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Hi,

I'm trying to convert some graphs generated by SVG::TT::Graph to PNG,
using Image::Magick. However, I'm getting empty .png files back,
instead of PNG images.

This is the code I am using:


sub output {
my $self = shift;
my $outdir = $self->{OutDir};
die "No output directory set." unless $self->{OutDir};
my $tempdir = tempdir;
foreach my $graph( keys %{$self->{Graphs}} ) {
my $svg = $self->{Graphs}->{$graph};
print "converting $graph, using tempdir $tempdir\n";
open(my $fh,">","$tempdir/$graph.svg") or die "$!";
print $fh $svg;
close $fh;
open(FH,"<","$tempdir/$graph.svg") or die "$!";
my $image = Image::Magick->new(magick => 'svg');
$image->Read( file => \*FH );
close FH;
my $out_filename = "$graph.png";
chdir $outdir;
open(IMG_FILE,">","$graph.png") or die "$!";
$image->Write( { file => \*IMG_FILE,
filename => "$graph.png",
magick => 'png' });
close IMG_FILE;
}
}

(Note, I am using bareword filehandles because I thought it might make a
difference with an older module like Image::Magick. It doesn't work with
lexical handles either.)

A separate script that takes just a filename from the command line works
just fine:

#!/usr/bin/perl

use warnings;
use strict;

use Image::Magick;

my $infile=shift;

my ($basename,$filetype)=split(/\./,$infile);

open(INFILE,"<",$infile) or die "$!";

my $image=Image::Magick->new;
$image->Read(file=>\*INFILE);
$image->Set(density=>'300x300');
my $outfile=$basename . ".png";
open(OUTFILE,">",$outfile);
$image->Write(file=>\*OUTFILE, filename=>$outfile);

close(INFILE);
close(OUTFILE);

What is the difference I am overlooking here? Or should I just switch to
Image::LibRSVG?

Mart

--
"We will need a longer wall when the revolution comes."
--- AJS, quoting an uncertain source.

On Sun, 18 Oct 2009 15:49:48 +0200, Mart van de Wege <> wrote:

>Hi,
>
>I'm trying to convert some graphs generated by SVG::TT::Graph to PNG,
>using Image::Magick. However, I'm getting empty .png files back,
>instead of PNG images.
>
>This is the code I am using:
>
>
>sub output {
> my $self = shift;
> my $outdir = $self->{OutDir};
> die "No output directory set." unless $self->{OutDir};
> my $tempdir = tempdir;
> foreach my $graph( keys %{$self->{Graphs}} ) {
> my $svg = $self->{Graphs}->{$graph};
> print "converting $graph, using tempdir $tempdir\n";
> open(my $fh,">","$tempdir/$graph.svg") or die "$!";
^^^
I would try binmode($fh) here.
And examine the svg file.

> print $fh $svg;
> close $fh;

Otherwise for a test, starting here, hardcode a
known svg file and do the conversion to png
like you did with the script below.

> open(FH,"<","$tempdir/$graph.svg") or die "$!";
> my $image = Image::Magick->new(magick => 'svg');
^^
sets the object type?
The one Read file example doesen't set the object type
when reading from a filehandle, nor does it put it into binmode FH.
Try what works from the script below, change one thing at a time after
it starts working.

> $image->Read( file => \*FH );
^^
check return value
And its funny Read() does not allow the exact same
parameters available to setAttribute. Write, new, etc..
all have them available.

> close FH;
> my $out_filename = "$graph.png";
> chdir $outdir;
> open(IMG_FILE,">","$graph.png") or die "$!";
> $image->Write( { file => \*IMG_FILE,
^^
check return value
> filename => "$graph.png",
> magick => 'png' });
^^
This is suspicious here, is magick setting the
object attribute, or a help so that the module will
know what output type you really mean, just incase
it doesen't know how to parse filename => "$graph.png"

> close IMG_FILE;

For the test, return from the sub here.

> }
>}
>
>(Note, I am using bareword filehandles because I thought it might make a
>difference with an older module like Image::Magick. It doesn't work with
>lexical handles either.)
>
>A separate script that takes just a filename from the command line works
>just fine:
>
>#!/usr/bin/perl
>
>use warnings;
>use strict;
>
>use Image::Magick;
>
>my $infile=shift;
>
>my ($basename,$filetype)=split(/\./,$infile);
>
>open(INFILE,"<",$infile) or die "$!";
>
>my $image=Image::Magick->new;
>$image->Read(file=>\*INFILE);
>$image->Set(density=>'300x300');
>my $outfile=$basename . ".png";
>open(OUTFILE,">",$outfile);
>$image->Write(file=>\*OUTFILE, filename=>$outfile);
>
>close(INFILE);
>close(OUTFILE);
>
>What is the difference I am overlooking here? Or should I just switch to
>Image::LibRSVG?
>
>Mart

Good luck.
-sln

writes:

> On Sun, 18 Oct 2009 15:49:48 +0200, Mart van de Wege <> wrote:
>
>>Hi,
>>
>>I'm trying to convert some graphs generated by SVG::TT::Graph to PNG,
>>using Image::Magick. However, I'm getting empty .png files back,
>>instead of PNG images.
>>
>>This is the code I am using:
>>
>>
>>sub output {
>> my $self = shift;
>> my $outdir = $self->{OutDir};
>> die "No output directory set." unless $self->{OutDir};
>> my $tempdir = tempdir;
>> foreach my $graph( keys %{$self->{Graphs}} ) {
>> my $svg = $self->{Graphs}->{$graph};
>> print "converting $graph, using tempdir $tempdir\n";
>> open(my $fh,">","$tempdir/$graph.svg") or die "$!";
> ^^^
> I would try binmode($fh) here.
> And examine the svg file.
>
The SVG files are fine. Note that I don't pass the { CLEANUP => 1 }
option to tempdir, so I can examine the intermediate output.

>> print $fh $svg;
>> close $fh;
>
> Otherwise for a test, starting here, hardcode a
> known svg file and do the conversion to png
> like you did with the script below.
>
>> open(FH,"<","$tempdir/$graph.svg") or die "$!";
>> my $image = Image::Magick->new(magick => 'svg');
> ^^
> sets the object type?
> The one Read file example doesen't set the object type
> when reading from a filehandle, nor does it put it into binmode FH.
> Try what works from the script below, change one thing at a time after
> it starts working.

Actually, I tried it without setting magick. Didn't work either.

However, I'll try and take your suggestions into account and hack on the
script some more, adding some debugging print statements.

Mart

--
"We will need a longer wall when the revolution comes."
--- AJS, quoting an uncertain source.

David Harmon <> writes:

> On Sun, 18 Oct 2009 15:49:48 +0200 in comp.lang.perl.misc, Mart van de
> Wege <> wrote,
>>I'm trying to convert some graphs generated by SVG::TT::Graph to PNG,
>>using Image::Magick. However, I'm getting empty .png files back,
>>instead of PNG images.
>
> Start with something simple
>
> use Image::Magick;
> my $img = Image::Magick->new;
> my $x = $img->Read("20080428.gif");
> die "$x" if $x;
> $x = $img->Write("x.png");
> die "$x" if $x;

Well, I broke out the conversion from the main loop, just dumped all the
svg files in one dir, and then ran a loop over those files to convert
them.

That appears to work just fine. I'll see if I can find what went wrong
at first, but for now I can continue working on my module.

Mart

--
"We will need a longer wall when the revolution comes."
--- AJS, quoting an uncertain source.