How Photoshop solved working with files larger than can fit into memory

https://developer.chrome.com/blog/how-photoshop-solved-working-with-files-larger-than-can-fit-into-memory/

by thunderbong • 3 years ago

208 62 3 years ago

developer.chrome.com

It's a bit of a roundabout article, given that it's ostensibly talking about the Web version of Photoshop. Basically, Adobe already solved the problem (for decades, now) with a traditional non-web application by using the filesystem. And the new bit here is that Chrome offers a filesystem for web apps to use [1], so from the web app's point of view, it can still use the same essential solution that the native app would.

It doesn't really go into the guts of how PS actually manages all that data in much detail. Just "it goes to the filesystem in a smart way."

[1] The "origin private file system": https://developer.chrome.com/articles/file-system-access/#ac...

PaulHoule• 3 years ago

... application-based virtual memory has been a thing since CICS on mainframes back in the 1970s.

astrange• 3 years ago

Photoshop can't rely on mmap, because its scratch file implementation is older than most modern OSes, and some systems have virtual memory limits it exceeds, not just physical memory limits. Though I'm not sure the browser even has mmap capability.

kevingadd• 3 years ago

It's unfortunate that there's still no mmap equivalent for I/O in the browser, so you can't do demand paging or anything like that. Nothing approaching zero-copy either, you're typically looking at two copies or more. At least the OS page cache will probably help you out.

NikkiA3• 3 years ago

Scratch files, now that's a memory I'd repressed.

accrual• 3 years ago

Make sure you keep your scratch files on a separate disk for extra performance! 8)

psychphysic• 3 years ago

They used coding and filesystems so the webpages didn't crash.

Cthulhu_• 3 years ago

They created a GUI using Visual Basic to track the killer's IP

jdmoreira• 3 years ago

Photoshop discovered mmap?

wongarsu• 3 years ago

Except when exporting files, where it still has weird size restrictions (somewhere around 10k pixels per side)

cubefox• 3 years ago

That's ironic, given that it's a Chrome blog post. Because recently someone here said that Google / the Chrome team used their market power to kill JPEG XL (a proposed jpeg successor) in favor of AVIF, which has weird size restrictions.

jsheard4• 3 years ago

This is about the web version of Photoshop, there is no mmap there.

mike_hock• 3 years ago

No, we've (collectively) discovered that we have a lot of mature technologies (like mmap), mature platforms and extremely fast hardware, so we created a crippled software development platform on a bloated layout engine so people can get creative again hacking around the arbitrary constraints and design flaws of the platform to solve problems that had been solved 40 years ago.

ElFitz• 3 years ago

Web browser did drastically simplify delivery and deliverability though.

Not that there wouldn’t have been alternatives had web apps not become a thing. It’s just more user-friendly than most current open alternatives (eg apt-get), and more open than most current user-friendly alternatives (eg app stores).

vlovich1233• 3 years ago

Why doesn’t WASM offer a 64-bit mode?

jsheard4• 3 years ago

It's in the works: https://github.com/WebAssembly/memory64

Starting with 32bit had some performance advantages because 64bit runtimes can use virtual memory shenanigans to implement bounds checking with zero overhead. In wasm64 they'll have to do explicit bounds checking instead.

jcparkyn2• 3 years ago

... 64bit runtimes can use...

Did you mean 32bit?

zamadatix• 3 years ago

It's being worked on, it's currently available for development testing in builds of Chrome and Firefox.

RcouF1uZ4gsC• 3 years ago

One the one hand I like 64bits from a technical perspective but, on the other hand, I am not so sure I want to live in a world where a single web app needs to access more than 4 GB of address space.

bonestamp2• 3 years ago

But if the need occurs, you'd rather be forced to download/install an app rather than use a web app? This seems short sighted, especially for occasional tasks that come up where I'd like to just bang it out once with a webapp than install something.

omoikane• 3 years ago

That future is likely inevitable given the increasing size of games and how people would like to run those as web apps.

keville• 3 years ago

Photoshop wasn't the one to solve this, as others have mentioned.

Adobe likely owns the xRes intellectual property, though:

https://en.wikipedia.org/wiki/Macromedia_xRes

resoluteteeth2• 3 years ago

Photoshop wasn't the one to solve this, as others have mentioned.
Adobe likely owns the xRes intellectual property, though:

Photoshop has used scratch files and it's own virtual memory system since long before adobe bought macromedia

jval43• 3 years ago

Now do iOS. Content-aware fill still fails with OOM on iPad Pro, yet works fine on older Macs with less processing power.

MontagFTB• 3 years ago

iOS VM system doesn’t use the disk for paging, so it’s quite a different beast than a machine with TB of available space.

tabtab• 3 years ago

File buffering RAM and/or arrays was invented long before Adobe. The tricky part is probably optimizing the image processing algorithms to fit the filing method(s). For example, if images are split into "tile files", and a given algorithm requires referencing too many files/tiles at a time, creating too much file I/O, then it probably needs to be reworked into a tile-friendly algorithm.

OnlyMortal• 3 years ago

If I recall correctly, TIFF has the ability to tile an image.

evmar2• 3 years ago

I worked on some memory stuff for Figma, a similar app, though it's surely changed since I did.

One interesting thing about Photoshop's perspective is that it's fundamentally about "files", which is like a single bytestream that contains all the picture and which must be transferred to the browser to work on. A Figma document also can refer to images, but in a different way. The sum of the document data (like layout) and the image pixels can be extremely large, like gigabytes, but you can transfer those two things separately from server to client.

chakintosh• 3 years ago

Might be off-topic but always wondered why Figma limits files to 2Gb, even the paid users. I remember once I had to present my work to stakeholders of a large company and when I opened Figma I was met with the dreaded red banner saying I exceeded the 2Gb limit and wouldn't open the file even for viewing. I was frantically posting on the forums and emailing customer support for a solution. Luckily they replied quickly and suggested I create a new file and paste the important bits on it and leave out the old stuff.

evmar2• 3 years ago

It was a memory limit imposed by the browser.

throwawayai2• 3 years ago

Now if only Figma could catch up to Adobe...

aleph_minus_one• 3 years ago

It perhaps will soon:

- https://www.cnbc.com/2022/09/15/adobe-to-acquire-design-plat...

- https://www.theverge.com/2022/9/15/23354532/adobe-figma-acqu...

ChrisMarshallNY• 3 years ago

We were doing that, with the software (scanner drivers and image processing -BIG files) my team wrote, decades ago.

It's very similar to VM. We paged and indexed everything.

mannyv• 3 years ago

I thought this was pretty well-known. Adobe has been running their own VM engine for a long time now. I'm not sure which Photoshop first shipped with it, but given how pretty much everyone in prepress used it it's likely since at least Photoshop 3.

jasomill• 3 years ago

Version 1, actually[1]:

The PS.temp file is a special file created by the Adobe Photoshop program to implement the program's virtual memory scheme. Virtual memory allows you to work on images of nearly any size, by using a hard disk instead of RAM (random-access memory) to hold information. The PS.temp file contains the program's virtual memory information. The file is normally deleted when you quit the program.

For implementation details, see the files UVMemory.p and UVMemory.inc1.p in the source distribution[2].

[1] https://archive.computerhistory.org/resources/access/text/20...

[2] https://computerhistory.org/blog/adobe-photoshop-source-code...

villgax• 3 years ago

Pandas has to deal with the same crap, thankfully Dask & other out of core packages fix the issues

awinter-py• 3 years ago

some sort of spinning metal thing with platters and read heads and magnets and stuff?

myshpa• 3 years ago

A free photoshop alternative, one man show

https://www.photopea.com/

goolz• 3 years ago

Yes! I am a daily user plus the dev seems like a great guy(he did an awesome AMA back in the day). One of the few places I make it a point to whitelist my ad blocker. So glad to see this shout out.

londons_explore• 3 years ago

I think it's a shame the application has to implement this at all.

The application should be giving hints, and then the OS deciding what to load and when.

abujazar• 3 years ago

This is kinda funny. I worked on 400 MB+ files in Photoshop on a Mac with 128 MB memory in 1999.

dhosek• 3 years ago

Donald Knuth used a pre-release version of Photoshop (at Adobe headquarters after the employees had gone home for the day) to process the images for his book 3:16. He was using multiple Macs to parallelize his process, and there were frequent crashes. This was back in the days of Macs with 512K of RAM which makes your 128MB Mac seem positively capacious by comparison.

icehawk• 3 years ago

He stated that would have been in the summer of 1989-- so Macs actually could have had anywhere from 1-128MB.

128MB would be unlikely, but the SE/30 was released in January of the same year.

Dalewyn• 3 years ago

For the newer people clearly unaware, this is known as a "scratch disk"[1][2].

Now git off mah lawn ya greenhorns. :V

[1] https://helpx.adobe.com/photoshop/using/scratch-disks-prefer...

[2] https://en.wikipedia.org/wiki/Scratch_space

fractallyte• 3 years ago

Satori Paint (https://www.satoripaint.com/) achieved the same result (working with too-large files for available RAM) in the late 1990s. Hugely innovative, vector-based painting that looked like bitmap painting! But it was resolution independent (https://www.satoripaint.com/Tutorials/Workingwithverylargeim...).

Here's a gallery (sadly, thumbnails only): https://web.archive.org/web/20070813084252/http://www.animat...

And the original of this page showed how it was possible to zoom into an apparent bitmap image to an incredible degree (demonstrating the vector resolution-independence of Satori): https://web.archive.org/web/20070804225012/http://www.animat... [As far as I recall, it zoomed into the writing on the clipboard on the right, to show a single period!]

Incredible software!

resoluteteeth2• 3 years ago

Satori Paint (https://www.satoripaint.com/) achieved the same result (working with too-large files for available RAM) in the late 1990s.

Desktop photoshop also had the ability to work with files too large for ram in the 90s

hamburglar• 3 years ago

This isn't even Adobe's first attempt at solving this problem. Old, old versions of Photoshop in the early 90's (I believe it was introduced in Photoshop 2.5) had an ancient hack called "quick edit" which would allow you to select a file and then open a "slice" of the file, which is a specified bounding box within the file (and not only x,y coordinates -- it could also select a subset of the color channels). It would then present that chunk of the file as its own standalone document window which you could manipulate to your heart's content, then when you saved it, it wrote the slice back out to the original document. It only supported a subset of graphics formats because each one had to have custom code to read and write the slice data.

ec109685• 3 years ago

I wonder what the intersection of people who do not know what RAM and Virtual Memory are, but interested in this article?

“ The amount of memory also varies from device to device, as you know when you order a new computer or device and specify the amount of Random-Access Memory (RAM) desired. Many of these platforms also support virtual memory, which allows an application to use more memory than is physically available.”

benjifri• 3 years ago

SEO...

How Photoshop solved working with files larger than can fit into memory

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