Re: [GM-apis] Evaluate/Operator in perl API

[Didster <di...@gm...>]

Hi Bob,

Thanks for your response.  Happy to provide some examples.  Attached are:

160.jpg - The source file

heamar6_logo.png - The watermark I am trying to overlay

160-watermark-im-evaluate.jpg - The results using image magick using
Evaluate to change the opacity prior to overlaying using Compose - perfect.

160-watermark-im-oc.jpg - The results using image magick using Compose
specifying an opacity.  It works, but seems to mess up the transparent
background of the watermark.  I found other posts about this which led me
to Evaluate

160-watermark-gm-no-oc.jpg - The results using Graphics magick with no
opacity during Compose.  This works, although the position is off but thats
probably something else

160-watermark-gm-oc.jpg - The results using Graphics magick with opacity on
Compose.  GM seems to take a 0.0->1.0 float for this value vs IM which
takes a percentage string like "20%" but other than that, no changes.
Image file is lost with a messed up watermark

The code for this is at the bottom of this mail.

I will take a look at CopyOpacity but in the mean time, I'm implementing a
fork using IM.

Cheers
Simon

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;
use lib "../libs";
#use Image::Magick;
use Graphics::Magick;

my $id = 160;
my $mainImgFile = "$id.jpg";
my $mainImgFileAndFolder = File::Spec->catfile( ".", $mainImgFile );
my $wmImgFile = "$id-watermark.jpg";
my $wmImgFileAndFolder = File::Spec->catfile( ".", $wmImgFile );

print "write ", $wmImgFileAndFolder, "\n";
my $mainImageHandle = Graphics::Magick->new();
$x = $mainImageHandle->read( $mainImgFileAndFolder );
die($x) if($x);
my $mWidth = $mainImageHandle->get('width');
my $mHeight = $mainImageHandle->get('height');
my $srcWmOverlay = Graphics::Magick->new();
$x = $srcWmOverlay->read( "heamar6_logo.png" );
die $x if($x);
$srcWmOverlay->Set( Background => 'None' );
$srcWmOverlay->Set( Gravity => 'Center' );
$srcWmOverlay->Resize( geometry => sprintf('%dx%d', int(( $mWidth*0.70 )),
$mHeight ) );
my $srcWmOverlayBg = Graphics::Magick->new( size => sprintf('%dx%d',
$mWidth, $mHeight ) );
$srcWmOverlayBg->Set( Gravity => 'Center' );
$srcWmOverlayBg->Read("xc:transparent");
$srcWmOverlayBg->Composite( compose => 'Over', image => $srcWmOverlay );

#$srcWmOverlayBg->Evaluate(
#  operator => 'Multiply',
#  value    => 0.2,
#  channel  => 'Alpha',
#);

$mainImageHandle->Set( Background => 'None' );
$mainImageHandle->Set( Gravity => 'Center' );
$mainImageHandle->Composite( compose => 'Over', image => $srcWmOverlayBg,
opacity => 0.2 ); # Or 20% for IM
$x = $mainImageHandle->Write( $wmImgFileAndFolder );
die $x if ($x);
undef( $srcWmOverlayBg );
undef( $mainImageHandle );




On Thu, Sep 17, 2015 at 2:51 PM, Bob Friesenhahn <
bfr...@si...> wrote:

> On Wed, 16 Sep 2015, Didster wrote:
>
> Hi,
>> I'm looking to switch to GM from IM for a script that I have that
>> processes around about 60,000 images as IM is
>> god awful slow after the first 1000 or so, even with MP support complied
>> out.  Each source image is resized to a
>> number of destination sizes by:
>>
>> 1. Resize the actual image, if the destination is smaller
>> 2. Center the actual image in a white background the size of the
>> destination
>> 3. Overlay a "watermark" which has been made transparent to different
>> levels using IM
>>
>> For step 2, I was using IM->Extent() which doesnt seem to exist in GM so
>> instead I'm now creating a blank white
>> background and Composing the image over the top, that works fine.
>>
>
> I must apologize for not keeping the PerlMagick API in sync with the
> GraphicsMagick APIs.  The enumeration values have been kept in sync, but I
> have not been adding new commands like 'extent' or 'operator'. Regardless,
> the GraphicsMagick variant of PerlMagick should run well since it is an
> important part of the test suite.
>
> Software which runs slower and slower may be running slower due to memory
> leaks.
>
> Thousands of memory leaks have been fixed in GraphicsMagick since the fork
> from ImageMagick.  ImageMagick was originally utilities which ran and then
> quit so memory leaks were not very important.
>
> On Unix type systems, there is a simple "fix" for memory leak problems in
> a leaky PerlMagick.  The "fix" is to do all image processing in a forked
> process (fork()) which quits after processing a few images.
>
> For step 3, I was using something like this:
>>
>> $wmFileHandle->Evaluate(
>>  operator => 'Multiply',
>>  value    => $opacity,
>>  channel  => 'Alpha',
>> );
>>
>> Where $opacity is an float from 0.0 to 1.0.
>>
>> What would be the equivalent in GM for Perl?  I know using convert its
>> "-operator" e.g.
>>
>> gm convert input.png -operator Opacity Multiply 0.5 output.png
>>
>
> Perhaps using one of the Composite operators would suffice.  It is
> possible to insert an opacity channel using CopyOpacity.  I would need to
> study the math to see if others may be used to manipulate the opacity.
>
> I have also tried leaving the watermark as fully opaque and then using
>>
>> $mainImageHandle->Composite( compose => 'Over', image => $wmFileHandle,
>> opacity => $opacity );
>>
>> But that gives corruption [the same problem I was having with IM, which
>> lead me to switch to Evaluate]
>>
>
> What do you mean by "corruption"?  Are you able to share some sample
> images as well as the desired result?
>
> Don't ignore the 'Montage' operator.  It may be convinced to do exactly
> what you want.
>
> Bob
> --
> Bob Friesenhahn
> bfr...@si..., http://www.simplesystems.org/users/bfriesen/
> GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
>
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