Fastly Magento2 Deep Image Optimization "Failed to shrink image" on product lists

TL;DR

For "Failed to shrink image": what was going on With "Enable Deep Image Optimization" on in the Fastly Magento2 extension, product list images rendered at the wrong size / were not resized properly.

Failed to shrink image

Steps

1. What was going on

With "Enable Deep Image Optimization" on in the Fastly Magento2 extension, product list images rendered at the wrong size / were not resized properly. The edge server returned Fastly-Io-Warning: Failed to shrink image on the affected images, which looked like an image-optimization failure.

2. What fixed it

The "Failed to shrink image" warning was a red herring: the actual cause was a missing canvas query argument on the image URLs, so the image optimizer had no target dimensions to shrink to. Adding the canvas argument (e.g. &canvas=262:262) produced correctly sized images, and the reporter confirmed that was the issue. Check that the extension's image URLs include the canvas parameter; with it present the product-list resizing works.

When to use

You are seeing this: The edge server returned Fastly-Io-Warning: Failed to shrink image on the affected images, which looked like an image-optimization failure. Use this skill when you run into "Fastly Magento2 Deep Image Optimization "Failed to shrink image" on product lists".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

In the thread, the question was: With "Enable Deep Image Optimization" on in the Fastly Magento2 extension, product list images rendered at the wrong size / were not resized properly. The edge server returned Fastly-Io-Warning: Failed to shrink image on the affected images, which looked like an image-optimization failure. The verified resolution: The "Failed to shrink image" warning was a red herring: the actual cause was a missing canvas query argument on the image URLs, so the image optimizer had no target dimensions to shrink to. Adding the canvas argument (e.g. &canvas=262:262) produced correctly sized images, and the reporter confirmed that was the issue. Check that the extension's image URLs include the canvas parameter; with it present the product-list resizing works. Thread: https://vectle.com/threads/thrqDBT4WbYacsBWYsWpZfcQ