107 lines
3.2 KiB
Groff
107 lines
3.2 KiB
Groff
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.TH IM_COMPASS 3 "2 May 1991"
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.SH NAME
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im_compass, im_rank_image, im_maxvalue, im_lindetect, im_gradient \- extract features from an image with
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a rotating input mask
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.SH SYNOPSIS
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#include <vips/vips.h>
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int im_rank_image(in, out, n, index)
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.br
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IMAGE **in;
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.br
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IMAGE *out;
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.br
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int n;
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.br
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int index;
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int im_maxvalue(in, out, n)
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.br
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IMAGE **in;
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.br
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IMAGE *out;
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.br
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int n;
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int im_compass(in, out, mask)
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.br
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IMAGE *in, *out;
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.br
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INTMASK *mask;
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int im_lindetect(in, out, mask)
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.br
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IMAGE *in, *out;
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.br
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INTMASK *mask;
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int im_gradient(in, out, mask)
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.br
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IMAGE *in, *out;
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.br
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INTMASK *mask;
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.SH DESCRIPTION
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.B im_rank_image()
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sorts the input images pixel-wise, then outputs an image in which each pixel
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is selected from the sorted list by the
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.B index
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parameter. For example, if
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.B index
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is zero, then each output pixel will be the minimum of all the corresponding
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input pixels.
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It works for any uncoded, non-complex
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image type. All input images must match in size, format, and number of bands.
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These functions convolve the image pointed by the image descriptor in with the
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mask pointed by mask and put the result in the image pointed by out.
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The mask structure INTMASK is returned by the function im_read_imask(3), for
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integer mask only. Input should be unsigned char; processing is carried out
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using look-up tables. The output is integer. coefficients. The size of the
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output image and the number of channels are the same as the corresponding of
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the input.
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If the sizes of the mask are xm and ym and the sizes of the image are xs and ys,
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then there is a black border at the output image as follows:
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The top ym/2 lines black, bottom ys-ym/2-ym lines black; each of the remaining
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lines has the initial xm/2 pels blank, and the final
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xs-xm/2-xm pels black (division over 2 is integer division).
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The output at each point is divided by scale and then the offset is added.
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Both offset and scale are held in mask.
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.B im_maxvalue()
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is a convenience function: it is simply:
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im_rank_image( in, out, n, n - 1 )
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.B im_compass()
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convolves each point of the input byte image pointed by in with 8 masks.
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The first mask is the entered mask and the seven remaining masks are produced
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by successive rotations of the entered mask by 45 degrees. The maximum output
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of all masks at each point is written to the output integer IMAGE descriptor.
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The function expects as input a square mask of odd size.
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.B im_lindetect()
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convolves each point of the input byte image pointed by in with 4 masks.
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The first mask is the entered mask and the three remaining masks are produced
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by successive rotations of the entered mask by 45 degrees. The maximum output
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of all masks at each point is written to the output integer IMAGE descriptor.
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The function expects as input a square mask of odd size.
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.B im_gradient()
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convolves each point of the input byte image pointed by in with 2 masks;
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the entered mask and with a 90 degrees rotation of the
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entered mask. If g1, g2 are the result of each convolution then for each point
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abs(g1) + abs(g2) is written to the output integer IMAGE descriptor.
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The function expects as input a square mask of any size.
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.SH RETURN VALUE
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All functions returns 0 on success and -1 on error.
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.SH SEE\ ALSO
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im_readmask(3), im_conv(3).
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.SH COPYRIGHT
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.br
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N. Dessipris
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.SH AUTHOR
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N. Dessipris \- 02/05/1991
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