blurhash.php

<?php

namespace Imgproxy;

if ( file_exists( __DIR__ . '/vendor/autoload.php' ) ) {
	require_once __DIR__ . '/vendor/autoload.php';
}

if ( !class_exists( 'kornrunner\Blurhash\Blurhash' ) ) {
	// Only enable blurhash if we have the vendored dependencies
	return;
}

if ( defined('BLURHASH_DISABLED') && BLURHASH_DISABLED === true ) {
	return;
}

use kornrunner\Blurhash\Blurhash;

defined('BLURHASH_COMPONENTS_X' ) || define('BLURHASH_COMPONENTS_X', 4);
defined('BLURHASH_COMPONENTS_Y' ) || define('BLURHASH_COMPONENTS_Y', 3);
defined('BLURHASH_MAX_RESIZE' ) || define('BLURHASH_MAX_RESIZE', 64);

function calculate_blurhash($attachment_id) {
	$blurhash = blurhash($attachment_id);
	if (!$blurhash) {
		return;
	}

	update_post_meta($attachment_id, '_blurhash', $blurhash);
}
add_action('add_attachment', 'Imgproxy\calculate_blurhash');

function add_background_image_style_to_attachment_images($attr, $attachment, $size) {
	if (defined('REST_REQUEST') && REST_REQUEST) {
		return $attr;
	}

	if (is_admin()) {
		return $attr;
	}

	$blurhash = get_post_meta($attachment->ID, '_blurhash', true);
	// if blurhash is not a string
	if (!$blurhash || !is_string($blurhash)) {
		return $attr;
	}

	list($width, $height) = get_image_dimensions($attachment->ID, $size);
	if (!$width || !$height) {
		return $attr;
	}

	// This is a blurry image anyway, so don't waste too much memory rendering it
	list($width, $height) = wp_constrain_dimensions($width, $height, BLURHASH_MAX_RESIZE, BLURHASH_MAX_RESIZE);

	$style = blurhashToBase64($blurhash, $width, $height);
	if (!$style) {
		return $attr;
	}

	$attr['style'] = sprintf('background-size: cover; background-image: url(%s);', $style);
	return $attr;
}
add_filter('wp_get_attachment_image_attributes', 'Imgproxy\add_background_image_style_to_attachment_images', 10, 3);

function blurhash($attachment_id) {
	$file = get_attached_file($attachment_id);
	if (!$file) {
		return false;
	}

	$image = imagecreatefromstring(file_get_contents($file));
	if (!$image) {
		return false;
	}

	$width = imagesx($image);
	$height = imagesy($image);

	list($width, $height) = wp_constrain_dimensions($width, $height, BLURHASH_MAX_RESIZE, BLURHASH_MAX_RESIZE);
	$image = imagescale($image, $width, $height);

	$pixels = [];
	for ($y = 0; $y < $height; ++$y) {
		$row = [];
		for ($x = 0; $x < $width; ++$x) {
			$index = imagecolorat($image, $x, $y);
			$colors = imagecolorsforindex($image, $index);

			$row[] = [$colors['red'], $colors['green'], $colors['blue']];
		}
		$pixels[] = $row;
	}

	// Adjust components for landscape vs portrait images
	// Wide images should have more components on the x-axis
	// Tall images should have more components on the y-axis
	$components_x = BLURHASH_COMPONENTS_Y;
	$components_y = BLURHASH_COMPONENTS_Y;
	if ($width > $height) {
		$components_x = BLURHASH_COMPONENTS_X;
	} else if ($height > $width) {
		$components_y = BLURHASH_COMPONENTS_X;
	}

	return Blurhash::encode($pixels, $components_x, $components_y);
}

function blurhashToBase64($blurhash, $width, $height) {
	$base64 = wp_cache_get($blurhash . $width . $height, 'blurhash');
	if (!$base64) {
		// Decode the BlurHash to get the color components
		$pixels = Blurhash::decode($blurhash, $width, $height);
		if (!$pixels) {
			return false;
		}

		// Create an image resource
		$image = imagecreatetruecolor($width, $height);
		if (!$image) {
			return false;
		}

		// Fill the image with the decoded pixel colors
		for ($y = 0; $y < $height; $y++) {
			for ($x = 0; $x < $width; $x++) {
				$color = $pixels[$y][$x];
				$r = round($color[0]);
				$g = round($color[1]);
				$b = round($color[2]);
				$colorIndex = imagecolorallocate($image, $r, $g, $b);
				imagesetpixel($image, $x, $y, $colorIndex);
			}
		}

		// Capture the output to a variable
		ob_start();
		imagepng($image);
		$imageData = ob_get_contents();
		ob_end_clean();

		// Destroy the image resource
		imagedestroy($image);

		// Encode the image data to base64
		$base64 = base64_encode($imageData);
		wp_cache_set($blurhash . $width . $height, $base64, 'blurhash');
	}

	return 'data:image/png;base64,' . $base64;
}

if (defined('WP_CLI') && WP_CLI) {
	\WP_CLI::add_command( 'imgproxy generate', function( $args, $assoc_args ) {
		if (empty($args)) {
			\WP_CLI::error('Please provide attachment IDs');
		}

		$args = array_map('intval', $args);
		foreach( $args as $attachment_id ) {
			$blurhash = blurhash($attachment_id);
			update_post_meta($attachment_id, '_blurhash', $blurhash);
		}
	} );
}