66 lines
1.8 KiB
Groff
66 lines
1.8 KiB
Groff
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.TH MACROS 3 "11 April 1990"
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.SH NAME
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IM_REGION_ADDR,
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IM_REGION_LSKIP,
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IM_REGION_N_ELEMENTS, IM_REGION_SIZEOF_LINE \-
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macros for regions
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.SH SYNOPSIS
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.B #include <vips/vips.h>
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.br
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.B #include <vips/region.h>
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int IM_REGION_LSKIP( reg )
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.br
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REGION *reg;
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int IM_REGION_N_ELEMENTS( reg )
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.br
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REGION *reg;
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int IM_REGION_SIZEOF_LINE( reg )
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.br
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REGION *reg;
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char *IM_REGION_ADDR( 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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.SH DESCRIPTION
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These macros help to simplify address arithmetic for regions.
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IM_REGION_LSKIP(3) returns the number of *bytes* you should add to move
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down a scan line. Remember that if your pointer has been cast to the type
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of the image pels, this will not be the correct amount to add! The value
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lskip returns can be changed by a call to im_prepare(3).
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IM_REGION_N_ELEMENTS(3) returns the number of band elements across the region.
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IM_REGION_SIZEOF_LINE(3) returns sizeof( horizontal line across region ).
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IM_REGION_ADDR(3) returns a pointer to the pixel at position (x,y) in the
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image on which reg has been defined. The point (x,y) should lie within the
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valid area for this region.
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If the macro DEBUG has been defined, then IM_REGION_ADDR(3) will also
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perform bounds checking. If you ask for the address of a pel outside the rect
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reg->valid, then IM_REGION_ADDR(3) will print an error message of the form:
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IM_REGION_ADDR: point out of bounds, file "test.c", line 18
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(point x=50, y=0
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should have been within Rect left=0, top=0, width=50, height=50)
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and call abort(3).
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DEBUG needs to be defined *before* region.h is included. Either define DEBUG
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with -D in your Makefile, or have a #define DEBUG right at the top of your
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file.
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.SH COPYRIGHT
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National Gallery, 1993
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.SH SEE ALSO
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im_malloc(3), im_open_local(3).
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.SH AUTHOR
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J. Cupitt \- 23/7/93
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