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You can't download this image

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Re: You can't download this image

#61

Post by plekter »

ghusbands wrote: post #57
paavohtl wrote: post #36

Earlier quoted context omitted.

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.

I don't think they can use jpg directly, that would be a waste of transistors given that the graphics world use other compression formats like etc1, bc, astc and so on.

It is however perfectly possible to decode blocks of JPG on a GPU by using shader code.

Re: You can't download this image

#62

Post by ducktective »

hdjjhhvvhga wrote: post #41
shrx wrote: post #24

Earlier quoted context omitted.

Nevermind, looks like MobaXterm shell provides a non-standard curl implementation: $ which curl curl: aliased to _tob curl After installing curl with apt-get it works.

I hate it when people do that. You can wonder for hours why something obvious doesn't work as it should and in the end discover someone decided to implement something substandard, often for no good reason.

that's every distro and *nix derivation

Re: You can't download this image

#63

Post by Aerroon »

dkersten wrote: post #54
stiray wrote: post #51

Earlier quoted context omitted.

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.

But because they try the rest of us suffer the consequences of more expensive and slower hardware and all kinds of other problems.

Re: You can't download this image

#64

Post by thih9 »

Somehow right clicking + saving worked fine on Safari (desktop). I tried it a couple of times and it worked in all cases; sometimes it took a second, sometimes more. Perhaps the server dropped the connection?

Re: You can't download this image

#65

Post by Aerroon »

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.

I'm pretty sure it only discards the original after x number of other (new) images have been decoded. (Or perhaps it's memory footprint based?)

I ran into a Chrome performance bug years ago with animations, because the animation had more frames than the decoded cache size. Everything ground to a halt on the machine when it happened. Meanwhile older unoptimized browsers ran it just fine.

Re: You can't download this image

#66

Post by masswerk »

can16358p wrote: post #42
masswerk wrote: post #6

Earlier quoted context omitted.

I actually used this to generate graphs in JS/HTML in the 1990s. :-)

Out of curiosity, how was the performance (of course normalized to performance of that era)?

Here's a somewhat older approach splitting charts into linear runs of 1x1 images, which has some statistics at the bottom of each chart:

https://www.masswerk.at/demospace/relayWeb_en/chartset.htm

(Or see https://www.masswerk.at/demospace/relayWeb_en/welcome.htm and select "charts". Total time for calculations and rendering was then in the about 1 sec range. The real problem for using this in production was that these charts could be printed on Windows with Postscript printers only. I think, this was eventually fixed in Windows 98 SE.)

Re: You can't download this image

#67

Post by netizen-936824 »

Tuna-Fish wrote: post #33
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?

Oh no, it's still downloading the one it's displaying on screen. You can even see a spinny thing as the icon of the tab on Chrome. The format allows for showing images when they are partially downloaded, and also allows pushing data that doesn't actually change the image.

Okay? So we still seem to have an accurate representation of the image we want. Why can't I just download that and what's the point of the rest of the data. If we already are seeing the image, the rest of the data is pointless no?

Re: You can't download this image

#69

Post by cesarb »

dkersten wrote: post #54
stiray wrote: post #51

Earlier quoted context omitted.

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.

> I can still point my phone camera at my monitor and capture it that way

Back in the late 1990s/early 2000s (this was so long ago that I cannot quickly find a reference), there were proposals to require all non-professional audio and video recorders to detect a watermark and disable recording when one was found. Needless to say this was a terrible idea, for several reasons.

Re: You can't download this image

#70

Post by chii »

netizen-936824 wrote: post #67
Tuna-Fish wrote: post #33

Earlier quoted context omitted.

Oh no, it's still downloading the one it's displaying on screen. You can even see a spinny thing as the icon of the tab on Chrome. The format allows for showing images when they are partially downloaded, and also allows pushing data that doesn't actually change the image.

Okay? So we still seem to have an accurate representation of the image we want. Why can't I just download that and what's the point of the rest of the data. If we already are seeing the image, the rest of the data is pointless no?

but the browser doesn't know that the image is already done, and since there's still data coming in, the browser is obliged to continue downloading.

you could right click, and copy image, rather than save as. It achieves what you wanted - save a copy of the image.

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