Disable WP Core Image compression

unoptimize.php

<?php 

// Set JPEG quality to 100 (no compression)
add_filter('jpeg_quality', fn($quality) => 100, 10);

// Prevent compression when using Imagick
add_filter('wp_editor_set_quality', fn($quality, $mime_type) => 100, 10, 2);

// Force PNGs to retain full quality (no compression via Imagick)
add_filter('image_editor_output_format', function($formats) {
    $formats['image/png'] = 'png'; // Ensure PNGs aren't converted to JPEG or compressed
    return $formats;
});

// Optional: prefer Imagick if available (better for quality control than GD)
add_filter('wp_image_editors', function($editors) {
    return ['WP_Image_Editor_Imagick', 'WP_Image_Editor_GD'];
});

// Set default image size to 'full' when inserting into the block editor
add_filter('image_default_size', function() {
    return 'full';
});