sixel-checkerboard.pl

#!/usr/bin/perl

use constant EOT => chr(4);
use constant BEL => chr(7);
use constant ESC => chr(27);
use constant FONTSCALE => 1.3;

# FIXME this is not idempotent - calling it a second time hoses up the
# terminal
sub get_term_fontsize {
    local $|=1;
    my $oldstty = `stty -g`;
    my $resp;
    my $size;

    system('stty raw -echo min 0');
    print ESC . "]7770;?" . BEL;
    system("stty $oldstty");
    sysread(STDIN, $resp, 9);
    $resp =~ m@;(\d+)@;
    $size = $1;

    return $size;
};

sub print_sample_sixel_image {
    print ESC . "Pq";
    print "#0;2;0;0;0#1;2;100;100;100#2;2;80;80;80\n";
    print "#1??}}GG}}??}}??--\n";
    for (my $j = 0; $j < 2; $j++) {
        my $last = 0;
        for (my $i = 0; $i <= 12; $i++) {
            my $reg = rand(2) + 1;
            print "#" . ($last % 2 ? 1 : 2);
            print chr(63 + (1 << $last));
            $last += 1;
            $last = $last % 6;
        };
        print "-\n";            # end with '-' to break the line
    };
    print ESC . "\\";
};

sub print_sample_sixel_of_height {
    my $height = shift() * FONTSCALE;
    my $width = $height;

    my $grid = [];
    for my $i (1..$height) {
        my $row = [];
        my $val = ($i % 2);
        for (1..$width) {
            push @$row, $val;
            $val = ++$val % 2;
        };
        push @$grid, $row;
    };

    my $sixel_strips = [];
    my $n_strips = 0;
    my $leftover = $height;
    while ($leftover > 6) {
        $n_strips += 1;
        $leftover -= 6;
    };
    if ($leftover > 0) {
        $n_strips += 1;
    };

    for my $stripnum (0..$n_strips-1) {
        my $sixel_strip = [];
        my $minrow = $stripnum * 6;
        my $maxrow = $minrow + 5;
        if ($maxrow > ($height-1)) {
            $maxrow = $height - 1;
        };

        for my $col (0..$width-1) {
            my $sixel_val = 0;
            my $shl = 0;
            for my $row ($minrow..$maxrow) {
                my $pixel = $grid->[$row]->[$col];
                if ($pixel == 1) {
                    $sixel_val += (1 << $shl);
                };
                $shl += 1;
            };
            push @$sixel_strip, $sixel_val;
        };

        push @$sixel_strips, $sixel_strip;
    };

    print ESC . "Pq";
    print "#1;2;100;100;100\n";
    # foreach my $sixel_row (@$sixel_strips) {
    for (my $i = 0; $i < scalar(@$sixel_strips); $i++) {
        my $sixel_row = $sixel_strips->[$i];
        print "#1";
        foreach my $sixel_col (@$sixel_row) {
            print chr(63+$sixel_col);
        };
        print '-' if ($i < (scalar(@$sixel_strips))-1);
        print "\n";
    };
    print ESC . "\\";
};

# print_sample_sixel_image();

$term_fontsize = get_term_fontsize();
print_sample_sixel_of_height($term_fontsize);
print "lol!";
print_sample_sixel_of_height($term_fontsize);
print "\n";