image

Well, if you’re at this step, you probably have ghosts and/or overlaps that didn’t align properly. It’s probably best to open each overlap region and correct its problems in turn.

We suggest saving your project occasionally as you work on the overlap regions.

To open the first overlap region, click on its top or bottom edge (see the Stitch command). Once the overlap region is open, start by examining the overall alignment.

Correcting overall alignment

If the overall alignment is wrong, you must adjust it manually. Manual adjustment is possible only if fine tuning has not been performed, so if you selected Automatically fine tune on the Fine tuning properties dialog you’ll need to use the Clear fine tuning command to remove the fine tuning of this overlap region.

Use the LEFTARROW and RIGHTARROW keys to manually align the two images one pixel at a time. Hold the SHIFT key to move the images 10 pixels at a time. Hold both SHIFT and CTRL to move 100 pixels at a time. When you get close, nudge the images around one pixel at a time until you get the sharpest image in the middle of the overlap region.

Fine tuning

If you didn’t use automatic fine tuning or if you cleared it to correct overall alignment, you may want to try the Fine tune command now. The fine tune command tiles the overlap region and adjusts the alignment within each tile independently. It displays a small rectangle representing each fine tuning tile. A line radiating from the center of the tile shows the direction and magnitude of the adjustment. The Panorama Factory may abandon some tiles if it cannot achieve a reasonable alignment.

Here’s an example of an overlap region with ghosting and the fine tuned result.

To remove the inconsistently adjusted tiles, move the mouse over the edge of the tile and hold down the CTRL key to get the delete cursor . Click to delete the tile.

Drawing new tiles

You can draw new tiles by click-dragging when away from existing tiles. The cursor shows an ordinary arrow to indicate that you can draw a new tile. In the example, the clouds have offsets that are large enough to cause The Panorama Factory to abandon them (probably because the clouds moved between the time the first and second images were made). By drawing larger tiles, The Panorama Factory gets enough context to compute the correct adjustment.

Sometimes you’ll have an overlap region that is so poor that you have to draw all the fine tuning tiles yourself. The best places to draw overlap tiles are where there are strong horizontal and vertical elements, e.g. a corner of a building or where sidewalk cracks intersect.

Editing tiles

When you draw a tile, The Panorama Factory tries to determine the alignment adjustment. You may disagree with its alignment. In this case, there are two strategies you can follow.

You can edit the tile to stretch or shrink it and hope that The Panorama Factory does a better job on the enlarged or reduced tile. To edit the tile, move the cursor over a side or corner of the tile. The cursor changes to indicate that a dragging operation will change the size of the tile:

If you can’t convince The Panorama Factory to make the right adjustment you can adjust the tile manually with these steps:

1. Move the cursor over the edge of the tile so that the tile highlights.
   
2. While the tile is highlighted, use the LEFTARROW and RIGHTARROW keys to control the adjustment one pixel at a time. Hold the SHIFT key to change the adjustment 10 pixels at a time. Hold both SHIFT and CTRL to change it 100 pixels at a time. When you get close, nudge the adjustment around one pixel at a time until you get the sharpest image in the middle of the tile.

The Panorama Factory fills in the gaps

The Panorama Factory will fill in the adjustment between tiles by interpolating and extrapolating from the surrounding adjustments. This means that a few tiles may be enough in regions where the adjustment changes slowly, but more tiles are needed where the adjustment changes rapidly.

Next seam...

When you’re happy with the adjustment of the seam, use the Next seam command to advance to the next seam (to the right) or the Previous seam command to return to the previous seam (to the left).

Approve

When you’re happy with the all of the seams, use the Approve command to redraw the stitched image (or just double-click it from the computed thumbnails pane).

Adjust blending region boundaries

Sometimes an overlap region will have a ghost you just can’t eliminate with fine tuning. If an object (e.g. car or person) moved between the times you made the two photographs, its position and/or size will differ in the two images. There’s really no way to adjust the images so that features line this will align sharply. You can sometimes eliminate these ghosts by adjusting the boundaries of the blend region.

You make these adjustments when you are looking at the entire stitched image. The overlap regions are displayed as rectangle (see the Stitch command). Move the cursor over a side of the overlap region that has the ghost. The cursor changes to indicate that dragging will change the width of the rectangle: .

You can include or exclude portions of the lefthand image from the blending region by moving the left edge of the rectange. You can include or exclude portions of the righthand image by moving the other edge. You cannot, however, enlarge the rectangle beyond the boundaries of the image overlap. If you try, the rectangle edges will snap back.

>> Step 5 - Crop the stitched image

Revised: October 12, 1999