How to get plt file's printable area

Plt file is described by HPGL, which is the primary printer control language used by Hewlett-Packard plotters. Sometimes we want to get the printable area of a PLT file, how to do it?

 

My solution is to extract the coordinates in PLT file and find out the boundary rectangle.

Following is the sample code by C#:

 

 

 

 

string filename = @"C:/Documents/test.PLT";//make sure you have this file

 

 

 

StreamReader sr = new StreamReader(filename);

 

 

 

string input = sr.ReadToEnd();

sr.Close();

 

//use regular expression to extract the coordinates boundary

 

 

 

Regex reg = new Regex("PDPA[//d+,//d+]+;");

 

 

 

MatchCollection matches = reg.Matches(input);

 

 

 

// if following coordinates are divided by 400, the unit will be mm

 

 

 

 

int xMax = 0;

 

 

 

int xMin = 0;

 

 

 

int yMax = 0;

 

 

 

int yMin = 0;

 

 

//find out the coordinates boundary

 

 

 

 

foreach (Match m in matches)

{

 

 

 

//remove 'PDPA'

 

 

 

 

string v = m.Value.Substring(4,m.Value.Length-5);

 

 

 

string[] coords = v.Split(',');

 

 

 

IEnumerable<string> xCoords = coords.Where((s, i) => i%2 == 0);

 

 

 

IEnumerable<string> yCoords = coords.Where((s, i) => i % 2 != 0);

 

 

 

 

int LocalXMax = xCoords.Max((s)=>Int32.Parse(s));

 

 

 

int LocalXMin = xCoords.Min((s) => Int32.Parse(s));

 

 

 

int LocalYMax = yCoords.Max((s) => Int32.Parse(s));

 

 

 

int LocalYMin = yCoords.Min((s) => Int32.Parse(s));

xMax = xMax >= LocalXMax ? xMax : LocalXMax;

xMin = xMin <= LocalXMin ? xMin : LocalXMin;

yMax = yMax >= LocalYMax ? yMax : LocalYMax;

yMin = yMin <= LocalYMax ? yMin : LocalYMin;

}

 

//draw the boundary

 

 

 

string outFileName = filename + "out.plt";

 

 

 

string pt1 = "PA" + xMin +"," + yMin + ";";

 

 

 

string pt2 = "PA" + xMin + "," + yMax + ";";

 

 

 

string pt3 = "PA" + xMax + "," + yMax + ";";

 

 

 

string pt4 = "PA" + xMax + "," + yMin + ";";

 

 

 

string appendingText = pt1 + "PD;" + pt2 + pt3 + pt4 + pt1 + "PU;SP;PG1";

 

 

 

string text = input.Replace("PG1",appendingText);

 

 

 

StreamWriter sw = new StreamWriter(outFileName);

 

sw.Write(text);

sw.Flush();

sw.Close();