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 represent by the start point (Row1,Column1) and the end point (Row2,Column2). RowProj is the row of the projection point and ColProj is the column of the projection point.

Parameters

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

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

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

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

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

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

`RowProj` (output_control)	number(-array) `->` real
Row of the projection

`ColProj` (output_control)	number(-array) `->` real
Column of the projection

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

Basic operators