105 lines
3.6 KiB
Groff
105 lines
3.6 KiB
Groff
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.TH IM_LRMOSAIC 3 "13 May 1991"
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.SH NAME
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im_lrmosaic, im_tbmosaic \- mosaic two images using a zero order procedure
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.SH SYNOPSIS
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#include <vips/vips.h>
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int
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.br
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im_lrmosaic( IMAGE *ref, IMAGE *sec, IMAGE *out,
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.br
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int bandno,
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.br
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int xref, int yref, int xsec, int ysec,
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.br
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int halfcorrelation, int halfarea,
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.br
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int balancetype,
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.br
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int mwidth )
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int
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.br
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im_tbmosaic( IMAGE *ref, IMAGE *sec, IMAGE *out,
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.br
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int bandno,
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.br
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int xref, int yref, int xsec, int ysec,
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.br
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int halfcorrelation, int halfarea,
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.br
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int balancetype,
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.br
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int mwidth )
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.SH DESCRIPTION
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im_lrmosaic() and im_tbmosaic() are used to mosaic two images (left-right and
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top-bottom respectively). Both input images are held by the IMAGE descriptors
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reference and secondary whereas the output is written on the IMAGE descriptor
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out.
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In order to carry out mosaicing, the coordinates of one tie point are
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required. The tie point is expected to be in the overlapping area and has
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coordinates (xref, yref) on the reference image and (xsec, ysec) on the
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secondary image. The tie-point is not used as a start point for the search,
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but is used to specify the overlap of the two images.
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The functions split the overlap area into three parts (top, middle and bottom;
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or left, middle and right) and search the reference image in each part for the
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20 best high contrast points. These 60 points are then searched for in the
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secondary image, giving a set of 60 possible corrected vectors.
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A straight line is fitted through the 60 vectors, and points discarded which
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lie a significant distance from the line. The line is then refitted to the
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remaining points, and the process repeated until either all remaining points
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lie on a straight line, or too many points have been discarded.
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If a good straight line fit is found, ref and sec are joined. If no fit was
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found, the functions fail with an error message. Note that these functions
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detect rotation: if the straight line found requires sec to be rotated, they
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also fail with an error message.
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Each function requires three more parameters:
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halfcorrelationsize - sets the size of the fragments of ref
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for which the function searches sec. The actual window
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will be of size 2*halfcorrelationsize+1. We recommend a
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value of 5.
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halfareasize - sets the size of the area of sec that is
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searched. The actual area searched will be of size
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2*halfareasize+1. We recommend a value of 14.
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balancetype - sets the style of the balancing the functions
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perform. Balancing finds the average value of pixels in
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the overlap area, and scales the left and right images
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(or top and bottom images) so as to make the images
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match in average overlap. Possible values are:
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0 - means do no balancing.
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1 - means keep the left image unadjusted and adjust
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the contrast of the right image to match the left.
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2 - means keep the right image unadjusted and scale
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the left image to match it.
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3 - means adjust the contrast of both the left and
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right images to bring both averages to a middle
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value. The middle value chosen is weighted by the
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number of pixels in each image: large images will be
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adjusted less than small images.
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Balancing is useful for mosaicing frames from photographic or video sources
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where exact colour control is impossible and exposure varies from frame to
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frame. Balancing is only allowed for uncoded uchar images.
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The final "mwidth" parameter sets the maximum blend width, see im_lrmerge(3).
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See also im_global_balance() for a better way of balancing large mosaics.
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.SH RETURN VALUE
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All functions return 0 on success and -1 on error.
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.SH SEE ALSO
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im_lrmerge(3), im_tbmerge(3), im_global_balance(3).
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