118 lines
3.2 KiB
Groff
118 lines
3.2 KiB
Groff
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.TH REGION-OPERATIONS 3 "11 April 1990"
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.SH NAME
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im_region_buffer, im_region_image, im_region_region, im_region_position,
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im_region_equalsregion \-
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attach data to region
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.SH SYNOPSIS
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.B #include <vips/vips.h>
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int im_region_buffer( reg, r )
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.br
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REGION *reg;
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.br
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Rect *r;
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int im_region_image( reg, r )
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.br
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REGION *reg;
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.br
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Rect *r;
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int im_region_region( reg, treg, r, x, y )
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.br
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REGION *reg, treg;
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.br
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Rect *r;
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.br
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int x, y;
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int im_region_position( reg, x, y )
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.br
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REGION *reg;
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.br
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int x, y;
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int im_region_equalsregion( REGION *reg1, REGION *reg2 )
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.SH DESCRIPTION
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These functions are used to say where exactly input from or output to a
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region goes. Briefly,
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.B im_region_buffer(3)
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gives a region its own piece of local storage,
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.B im_region_image(3)
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links the region to an image, and
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.B im_region_region(3)
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links the region to another region.
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.B im_region_region(3)
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is the most powerful of the three --- you can use it to
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avoid copy operations. See the source for
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.B im_extract(3),
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.B im_insert(3),
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.B im_copy(3),
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.B im_embed(3),
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and
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.B im_lrmerge(3)
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for examples of its use, and see also
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.B im_prepare_copy(3).
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.B im_region_buffer(3)
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clips Rect r against the size of the image upon which reg is
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defined, then searches for any calculated pixels which enclose that area. If
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there are any suitable pixels already, the region is set to point to them.
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Otherwise, a fresh buffer is allocated.
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If region->buffer->done is set, then the region is already calculated.
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Otherwise, the pixels need to be calculated.
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.B im_region_buffer(3)
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is called by
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.B im_prepare(3)
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just before it calls the user generate function.
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.B im_region_image(3)
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attaches reg to the image on which it was defined. The image
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has to be SETBUF, MMAPIN, MMAPINRW, or OPENIN --- ie., the types passed by
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.B im_incheck(3).
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.B im_region_region(3)
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redirects reg to treg. treg can be defined on another
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image. r is clipped against the size of reg's image, and against treg->valid.
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treg has to have pel data associated with it (ie. memory local to treg, memory
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that is part of the image on which treg is defined, or even memory from a
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third region), and the pel data has to be in a form which is compatible with
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reg, ie. BandFmt and Bands must be the same.
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r becomes the valid field in reg, (x,y) is the top left-hand corner of the
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area in treg to which valid is mapped.
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.B im_region_position(3)
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changes reg->valid, so that reg->valid.left == x and
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reg->valid.top == y. width and height are clipped against the size of the
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image. If x < 0 or y < 0 or the clipped rect has zero width or height, the
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call fails.
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This function affects the way that pels are addressed by the
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.B IM_REGION_ADDR(3)
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macro. It does not affect the pels themselves! It has the effect of moving
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the area of pels a region represents. This call is used by
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.B im_extract(3).
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.B im_region_equalsregion(3)
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tests for reg1 and reg2 are identical, ie.:
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IM_REGION_ADDR( reg1, x, y ) ==
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IM_REGION_ADDR( reg2, x, y ) &&
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*IM_REGION_ADDR( reg1, x, y ) ==
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*IM_REGION_ADDR( reg2, x, y )
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It is used internally by VIPS, but may be useful to applications.
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.SH RETURN VALUE
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All int-valued functions return zero on success and non-zero on error.
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.SH COPYRIGHT
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National Gallery, 1993
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.SH AUTHOR
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J. Cupitt \- 23/7/93
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