projection

projection_pl ( : : Row, Column, Row1, Column1, Row2, Column2 : RowProj, ColProj )

Calculate the projection of a point onto a line.

The operator projection_pl calculates the projection of a point (Row,Column) onto a line which is represented by the two points (Row1,Column1) and (Row2,Column2). The coordinates of the projected point are returned in RowProj and ColProj.

Parameters

`Row` (input_control)	point.y(-array) `->` real / integer
Row coordinate of the point.

`Column` (input_control)	point.x(-array) `->` real / integer
Column coordinate of the point.

`Row1` (input_control)	point.y(-array) `->` real / integer
Row coordinate of the first point on the line.

`Column1` (input_control)	point.x(-array) `->` real / integer
Column coordinate of the first point on the line.

`Row2` (input_control)	point.y(-array) `->` real / integer
Row coordinate of the second point on the line.

`Column2` (input_control)	point.x(-array) `->` real / integer
Column coordinate of the second point on the line.

`RowProj` (output_control)	number(-array) `->` real
Row coordinate of the projected point.

`ColProj` (output_control)	number(-array) `->` real
Column coordinate of the projected point

Example

dev_set_color ('black')
RowLine1 := 400
ColLine1 := 200
RowLine2 := 240
ColLine2 := 400
Rows := 300
Columns := 50
disp_line (WindowHandle, RowLine1, ColLine1, RowLine2, ColLine2)
n := 0
for Rows := 40 to 200 by 4
  dev_set_color ('red')
  disp_circle (WindowHandle, Rows+n, Columns, 2)
  projection_pl (Rows+n, Columns, RowLine1, ColLine1, RowLine2, ColLine2,
                 RowProj, ColProj)
  dev_set_color ('blue')
  disp_line (WindowHandle, RowProj-2, ColProj, RowProj+2, ColProj)
  disp_line (WindowHandle, RowProj, ColProj-2, RowProj, ColProj+2)
  n := n+8
endfor

Result

projection_pl returns 2 (H_MSG_TRUE).

Parallelization Information

projection_pl is reentrant and processed without parallelization.

Module

Foundation