Instead of enqueueing pixels, you enqueue an offset, and a length of 32 (and the thread will also need the width of the image).
With that data, each thread is able to calculate itself its tasked pixels.
Thus, if I have offset=0 the formula give calculates
(x=0,y=0) to (x=8,y=0).
If I have offset=32 the formula give calculates
(x=8,y=0) to (x=16,y=0).
Those are 8 pixels of 4 bytes each (RGBA).
you can avoid that thread-save problem with imagemagick.
You read an image and $blob=$original->ImageToBlob(); then manipulate all pixels in the blob, and BlobToImage() back.
See this imagemagick post.
And also this Permonk post: Re: reading in raw data into perl's ImageMagick
At least these primitives are ok with threads? (although not your eyes, you see I used seizure inducing red and green lines... sorry for that)
#! perl
use warnings;
use strict;
use threads;
use Image::Magick;
my $image = Image::Magick->new(
size => "600x600",
);
$image->Read("xc:white");
for my $i (200..400){
async{
my $color = $i % 2 ? '#f00' : '#0f0';
$image->Draw(
primitive => 'line',
points => "$i,100 $i,500",
stroke => $color,
);
}->join;
}
$image->Set(magick=>'gif');
my $blob = $image->ImageToBlob();
open(FH,"> $0.gif")or die "$!\n";
print FH $blob;
close FH;
perldoc threads