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Comment by kllrnohj | Hacker News Reader

It's not impressive if it's not doing it with ideal sharpness in real-time, which it wasn't.

Tiled zooming into arbitrarily large images is otherwise rather easy to do. Go plop the largest image you can find onto your nearest Android phone and it'll zoom & pan that image at 60fps with nary a stutter or issue. It will take a while for it to re-snap the sharpness as you zoom in, though, but so was the iPad Pro. How fast it was re-decoding at the new scale factor & crop is the interesting question, but one which wasn't covered.

Otherwise we're just talking the same basic tech behind gigapixel viewers. Which isn't interesting or significant in the slightest, and has been used on mobile for years and years and years.

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> It's not impressive if it's not doing it with ideal sharpness in real-time, which it wasn't.

Do you have evidence backing up this claim?

> Go plop the largest image you can find onto your nearest Android phone and it'll zoom & pan that image at 60fps with nary a stutter or issue

I've never seen an Android device composite, pan, and zoom a multi-layer gigapixel image with the same performance I saw today. If you have a video you could share, I'd be interested to see it.

> It will take a while for it to re-snap the sharpness as you zoom in

To let you in a bit, Photoshop was doing the recomposition of the destination region in real-time. And it's not just a single layer that's on display there, but hundreds, composited together while the user zooms in and out on varying regions of the document.

I've once tried using different devices to render a down-scaled version the full-stitch of XKCD Click and Drag. No device I've tried can allow me to zoom and pan at 60fps. On my Mac, there is some noticeable latency when quickly zooming or panning, and it's definitely not 60fps. I have no reason to believe any old Android phone will do it better.

Now I don't doubt that an image viewer specially optimized for zooming and panning huge images like this can do it at 60fps. The typical image viewer likely does not.

You think a many-layered PSD file is comparable to zooming a single image?

That's like wondering why the source + instrumented dev environment uses so much more resources than its compiled, optimized binary.

What a weird confusion to see on HN.

Of course, because it is. It's going to do a tiled render, likely at powers of 2, and all the heavy many-layer PSD stuff is completely asynchronous from the actual panning & zooming.

Or are you so naive you think that anything of significance is happening on or blocking the UI thread such that merely showing "smoothness" in any way reflects anything about the device's performance at actually doing the photoshop work?

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