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enblend

NAME

enblend - combine images using a multiresolution spline

SYNOPSIS

enblend [OPTIONS] -o output-file input-files...

DESCRIPTION

Enblend overlays multiple TIFF images using the Burt & Adelson multiresolution spline. This technique tries to make the seams between the input images invisible. The basic idea is that image features should be blended across a transition zone proportional in size to the spatial frequency of the features. For example, objects like trees and windowpanes have rapid changes in color. By blending these features in a narrow zone, you will not be able to see the seam because the eye already expects to see color changes at the edge of these features. Clouds and sky are the opposite. These features have to be blended across a wide transition zone because any sudden change in color will be immediately noticeable.

Enblend expects each input TIFF to have an alpha channel. The alpha channel should indicate the region of the file that has valid image data. Enblend compares the alpha regions in the input files to find the areas where images overlap. Alpha channels can be used to indicate to Enblend that certain portions of an input image should not contribute to the final image.

Enblend does not align images for you. Use a tool like Hugin or PanoTools to do this. The TIFFs produced by these programs are exactly what enblend is designed to work with. Sometimes these GUIs allow you to select feathering for the edges of your images. This treatment is detrimental to Enblend. Turn off feathering by deselecting it or setting the feather width to zero.

Enblend blends the images in the order you specify on the command line. You should order your images according to the way that they overlap, for example from left-to-right across the panorama. If you are making a multi-row panorama, I recommend blending each horizontal row individually, and then running Enblend a final time to blend all of the rows together vertically.

COMMON OPTIONS

-a

Pre-assemble non-overlapping images before each blending iteration. This overrides the default behavior which is to blend the images sequentially in the order given on the command line. Enblend will do fewer blending iterations, but it will do more work in each iteration.

-h

Print information on the available options.

-l num

Use exactly this many levels for pyramid blending. This trades off quality of results for faster execution time and lower memory usage. The default is to use as many levels as possible given the size of the overlap region. Enblend may still use a smaller number of levels if the geometry of the images demands it.

-o output-file

Required. Specify the name of the output file.

-v

Verbose output.

-w

Blend around the -180/+180 boundary. Useful for full-360 panoramas. Enblend currently does not blend the zenith or the nadir, so you may still see some seams in these areas.

-z

Use LZW compression for the output images.

input-files

Two or more TIFF files.

EXTENDED OPTIONS

-b kilobytes

Set the block size for Enblend's image cache. This is the amount of data that Enblend will move to and from the disk in one go. The default is 2 MiB which should be good for most systems.

-c

Use the CIE L*a*b* color space for blending.

-g

Gimp (ver. < 2) and Cinepaint exhibit unusual behaviors when loading images with unassociated alpha channels. Use the -g flag to work around this. With this flag Enblend will create the output image with the associated alpha tag set, even though the image is really unassociated alpha.

-f WIDTHxHEIGHT

Set the size of the output image manually. This is useful when the input images are cropped TIFF files, such as those produced by Nona.

-m megabytes

Set the size of Enblend's image cache. This is the amount of memory Enblend will use for storing image data before swapping to disk. The default is 1 GiB.

ADDITIONAL INFORMATION

Please see the Enblend web page at:

http://enblend.sourceforge.net/

AUTHOR

Andrew Mihal <acmihal@users.sourceforge.net>