150 lines
3.6 KiB
Groff
150 lines
3.6 KiB
Groff
.TH CONVOLUTION 3 "2 May 1991"
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.SH NAME
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im_conv, im_conv_raw, im_convf, im_convf_raw,
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im_convsep, im_convsep_raw, im_convsepf, im_convsepf_raw,
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im_convsub, im_shrink \- convolves an image with a generalised mask
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.SH SYNOPSIS
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#include <vips/vips.h>
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int im_conv(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_conv_raw(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_convf(in, out, mask)
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.br
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IMAGE *in, *out;
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.br
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DOUBLEMASK *mask;
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int im_convf_raw(in, out, mask)
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.br
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IMAGE *in, *out;
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.br
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DOUBLEMASK *mask;
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int im_convsep(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_convsep_raw(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_convsepf(in, out, mask)
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.br
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IMAGE *in, *out;
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.br
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DOUBLEMASK *mask;
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int im_convsepf_raw(in, out, mask)
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.br
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IMAGE *in, *out;
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.br
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DOUBLEMASK *mask;
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int im_convsub(in, out, mask, xskip, yskip)
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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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.br
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int xskip, yskip;
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int im_shrink(in, out, xfactor, yfactor)
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.br
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IMAGE *in, *out;
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.br
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double xfactor, yfactor;
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.SH DESCRIPTION
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These functions
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convolve the image
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.B in
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with the matrix
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.B mask
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and put the result in the image
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.B out.
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Input should be non-complex. The size and type of the output image are
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the same as the size of the input. To output a larger type (for example,
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to output an int image from convolution of a byte image, avoiding clipping),
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cast the input image up with
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.B im_clip2fmt(3).
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The output image is the same size as the input. The edge pixels are calculated
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by expanding the input image using
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.B im_embed(3)
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in mode 1 (replicating edge pixels) just enough so that the output can match
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the input.
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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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The
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.B im_conv*(3)
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functions have 'raw' versions which do not add the border: instead the
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output image is smaller than the input.
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.B im_conv(3)
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and
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.B im_conv_raw(3)
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convolve any non-complex input image to make an output image of the same
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type. Rounding is appropriate to the image type.
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.B im_convf(3)
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and
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.B im_convf_raw(3)
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convolves to float (double if the input is double).
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The function expects a double mask.
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.B im_convsep(3)
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and
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.B im_convsep_raw(3)
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carry out convolution using an 1xN or Nx1 separable mask.
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The function scales the output result by dividing it with scale*scale. The
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scale factor should therefore be the sqrt of the scale of the square NxN mask.
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Rounding is appropriate to the image type. It works on any non-complex image,
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and writes the output in the same format as the input.
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The function expects integer mask.
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.B im_convsepf(3)
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and
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.B im_convsepf_raw(3)
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convolves to float (double if the input is double).
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The function expects a double mask.
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.B im_convsub(3)
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convolves the byte image pointed by in and writes the result as a byte output.
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Using this function the input image is subsampled on
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both directions by an integer factor of xskip horizontally and
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an integer factor of yskip vertically.
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During the covolution, values are rounded before division.
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Both input and output are bytes. Output is clipped between 0 and 255.
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The function expects an integer mask.
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.B im_shrink(3)
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shrink the input image file by xfactor along the horizontal and
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yfactor along the vertical direction. The function does not perform subpixel
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interpolation and therefore the resultant image can present aliasing especially
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for small x and y factors. Any size image, any non-complex type, any number of
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bands.
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.SH RETURN VALUE
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The functions returns 0 on success and -1 on error.
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.SH SEE ALSO
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im_read_imask(3), im_compass(3), im_fastcor(3), im_log_dmask(3),
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im_clip2fmt(3)
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