54 lines
2.2 KiB
Groff
54 lines
2.2 KiB
Groff
.TH IM_GLOBAL_BALANCE 3 "13 May 1991"
|
|
.SH NAME
|
|
im_global_balance, im_global_balancef \- perform global mosaic balancing on
|
|
an image
|
|
.SH SYNOPSIS
|
|
#include <vips/vips.h>
|
|
|
|
int
|
|
.br
|
|
im_global_balance( IMAGE *in, IMAGE *out, double gamma )
|
|
|
|
int
|
|
.br
|
|
im_global_balance_float( IMAGE *in, IMAGE *out, double gamma )
|
|
|
|
.SH DESCRIPTION
|
|
These functions takes an image assembled with the mosaicing functions
|
|
(im_*merge*(), im_*mosaic*()), take it apart, and reassemble it, globally
|
|
optimising the image balance. This is useful for assembling image mosaics
|
|
from sources where the exposure is uncontrolled and may vary from tile to tile
|
|
--- such as video, or photographic sources.
|
|
|
|
The function finds a set of factors, one for each of the input images, and
|
|
scales each image by its factor before reassembling. The factors are chosen so
|
|
as to minimise the average grey-level difference between neighboring images at
|
|
their overlaps. Trivial overlaps (where the width and height of the overlap
|
|
are both less than 20 pixels) are ignored.
|
|
|
|
The gamma parameter is the gamma of the image input system. It is used during
|
|
brightness adjustment. Set to 1.0 to disable gamma, to 1.6 for a typical IR
|
|
vidicon camera, or 2.3 for a typical video camera.
|
|
|
|
It relies on information left by the mosaicing functions in ".desc" files. If
|
|
the ".desc" file of the input image has been corrupted, or is strangely
|
|
complicated, or if any of the original input images have been moved or
|
|
deleted, the function can fail.
|
|
|
|
The function will fail for mosaics larger than about 7 by 7 frames, since it
|
|
will run out of file descriptors (UNIX sets a limit of 256 per process). To
|
|
balance larger mosaics, just assemble them in 7x7 sections, balancing and
|
|
saving each part in turn, before loading, assembling and balancing the final
|
|
image. The function can also fail if there are significant mosaicing errors.
|
|
|
|
im_global_balancef() works as im_global_balance(), but outputs a float
|
|
rather than a uchar image. This lets you adjust the range of the image
|
|
manually, if the automatically-found scales are causing burn-out.
|
|
|
|
.SH RETURN VALUE
|
|
All functions return 0 on success and -1 on error.
|
|
.SH SEE ALSO
|
|
im_lrmerge(3), im_lrmosaic(3).
|
|
.SH COPYRIGHT
|
|
Birkbeck College and the National Gallery, 1991 - 1995.
|