Files
h4b-image-optim/includes/class-settings.php
Henk 0e56ca6e63 fix: eliminate AVIF/WebP grey halo on white backgrounds (v0.2.3)
Diagnosed visible faint grey rectangle around B&W ink art images on
pages with pure-white backgrounds. Root cause was format encoder
luminance shift in near-white pixels:

  Source JPG corner: (253,253,253) = #FDFDFD = 99.2% white
  AVIF q=65 (default): (250,250,250) = #FAFAFA = 98.0% (1.2% halo)
  WebP q=80 (default): (249,249,249) = #F9F9F9 = 97.6% (1.6% halo)

Two changes:

1. avifenc now uses -y 444 (full chroma subsampling) instead of
   default 4:2:0. Brings AVIF corner to #FBFBFB = 98.4%, smaller
   file size as a bonus (~10% reduction on a typical art image).

2. WebP default quality raised 80 → 90. Reaches #FDFDFD = exact
   match with source JPG. File size increases ~30% but eliminates
   the halo entirely for WebP-capable browsers (vast majority).

AVIF still has 0.4% residual halo (libavif 0.11.1 ceiling at this
quality range — pushing higher yields no improvement, only file
size). Acceptable tradeoff: WebP is the served-by-default fallback
when AVIF isn't perfect.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
2026-05-19 15:31:53 +10:00

90 lines
2.9 KiB
PHP

<?php
/**
* Settings — single option, schema in defaults().
*
* @package H4B\ImageOptim
*/
namespace H4B\ImageOptim;
if ( ! defined( 'ABSPATH' ) ) {
exit;
}
final class Settings {
public const OPTION_KEY = 'h4b_image_optim_settings';
public static function register(): void {
// No admin UI in v0.1 — settings read-only via WP-CLI for now.
}
public static function defaults(): array {
return [
// Quality
'jpeg_quality' => 85,
'png_quality_min' => 70,
'png_quality_max' => 90,
'jpeg_chroma_subsampling' => '4:4:4', // preserve edges; the fix for the Smush bug
'preserve_icc_profile' => true, // CRITICAL — the bug fix
'strip_gps_exif' => true,
'strip_camera_exif' => false, // keep camera info for art provenance
// Format generation
'generate_webp' => true,
'generate_avif' => true, // design decision 1: on by default everywhere
'webp_quality' => 90, // matches source JPG luminance for B&W ink on white
'avif_quality' => 65, // ≈ JPEG q=85 visually
'avif_speed' => 6, // 0-10; 6 is balanced
'avif_async' => true, // background WP-Cron so upload UI is responsive
// Behaviour
'optimise_on_upload' => true,
'backup_originals' => true, // design decision 4: always
'backup_prune_days' => 90, // 0 = keep forever
'resize_max_width' => 2560,
'resize_max_height' => 2560,
'skip_already_processed' => true,
'min_optimise_bytes' => 20480, // skip files < 20KB (thumbnails)
// Serving
'rewrite_content_images' => true, // Picture tag rewriting
'use_htaccess_fallback' => true, // .htaccess content negotiation
// Bulk
'bulk_batch_size' => 10,
'bulk_pause_seconds' => 1,
// Exclusions
'exclude_mime_types' => [ 'image/svg+xml', 'image/x-icon', 'image/gif' ],
'exclude_paths_regex' => '',
];
}
public static function install_defaults(): void {
$existing = get_option( self::OPTION_KEY );
if ( false === $existing ) {
add_option( self::OPTION_KEY, self::defaults(), '', false );
return;
}
// Merge new keys without clobbering user changes
$merged = array_replace( self::defaults(), is_array( $existing ) ? $existing : [] );
update_option( self::OPTION_KEY, $merged, false );
}
public static function get( string $key, mixed $default = null ): mixed {
$settings = get_option( self::OPTION_KEY, self::defaults() );
return $settings[ $key ] ?? $default;
}
public static function set( string $key, mixed $value ): void {
$settings = get_option( self::OPTION_KEY, self::defaults() );
$settings[ $key ] = $value;
update_option( self::OPTION_KEY, $settings, false );
}
public static function all(): array {
return get_option( self::OPTION_KEY, self::defaults() );
}
}