Creating Heat Map in perl

[huzefa52]

can anybody please help me in creating heat map in perl. I have tried using Imager::Heatmap library, but i am not getting it. I am a newbie.

[nevdka]

I haven't used that module, but you will likely get better responses if you show the code you have tried, and tell us where it's not doing what you want it to do.

Oh, and put the code inside <code></code> tags, or some of the monks will get grumpy.

[huzefa52]

Hi, Thanks for the reply, I am using below code, it is giving me following error. Can't locate object method "Imager=HASH(0xfeeb4d0)" via package "Imager::Heatmap" at heatmap.pl line 28.

#!/usr/bin/perl -w
use strict;
#use warnings;
use utf8;
use XSLoader;
use Carp;
use Imager;
use List::Util qw/ max /;
use Imager;
use Imager::Heatmap;
my $hmap = Imager::Heatmap->new(
    xsize  => 640,        # Image width
    ysize  => 480,        # Image height
    xsigma => 10,         # Sigma value of X-direction
    ysigma => 10,         # Sigma value of Y-direction
);
 
my @piont_datas = ( [ 10, 20, 50 ], [ 20, 40, 70 ] );
# Add point datas to construct density matrix
$hmap->insert_datas(@piont_datas); # @point_datas should be: ( [ x1, y
+1, weight1 ], [ x2, y2, weight2 ] ... )
 
#$hmap->insert_datas(...); # You can call multiple times to add large 
+data that cannot process at a time.
 
# After adding datas, you could get heatmap as Imager instance.
my $img = $hmap->draw;
 
# Returned image is 4-channels image. So you can overlay it on other i
+mages.
my $base_img->rubthrough( src => $hmap->$img );  # Overlay on other im
+ages(see Imager::Transformations)

$img = Imager->new(
        xsize    => $hmap->xsize,
        ysize    => $hmap->ysize,
        channels => 4,
    );
# And you can access probability density matrix using matrix method if
+ you like.
# In case, maybe you would like to create some graduations which be as
+signed to color of heatmap and its value.
$hmap->matrix;

[Corion]

So, what is in line 28? Have you looked at it and checked it that it means what you intend?

my $base_img->rubthrough( src => $hmap->$img );  # Overlay on other im
+ages(see Imager::Transformations)

Please explain for every item in English what it is supposed to mean. Especially, explain the construct $hmap->$img.

[space_monk]

Very minor thing s/piont_datas/point_datas/g;. The only reason the code doesn't generate an error is because you made this spelling mistake consistently.
What is the last line doing? $hmap->matrix simply returns a reference to the density matrix - on its own it does nothing.

[Mr. Muskrat]

The synopsis for Imager::Heatmap can not be run as is. It doesn't create $base_img, it doesn't show how to properly use matrix, etc. So it is no surprise that what you ended up with didn't work.

Try this as a starting point. It uses your data and creates a png file in the current directory.

#!/bin/env perl
use strict;
use warnings;

use Imager::Heatmap;

my $hmap = Imager::Heatmap->new(
    xsize  => 640,        # Image width
    ysize  => 480,        # Image height
    xsigma => 10,         # Sigma value of X-direction
    ysigma => 10,         # Sigma value of Y-direction
);

# @point_datas should be: ( [ x1, y1, weight1 ], [ x2, y2, weight2 ] .
+.. )
my @point_datas = ( [ 10, 20, 50 ], [ 20, 40, 70 ] );

# Add point datas to construct density matrix
$hmap->insert_datas(@point_datas); 

# After adding datas, get heatmap as Imager instance.
my $img = $hmap->draw;

# create png file in current directory
$img->write( file => './hm.png' );

Here's the generated heatmap image.