Quicker image compression

[mariusmandal]

When uploading a 8MB photo, WP used 12 seconds to compress the image to 4 sizes. After a quick mod, it uses 4 seconds to do the same job, without any noticable image quality loss (even though there is a small theoretical one)

Shortly put:
Sort sizes by area from large to small, and always create <this size> from the last image.
(the image size sorting might be done better, without me knowing how to at the moment..)

Why not do it like this? :)

My modifications to wp-admin/includes/image.php, replacing line 122-128 :

foreach($sizes as $size => $info) {
	$newsizes[ $info['width']*$info['height'] ] = $info;
	$sizename[ $info['width']*$info['height'] ] = $size;
}
krsort($newsizes);
foreach($newsizes as $res => $info)
	$sizes[$sizename[$res]] = $info;

$sizes = apply_filters( 'intermediate_image_sizes_advanced', $sizes );

foreach ($sizes as $size => $size_data ) {
	$resized = image_make_intermediate_size( $file, $size_data['width'], $size_data['height'], $size_data['crop'] );
	if ( $resized ) {
		$metadata['sizes'][$size] = $resized;
		$file = str_replace(substr($file, strrpos($file,'.')),
				'-'.$resized['width'].'x'.$resized['height'].substr($file, strrpos($file,'.')),
				$file);
	}
}

[scribu]

I'm not so sure the image quality would always be the same.

But the real deal breaker is that intermediate image sizes aren't always sortable, i.e. you can have a 400x600 size and a 600x400 size. Not to mention cropping.

[mariusmandal]

Replying to scribu:

I'm not so sure the image quality would always be the same.

But the real deal breaker is that intermediate image sizes aren't always sortable, i.e. you can have a 400x600 size and a 600x400 size. Not to mention cropping.

Of course! Bit too quick here.. I was thinking of crop earlier, but forgot it during the process of coding..

BWhat about using the large one, instead of the original one if the resolution is quite different? A 8mpx image is far from a 2mpx in process time.. :)

My multisite users often complain about long image processing time, but maybe this is unique for my site?

[scribu]

Have you tried using ImageMagick instead of GD?

​http://wordpress.org/extend/plugins/imagemagick-engine/

[nacin]

I would think that generating an image off a generated image would result in lower quality. The lossiness would only multiply.

Merging in the IM plugin is definitely something we'd like to do, though.

[scribu]

Yeah, there's already a ticket for that: #6821

If this method works for you, mariusmandal, you should be able to implement it as a plugin.