PNG => AVIF => Always bigger files

[vegetable-bits]

Bug Description

I did convert my media library from PNG to AVIF and was shocked the size is always about 30% larger?!
So i thought maybe the png is not really png and only has this file extension. So i checked it with

Steps to reproduce

1. Upload a PNG
2. Check file size

Screenshots

Additional Context

• PHP Version: 8.3
• OS: Linux
• Browser: Chrome
• Plugin Version: 2.6.1
• Device: Desktop

[westonruter]

That's unexpected. The plugin is supposed only use the modern format if it is smaller than the other format: #1836 (comment)

This is the relevant code, I believe:

performance/plugins/webp-uploads/helper.php

Lines 305 to 335 in 9260fcf

	/**
	* Check whether the additional image is larger than the original image.
	*
	* @since 1.0.0
	*
	* @param array{ filesize?: int } $original An array with the metadata of the attachment.
	* @param array{ filesize?: int } $additional An array containing the filename and file size for additional mime.
	* @return bool True if the additional image is larger than the original image, otherwise false.
	*/
	function webp_uploads_should_discard_additional_image_file( array $original, array $additional ): bool {
	$original_image_filesize = isset( $original['filesize'] ) ? (int) $original['filesize'] : 0;
	$additional_image_filesize = isset( $additional['filesize'] ) ? (int) $additional['filesize'] : 0;
	if ( $original_image_filesize > 0 && $additional_image_filesize > 0 ) {
	/**
	* Filter whether WebP images that are larger than the matching JPEG should be discarded.
	*
	* By default the performance lab plugin will use the mime type with the smaller filesize
	* rather than defaulting to `webp`.
	*
	* @since 1.0.0
	*
	* @param bool $preferred_filesize Prioritize file size over mime type. Default true.
	*/
	$webp_discard_larger_images = apply_filters( 'webp_uploads_discard_larger_generated_images', true );
	if ( $webp_discard_larger_images && $additional_image_filesize >= $original_image_filesize ) {
	return true;
	}
	}
	return false;
	}

Usage:

performance/plugins/webp-uploads/hooks.php

Lines 119 to 122 in 9260fcf

	if ( webp_uploads_should_discard_additional_image_file( $metadata, $image ) ) {
	wp_delete_file_from_directory( $destination, $original_directory );
	continue;
	}

Note the code references “WebP” but this is just because it was written from a time before AVIF support was introduced.

[vegetable-bits]

@westonruter I can provide sample images. But I'm unusre about the license and would prefer to sent it in a private communication. So if there is a developer start to work on it, you can ask me.

[the-hercules]

@vegetable-bits
I tried reproducing this but wasn't able to observe the same behavior.

Steps I tested

1. Uploaded the following PNG images:

   • Abstract Whale PNG
   • Apple Circles PNG
   • Berry Bird PNG
   • Coffee Bean PNG

2. After upload, the plugin generated AVIF versions and the corresponding subsizes.

3. In all tested cases, the generated AVIF files were significantly smaller than the original PNG files. Example from my test:

File	Size
abstract-whale-png.png	2.5M
abstract-whale-png.avif	260K
abstract-whale-png-1024x683.avif	40K

The discard logic did not trigger because the AVIF files were smaller than the original PNG.

Next steps

If you're able to share one of the PNG files that reproduces the issue, I can try testing with that as well.

[b1ink0]

@vegetable-bits I would like to test this behavior. If you are okay with it, you can send them privately to me over WordPress Slack: https://wordpress.slack.com/team/U07UQQFVBAN