GRASS GIS 7 Programmer's Manual
7.9.dev(2021)-e5379bbd7
inside.c
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/*
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****************************************************************************
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*
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* MODULE: Vector library
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*
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* AUTHOR(S): Original author CERL, probably Dave Gerdes.
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* Update to GRASS 5.7 Radim Blazek.
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*
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* PURPOSE: Lower level functions for reading/writing/manipulating vectors.
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*
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* COPYRIGHT: (C) 2001 by the GRASS Development Team
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*
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* This program is free software under the GNU General Public
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* License (>=v2). Read the file COPYING that comes with GRASS
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* for details.
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*
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*****************************************************************************/
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#include <
grass/vector.h
>
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double
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dig_x_intersect
(
double
beg_x,
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double
end_x,
double
beg_y,
double
end_y,
double
Y
)
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{
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double
b
;
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/* assumes beg_y != end_y */
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/* sort for numerical stability */
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if
(end_x < beg_x || (end_x == beg_x && end_y < beg_y)) {
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b = end_x;
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end_x = beg_x;
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beg_x =
b
;
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b = end_y;
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end_y = beg_y;
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beg_y =
b
;
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}
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/* solve simple linear equation to get X = a + b * Y
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* with
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* b = (end_x - beg_x) / (end_y - beg_y)
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* a = beg_x - b * beg_y
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*
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* simplify a + b * Y:
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* a + b * Y = beg_x - b * beg_y + b * Y
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* a + b * Y = beg_x + b * (Y - beg_y) */
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b = (end_x - beg_x) / (end_y - beg_y);
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return
beg_x + b * (Y - beg_y);
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}
dig_x_intersect
double dig_x_intersect(double beg_x, double end_x, double beg_y, double end_y, double Y)
Definition:
inside.c:21
b
double b
Definition:
r_raster.c:39
Y
#define Y
Definition:
ogsf.h:138
vector.h
lib
vector
diglib
inside.c
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