Using ImageMagick effectively

[Aldebaran]

The topic of html templating seems to be trending. I'm always looking to increase what I can do with templates, and an important part of that for my needs is manipulating images. I want to be able to use perl for things that I might otherwise use a command line for, if nothing else than to spare the keystrokes as per the virtue of laziness. But it's essential for me not to have images that are 2 megs instead of 100 k, where most images do fine.

The first problem? I'm on a new machine, and every time I install ImageMagick, I feel like I'm getting hazed. What I think needs to happen is that perl has to be able to find the dev libraries, and somehow, what I have isn't doing that yet. According to my ubuntu 14.04 OS, I have this installed. Yet I can't get past the initial use. I took a couple screenshots and put them up on a page, which I created by commenting out the use statement: screenshots.

$ perl magick1.pl
Can't locate Image/Magick.pm in @INC (you may need to install the Imag
+e::Magick module) (@INC contains: template_stuff /etc/perl /usr/local
+/lib/perl/5.18.2 /usr/local/share/perl/5.18.2 /usr/lib/perl5 /usr/sha
+re/perl5 /usr/lib/perl/5.18 /usr/share/perl/5.18 /usr/local/lib/site_
+perl .) at magick1.pl line 15.
BEGIN failed--compilation aborted at magick1.pl line 15.
$

I don't want to get too ambitious for how much to get done on one thread, but after it's installed, I'd like to use perl to get all images in a directory shrunk to less than 100 k. Thanks for your comment.

[Your Mother]

Also consider GraphicsMagick. A nearly drop-in fork/replacement that is (supposedly) better and saner on the backend in most every way. I know ImageMagick has blown up on me a few times with memory or hanging and such for things that didn't seem reasonable (manipulating a few animated frames, I think). I have no installation advice.

[Anonymous Monk]

According to my ubuntu 14.04 OS, I have this installed.

Do you also have the perlmagick package (http://packages.ubuntu.com/trusty/perlmagick) installed? Is the perl in your PATH the system perl or a custom build?

[Aldebaran]

Installing perlmagick was what I needed. I've written a routine that iterates through the images folder, but I fail to create and assign the object correctly:

sub resize_images  {
use 5.010;
use Path::Class;
use Image::Magick;

my ($rvars) = shift;
my %vars = %$rvars;
opendir my $hh, $vars{to_images} or warn "warn  $!\n";
while (defined ($_ = readdir($hh))){
  my $image = Image::Magick->new;
  $image->ReadImage($_);
  $x = $image->Get('filesize');
  say "$_ has filesize of $x";
}
}

Output:

Screenshot from 2014-08-21 13:10:18.png has filesize of 
Screenshot from 2014-09-25 17:14:08.png has filesize of 
Screenshot from 2014-08-21 13:22:42.png has filesize of 
zbears.jpg has filesize of 
. has filesize of 
.. has filesize of 
yjj.jpg has filesize of

Fishing for tips....

[tangent]

You need to prepend the directory to the filename (see readdir), and you can check if the read was successful:

my $dir = $vars{to_images};
...
my $err = $image->ReadImage("$dir/$_");
warn "$err" if $err;

Also, might be better to filter out the non-image files before passing to Image::Magick.

[trippledubs]

bash# for i in *jpg; do convert "$i" -resize '800x600' "resize-${i}"; 
+done

Alternate solution using the command line. Put an ampersand at the end and you can start scripting while it is converting in the background.

[Aldebaran]

/home/fred/Desktop/root3/pages/giants/template_stuff/aimages/Screensho
+t from 2014-08-21 13:10:18.png has filesize of 250625 bytes or 244.75
+09765625 k
file is /home/fred/Desktop/root3/pages/giants/template_stuff/aimages/S
+creenshot from 2014-08-21 13:10:18.png
ratio is 2.39951937806373
/home/fred/Desktop/root3/pages/giants/template_stuff/aimages/Screensho
+t from 2014-09-25 17:14:08.png has filesize of 166140 bytes or 162.24
+609375 k
file is /home/fred/Desktop/root3/pages/giants/template_stuff/aimages/S
+creenshot from 2014-09-25 17:14:08.png
ratio is 1.59064797794118
/home/fred/Desktop/root3/pages/giants/template_stuff/aimages/Screensho
+t from 2014-08-21 13:22:42.png has filesize of 81126 bytes or 79.2246
+09375 k
/home/fred/Desktop/root3/pages/giants/template_stuff/aimages/zbears.jp
+g has filesize of 872877 bytes or 852.4189453125 k
file is /home/fred/Desktop/root3/pages/giants/template_stuff/aimages/z
+bears.jpg
ratio is 8.35704848345588
/home/fred/Desktop/root3/pages/giants/template_stuff/aimages/. has fil
+esize of  bytes or 0 k
/home/fred/Desktop/root3/pages/giants/template_stuff/aimages/.. has fi
+lesize of  bytes or 0 k
/home/fred/Desktop/root3/pages/giants/template_stuff/aimages/yjj.jpg h
+as filesize of 237182 bytes or 231.623046875 k
file is /home/fred/Desktop/root3/pages/giants/template_stuff/aimages/y
+jj.jpg
ratio is 2.27081418504902

I'm pretty close on this one now. I know by what amount I want to reduce filesizes to. The syntax I relied on doing it bash style was a percentage. I'm still looking for that option. For what I'm doing right now, I don't want to bias the shapes of the things I post. I handle their shapes with the css. This is what I have now:

sub resize_images  {
use 5.010;
use Path::Class;
use Image::Magick;

my ($rvars) = shift;
my %vars = %$rvars;

$target = 100; 
$bias = 2; 

opendir my $hh, $vars{to_images} or warn "warn  $!\n";
while (defined ($_ = readdir($hh))){
  my $image = Image::Magick->new;
  my $file = file($vars{to_images},$_);
  $image->ReadImage($file);
  $x = $image->Get('filesize');
  my $k = $x/1024;
  say "$file has filesize of $x bytes or $k k";
    if ($k>$target){
      say "file is $file";
      my $ratio = $k/($target+$bias);
      say "ratio is $ratio";
    }  
}

[Aldebaran]

It looks like the only way to use resize is to use the command line. I don't know how to make that happen with perl driving the logic other than through a system command followed by some script you've written. That's what I attempt to do here, but I seem to be hung up on a printf statement. Why is the %s not working in this printf call? I can see on my terminal that the loop is loading all the images in the directory, and that the logic for entering into the inner control seems to work, that is filesizes less than the target value are ignored, which gets rid of . and .. too. What follows is the routine followed by the helper script it creates.

sub resize_images  {
use 5.010;
use Path::Class;
use Image::Magick;

my ($rvars) = shift;
my %vars = %$rvars;

$vars{"target"}= 100;
$vars{"bias"}= 2;
$vars{"helpscript"}= "helper1.sh";
my $file2 = $vars{"helpscript"};
my $path = $vars{"to_images"};
open( my $fh, ">", $file2 )
  or die("Can't open $file2 for writing: $!");
my $cd = "cd $path \n";
print $fh $cd;
my $ls = "ls -lt >>text1.txt\n";
print $fh $ls;

opendir my $hh, $path or warn "warn  $!\n";
while (defined ($_ = readdir($hh))){
  my $image = Image::Magick->new;
  my $file = file($path,$_);
  $image->ReadImage($file);
  $x = $image->Get('filesize');
  my $k = $x/1024;
  say "$file has filesize of $x bytes or $k k";
  if ($k>$vars{"target"}){
    say "file is $file";
    my $ratio = $k/($vars{"target"}-$vars{"bias"});
    say "ratio is $ratio";
    my $percent = 100/$ratio;
    say "percent is $percent";
    my $mogrify_spec = "mogrify -resize %2.2f\% %s\n";  
    printf $fh $mogrify_spec, $percent, $file; 
    #printf $fh "file is $file\n"; 
    }  
  close $fh;
  }
}

$ cat helper1.sh
cd /home/fred/Desktop/root3/pages/raiders/template_stuff/aimages 
ls -lt >>text1.txt
mogrify -resize 40.04%s
$

[Anonymous Monk]

Yes, title should have been How to install ImageMagick module How do I compose an effective node title?