Combining Images
  by Dennis Wilkins


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Picture Window and Picture Window Pro provides a very flexible set of functions for combining images that can be used to make panoramas. The Composite transformation has a number of alignment features that enable “splicing” images that do not line up perfectly. When making a panorama, the rotation of the camera causes a change in image perspective. There are a number of automated panorama programs on the market that attempt to correct the perspective and blend each successive image to make a seamless whole. I own a couple of these programs, and have tested a few more, and they generally work pretty well if you rotate the camera through the nodal point of its lens. But I have found in some cases, even using nodal rotation, they cannot seem to make a clean blend. And since they typically use a “lap-dissolve” with the processed image fading gradually from one input image to the next, the results can be less than desirable.

Picture Window and Picture Window Pro will not automatically stitch two or more images together, but the extensive control provided for alignment and even perspective control when combining images makes stitching panoramas easy and more precise than most automated stitching programs.

Stitching provides more than just making wider angle shots . . . it also increases the pixel count of an image. Stitching only two images together from a three megapixel camera can make a five megapixel image with about 20% overlap. And Picture Window doesn’t really require any overlap, although you need enough to see how to align the two images.

The shots below were made in the eastern Colorado plains, of a landmark called the West Pawnee Butte. This butte was a major signpost for the early pioneers traveling west. These shots were made right after sunrise one morning, with the camera set to manual exposure so that there would be no shift in density from one image to the next.

Panorama 1   Panorama 2   Panorama 3

This is not the usual “left to right pan” but is a vertical pan. Before stitching these images together, we need an image window that has a space large enough for the combined three images. The width is known (3008 pixels in each case), but the resulting height will be less than three times the 2000 pixel height of each image because there is considerable overlap. Overlap was used here in order to enable a couple of automatic panorama programs to process this image – neither one produced an image as “clean” as Picture Window, and both required a lot of manual adjustments and clean-up work. Overall, they took as long to complete the panorama as it took me using Picture Window.

The first order of business is to create a new window, 3008 pixels wide by about 4800 pixels tall, more than enough to include the height. This is easy to do . . .