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You can't download this image

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Re: You can't download this image

#51

Post by stiray »

causi wrote: post #28

When you usually try to download an image, your browser opens a connection to the server and sends a GET request asking for the image. I'm not a web designer, but that seems rather ass-backwards. I'm already looking at the image, therefore the image is already residing either in my cache or in my RAM. Why it is downloaded a second time instead of just being copied onto my drive?

I have problem understanding what problem is this solving?

When the image is on my screen I can just screenshot it.

This is a common problem, using something in insecure environment, thats why companies are going into such extents to encrypt movies on whole train from source to the display and even those are regularly dumped.

Re: You can't download this image

#52

Post by Karellen »

MildlySerious wrote: post #7
dvh wrote: post #5

If I wanted a non-downloadable image I would make it from 1px wide/tall colored divs.

Pretty sure that was actually used in emails at some point, just with tables, to get around email clients not loading images.

Email clients generally don't load external images. The majority should still display images that are sent as part of a multipart/mixed message though, and those should take up significantly less space than thousands of divs/tds and color attributes.

Re: You can't download this image

#53

Post by Rerarom »

sildur wrote: post #45
kuroguro wrote: post #22

The problem with leaving connections open is that there's a limit on how many you can have on the server... I think the author has committed self-DoS :) https://en.wikipedia.org/wiki/Slowloris_(computer_security)

And now you can't download that image.

Yeah it's like a breeder reactor, it makes its own fuel.

Re: You can't download this image

#54

Post by dkersten »

stiray wrote: post #51
causi wrote: post #28

When you usually try to download an image, your browser opens a connection to the server and sends a GET request asking for the image. I'm not a web designer, but that seems rather ass-backwards. I'm already looking at the image, therefore the image is already residing either in my cache or in my RAM. Why it is downloaded a second time instead of just being copied onto my drive?

I have problem understanding what problem is this solving? When the image is on my screen I can just screenshot it. This is a common problem, using something in insecure environment, thats why companies are going into such extents to encrypt movies on whole train from source to the display and even those are regularly dumped.

And even if they figured out some DRM method to prevent screenshotting/screen recording, I can still point my phone camera at my monitor and capture it that way, if I really want to. There is always a way around whatever they try to do.

If I can see it, I can make a copy of it.

Re: You can't download this image

#55

Post by mkl »

paavohtl wrote: post #36
causi wrote: post #28

When you usually try to download an image, your browser opens a connection to the server and sends a GET request asking for the image. I'm not a web designer, but that seems rather ass-backwards. I'm already looking at the image, therefore the image is already residing either in my cache or in my RAM. Why it is downloaded a second time instead of just being copied onto my drive?

I don't know about browser internals, but I would guess that the browser decodes the image once into a format that can be shown on the page (so from PNG/JPG/WEBP into a RGBA buffer) and then discards the original file. This saves a bit of memory in 99.99% of cases when the image is not immediately saved afterwards.

More likely the original file is saved in the browser cache. That's why it loads faster when you reload the page, and slower when you do a full reload by holding down shift. In Firefox you can see the files with about:cache, and find them in ~/.cache/mozilla/firefox/e1wkkyx3.default/cache2/entries/ or similar (they have weird names with no extension, but the file command will identify them, in their original format). In Chrome they're packed into files with metadata like the URL at the start. You can extract the original file by looking at a file in the cache folder [1] and snipping the header off (you can guess where it is by looking at the file contents with xxd or a hex editor).

More info (and link to a Windows viewer tool) here: https://stackoverflow.com/questions/6133490/how-can-i-read-c...

[1] For me on Linux, Chrome's is ~/.cache/google-chrome/Default/Cache/

Re: You can't download this image

#56

Post by oefrha »

causi wrote: post #28

When you usually try to download an image, your browser opens a connection to the server and sends a GET request asking for the image. I'm not a web designer, but that seems rather ass-backwards. I'm already looking at the image, therefore the image is already residing either in my cache or in my RAM. Why it is downloaded a second time instead of just being copied onto my drive?

You can totally "download" the image in your RAM by right clicking / long pressing -> "copy image" or equivalent in most browsers. It's just not going to be a byte by byte identical file, and may be in a different format, e.g. you get a public.tiff on the clipboard when you copy an image from Chrome or Safari on macOS, even if the source image is an image/svg+xml.

Re: You can't download this image

#57

Post by ghusbands »

paavohtl wrote: post #36
causi wrote: post #28

When you usually try to download an image, your browser opens a connection to the server and sends a GET request asking for the image. I'm not a web designer, but that seems rather ass-backwards. I'm already looking at the image, therefore the image is already residing either in my cache or in my RAM. Why it is downloaded a second time instead of just being copied onto my drive?

I don't know about browser internals, but I would guess that the browser decodes the image once into a format that can be shown on the page (so from PNG/JPG/WEBP into a RGBA buffer) and then discards the original file. This saves a bit of memory in 99.99% of cases when the image is not immediately saved afterwards.

One cool related thing is that (I believe) modern graphics cards (even Intel) can store and use JPG blocks directly from GPU memory, so it's not necessarily beneficial in the long term to convert to RGBA in advance. Though I think no modern browser actually does this, especially given how power-cheap decoding jpeg (with SIMD) already is and how likely it is that gpu bugs would interfere.

Re: You can't download this image

#60

Post by tomxor »

kuroguro wrote: post #22

The problem with leaving connections open is that there's a limit on how many you can have on the server... I think the author has committed self-DoS :) https://en.wikipedia.org/wiki/Slowloris_(computer_security)

> The connection has timed out

Now I really can't download the image

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