watermark-text.php

#!/usr/bin/env php
<?php

require dirname(__DIR__) . '/vendor/autoload.php';
use Jcupitt\Vips;

#Vips\Config::setLogger(new Vips\DebugLogger());

if (count($argv) != 4) {
    echo("usage: ./watermark-text.php input output \"some text\"\n");
    exit(1);
}

$image = Vips\Image::newFromFile($argv[1], [
  'access' => 'sequential',
]);
$page_height = $image->height;

// is this an animated image? open all pages
if ($image->getType("n-pages") != 0) {
    $image = Vips\Image::newFromFile($argv[1], [
      'access' => 'sequential',
      'n' => -1
    ]);

    // the size of each frame
    $page_height = $image->get('page-height');
}

$output_filename = $argv[2];
$text = $argv[3];

$text_mask = Vips\Image::text($text, [
  'width' => $image->width,
  'dpi' => 150
]);

// semi-transparent white text on a blue background
$foreground = [255, 255, 255, 50];
$background = [0, 0, 255, 50];

// and a 10-pixel margin
$margin = 10;

$overlay = $text_mask->ifthenelse($foreground, $background, [
  'blend' => true
]);

// add a margin, with the same background
$overlay = $overlay->embed(
    $margin,
    $margin,
    $overlay->width + 2 * $margin,
    $overlay->height + 2 * $margin,
    [
        'extend' => 'background',
        'background' => $background
    ]
);

// tag as srgb
$overlay = $overlay->copy(['interpretation' => 'srgb']);

// expand to the size of a frame, transparent background, place at the bottom
// left
$overlay = $overlay->embed(
    $margin,
    $page_height - $overlay->height - $margin,
    $image->width,
    $page_height
);

// expand to the full size of the gif roll
$overlay = $overlay->replicate(1, $image->height / $page_height);

// composite on top of the gif
$image = $image->composite2($overlay, 'over');

// and write back
$image->writeToFile($output_filename);