User talk:BytePilot

well I've done that, but the output is not what we want.

http://hack.rs/cgi-bin/threshold_bitwise.pl

#!/usr/bin/perl -w
use strict;
use CGI;
use CGI::Carp qw(fatalsToBrowser warningsToBrowser);

my $q = CGI->new();

print $q->header;
print $q->start_html;

print $q->p("this is a thing for doing threshholding");
print $q->p("<small>or possibly <i>thresholding</i>?</small>");

print $q->start_form( -enctype => "multipart/form-data" );

print $q->p("file");
print $q->filefield('uploaded_file');
print $q->submit();

print $q->end_form;

# do we have an upload?
my $filehandle = $q->upload('uploaded_file');
if (defined $filehandle) {

    # do shit
    print $q->p("I'm doing shit");

    # no, actually do shit
    my $filename = $q->param('uploaded_file');
    my $tempfile = $q->tmpFileName($filename);

    foreach my $i (0 .. 7) {

        my $n = 2 ** ($i + 8);

        my @ar = ("gm",
                  "convert", "-type", "grayscale", "-colors", 256, "-operator", "ALL AND $n", "-threshold", $n-1,
                  $tempfile,
                  "/var/www/threshold_output/$filename".$i );

        print $q->p("$i : $n : " . join " ", @ar);

        system(@ar) == 0 or carp "system call failed: $?"; #safer than passing a string to system()

        print $q->img({src => "/threshold_output/$filename".$i});
    }
}


print $q->end_html;

I tried doing just the "-operator ALL AND $n" part by itself, it didn't seem to do anything...

--AndyE 14:16, 12 January 2011 (UTC)

Possible sytax error ?

                  "convert", "-type", "grayscale", "-colors", 256, "-operator", "ALL AND $n", "-threshold", $n-1,

Should perhaps be

                  "convert", "-type", "grayscale", "-colors", 256, "-operator", "ALL AND", $n, "-threshold", $n-1,

?

---

yes - seems to need to be "All", "And", "Whatever". Still, here's one that kinds does what we want...

http://hack.rs/cgi-bin/threshold_grayscale.pl

#!/usr/bin/perl -w
use strict;
use CGI;
use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
use List::Util qw(max min);

my $q = CGI->new();

print $q->header;
print $q->start_html;

print $q->p("this is a thing for doing threshholding");
print $q->p("<small>or possibly <i>thresholding</i>?</small>");

print $q->start_form( -enctype => "multipart/form-data" );

print $q->p("file");
print $q->filefield('uploaded_file');
print $q->submit();

print $q->end_form;

# do we have an upload?
my $filehandle = $q->upload('uploaded_file');
if (defined $filehandle) {

    # do shit
    print $q->p("I'm doing shit");

    # no, actually do shit
    my $filename = $q->param('uploaded_file');
    my $tempfile = $q->tmpFileName($filename);

    foreach my $i (0 .. 7) {

        my $n = ((2 ** (8 + $i)) / 2**16 )*100; #as a percentage

        my @ar = ("gm",
                  # "convert", "-type", "grayscale", "-colors", 8, "-threshold", 12.5*$i ."%",
                  "convert", "-type", "grayscale", "-operator",
                    "Gray", "And", $n   ."%",
                    "-threshold", max($n -1, 0) ."%",
                  $tempfile,
                  "/var/www/threshold_output/$filename".$i );

        print $q->p("$i : " . join " ", @ar);

        system(@ar) == 0 or carp "system call failed: $?"; #safer than passing a string to system()

        print $q->img({src => "/threshold_output/$filename".$i});
    }
}


print $q->end_html;

i converted the raw values to percentages of a max because it wasn't working the other way. I'm not clear on the bit depth of the greyscale image. tried setting it with -depth but still no joy. still, this version is kind of working as it is.

--AndyE 15:12, 12 January 2011 (UTC)

it might be better if, rather than laz0ring the same location multiple times, we converted the image to 8 shades of grey and then picked out each shade as a seperate layer with it's own power settings. that's what i was starting to try to do in the commented-out bit above - not sure how to pick out each shade.

probably worth experimenting with both methods on the laser cutter

--AndyE 15:20, 12 January 2011 (UTC)