How to draw 2D diagram in linux

Question

I have a .txt file contatning points which is look like following:

##x1 y1 x2 y2
123 567 798 900
788 900 87  89
....

I want to draw 2D diagram

Answer 1

You can also do this using rsvg-convert (from librsvg) or svg2png. Both of those programs expect an inout file in SVG format and render it as a PNG file. So you would need to convert your

123 567 798 900
788 900 87  89

into this type of thing

<svg xmlns="http://www.w3.org/2000/svg" version="1.1">
  <line x1="123" y1="567" x2="798" y2="900" stroke="blue" stroke-width="1"/>
  <line x1="788" y1="900" x2="87" y2="89" stroke="blue" stroke-width="1"/>
</svg>

That can be done easily enough with a little awk script like this:

awk '
   BEGIN{ printf("<svg xmlns=\"http://www.w3.org/2000/svg\" version=\"1.1\">\n") }

  {
     x1=$1; y1=$2; x2=$3; y2=$4;
     printf("<line x1=\"" x1 "\" y1=\"" y1 "\" x2=\"" x2 "\" y2=\"" y2 "\" stroke=\"blue\" stroke-width=\"1\"/>\n")
  }

  END{ printf("</svg>\n") }' points.txt

You can then pump the output of that into either of the two programs I mentioned above:

awk ... | rsvg-convert -b \#ffff00 > result.png

Answer 2

Updated

In the light of your reply about the number of lines and the maximum x,y dimensions, my original, ImageMagick-based approach at the bottom of this answer is clearly NOT the right one for your specific problem. However, I will leave it for others to see as it would be perfectly fine for up to a few dozen lines. I am now providing a more appropriate gnuplot version.

Gnuplot Version

If you want to do it with gnuplot, it would look something like this:

set terminal png size 1000,1000
set output 'result.png'
unset xtics
unset ytics
unset border
plot 'lines.txt' using 1:2:($3-$1):($4-$2) with vectors nohead notitle

If you save that in a file calle plot.cmd, you can then run it with

gnuplot < plot.cmd

If you want arrowheads, use a variant like this:

set terminal png size 1000,1000
set output 'result.png'
set style arrow 1 heads filled size screen 0.03,15,45 ls 1
unset xtics
unset ytics
unset border
plot 'lines.txt' using 1:2:($3-$1):($4-$2) with vectors arrowstyle 1  notitle 

Magick++ and C++ Answer

I decided to work out a Magick++ and C++ answer, just for fun. The code looks like this - and the command to compile is shown in the comments at the top.

////////////////////////////////////////////////////////////////////////////////
// sample.cpp
// Mark Setchell
//
// ImageMagick Magick++ sample code
//
// Compile with:
// g++ sample.cpp -o sample $(Magick++-config --cppflags --cxxflags --ldflags --libs)
////////////////////////////////////////////////////////////////////////////////
#include <Magick++.h> 
#include <iostream> 
#include <fstream>
#include <sstream>
#include <string>
#include <vector>

using namespace std; 
using namespace Magick; 

int main(int argc,char **argv) 
{ 
   InitializeMagick(*argv);

   // Create an image object, scaled by a factor of 100 to speed it up !
   float scale=100.0;
   Image image("650x650","white");

   // Construct drawing list 
   std::list<Magick::Drawable> drawList;

   // Initial settings, blue lines 1 pixel thick
   drawList.push_back(DrawableStrokeColor("blue"));
   drawList.push_back(DrawableStrokeWidth(1));

   // Read in lines from file, expected format "x1 y1 x2 y2"
   int lineno=0;
   std::ifstream infile("lines.txt");
   std::string line;
   while (std::getline(infile, line))
   {
      std::istringstream iss(line);
      int x1,y1,x2,y2;
      iss >> x1;
      iss >> y1;
      iss >> x2;
      iss >> y2;
      x1 = int(x1/scale);
      y1 = int(x2/scale);
      x2 = int(y1/scale);
      y2 = int(y2/scale);
      cout << "Line: " << ++lineno << " " << x1 << "," << y1 << " " << x2 << "," << y2 << endl;
      // Add this point to the list of lines to draw
      drawList.push_back(DrawableLine(x1,y1,x2,y2));
   }

   // Draw everything using completed drawing list 
   image.draw(drawList);

   // Write the image to a file 
   image.write( "result.png" ); 

   return 0; 
}

I generated 1,000 lines of random test data with Perl like this:

perl -E 'for($i=0;$i<1000;$i++){printf("%d %d %d %d\n",int rand 65000,int rand 65000, int rand 65000, int rand 65000);}' > lines.txt

The result looks like this:

Original Answer

You could also do it quite easily with ImageMagick which is already installed on most Linux distros anyway. There are actually only 4 lines of code in the following - the rest is all comments:

#!/bin/bash

# Create the output image, 1000x1000 pixels say
convert -size 1000x1000 xc:pink result.png

# Suppressing lines that have a hash (#) at the start, read in the file "lines.txt"
grep -v "^#" lines.txt | while read x1 y1 x2 y2; do

   echo Read line $x1,$y1 $x2,$y2

   # Tell ImageMagick to draw the line on the image
   convert result.png -stroke blue -strokewidth 5 -draw "line $x1,$y1 $x2,$y2" result.png
done

Output

Read line 123,567 798,900
Read line 788,900 87,89