Gallery Block - Include resized images

[jordan-webdev]

I would expect that the images displayed through the gallery embed would be resized, in order to save bandwidth. I have a gallery with five 600px wide by 350px tall images in a 577px container. I do see that the sizes attribute has been added to them ("max-width: 600px) 100vw, 600px", however, the full 600px image is still the one being loaded, even though some of the images are being resized to only 181px with CSS.

I would expect this to display a smaller version, much like the function wp_get_attachment_image() does. This limits the use of the gallery block, especially on mobile devices where data is a larger consideration.

[youknowriad]

Seems like a duplicate of #13434

[jordan-webdev]

No, I don't mean custom image sizes. I mean, it should automatically scale the image down, even if "full" is selected, just like wp_get_attachment_image() does. The images are 600px by 350px, so I would think that smaller versions of them should exist normally, even without custom sizes, right?

[youknowriad]

I reopened to ensure people than knows more about "Media" can chime in.
In my tests, I do see the srcset with the different image sizes added.

[benoitchantre]

@youknowriad With WordPress 5.2, Gutenberg 6.1 and Twenty Ninteen, I get the following markup:

<li class="blocks-gallery-item">
    <figure>
        <a href="<url to to full size>" class="wp-image-3765">
            <img src="<url to large size>" alt="" data-id="3769">
        </a>
    </figure>
</li>

I see no srcset attribute.

[yduke]

This is definitely a problem when user add like 20 images in 1080p or even 4k size to one gallery block, a thumbnail size for "src" and full size for link will be good.

[moritzebeling]

All images should always get a full srcset, no matter what pixel-size was defined within the editor or what column layout was picked. This is not a bug, it’s missing functionality, making the Gutenberg gallery essentially useless for responsive websites.

[designsimply]

Passing along a report of trouble using the gallery block seen in mobile support:

I am using photo galleries on The Experiential Studios site. If I use Blocks, it loads way slow. If I use Classic editor, the photos shuffle within the editor itself ("random order" unclicked). I need them to stay in the order I put them. Once it shuffle, it takes an hour to put them back in the correct order. Please help!

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The problem with the Classic editor sounds like the issue at Automattic/wp-calypso#14843 h/t @rachelmcr and the problem with the gallery block loading too slowly sounds like this issue.

[skorasaurus]

This is confirmed and can have the needs testing label removed;

It's a duplicate of #9620

(This is ultimately a duplicate of #6177:

Although a theme may properly create multiple images that are smaller;
the gallery block will not use them )

[noisysocks]

Duplicate of #9620 which was in turn moved to Core Trac.

https://core.trac.wordpress.org/ticket/49966