If I save a jpeg from the internet

If I save a jpeg from the internet,
am I saving a degraded version of what I see, or am I preserving the quality?

is this a joke

Every time you copy a jpeg it gets recompressed, losing 1-5% of its original data. You need to save as .BMP to preserve qality.

no I read jpeg is a lossy format and everytime you save it you are compressing it and losing some quality

this is not a rotational velocidencity meme
I am legit asking

.png works, too.

I'm pretty sure it depend on the site and how they compress their images.
example would be how twitter largely compress any images posted, which why i hate how some artists only upload their art on it.

ok but once it IS on twitter

if I save it, do I get THAT jpeg or my browser/os compresses it further?

Every time someone saves an image, it loses a percentage of what was originally there. Think of it as taking a photograph, and copying it, then taking that copy, and copying it, then taking THAT copy, and copying it.

That's .jpg and .jpeg images. Save .png and .BMP if you want to avoid this.

yes you have already downloaded it onto your browser wtf

wtf is wrong with you all, jpgs get usually compressed when they are uploaded to a site, not when downloaded. So OP if you download a jpg you get the exact same jpg you see online. But if you upload it somewhere else then download again, it will lose quality because it's compressed further when uploaded. Companies do this to save server space.

there are shitty ISP that degrade image quality if you don't use https

Retard.

>But if you upload it somewhere else then download again, it will lose quality because it's compressed further when uploaded.

If I have a jpeg
I upload it to Sup Forums
then I save it
then I upload the saved one
it gets detected as duplicate

this is correct.

If you save a file through your web-browser, there's no additional compression going on. You're getting the file as it is.
However, if you were to open the file in any image editor, save it and choose any quality below maximum, you'll generate artifacts. Continue to repeat that process and you'll end up with an unusable file. Simply up- and downloading stuff does not alter the file.

MP3s however degrade over time relative to the amount they have been played back.

Obvious bait, but I'll bite in case OP is just a retard.

In theory, no. No data is lost from the .jpeg.

Converting a file to .jpeg in the first place (from raw for example) does lose some of the data during compression. None is lost during a copy, however.

Lossy just means the file was compressed and some data removed compared to the original source.

In reality, sites such as facebook, imgur, instagram, hangouts, etc compress the shit out of files uploaded, so a lot of data is lost if you download from facebook compared to getting the jpeg from a friend.

Seeing the difference now isn't the reason to save photos as PNG. PNG uses lossless compression, while JPEG is 'lossy'. What this means is that for each year the JPEG photographs sit on your hard drive, they will lose, on average, roughly 200 bits, assuming you have SATA - it's about 120 bits on IDE, but only 5...10 bits on SCSI, due to rotational velocidensity. You don't want to know how much worse it is on CD-ROM or other optical media.

I started collecting JPEG pictures in about 2001, and if I try to view any of the photos I downloaded back then, even the stuff which was saved at 100% quality and 4:4:4 chroma subsampling, they just look like crap. The shadow detail is terrible, the highlights...well don't get me started. Some of those photos have degraded at a rate of 100 or even 150 bits/year. PNG pictures from the same period still look great, even if they weren't stored correctly, in a cool, dry place. Seriously, stick to PNG, you may not be able to see the difference now, but in a year or two, you'll be glad you did.

stop trying to mislead people so they end up with ruined pictures. i downloaded the photo a few weeks ago, but have been uploading it all over the place, wearing it out. now look at it.

>MP3s however degrade over time relative to the amount they have been played back.
^^^

>rotational velocidensity

I'm so glad you mentioned this, it seems like not enough people know about it.

Worth nothing this doesn't apply to SSDs in the same way, but each time the SSD is accessed in any read/write cycle, some bits are lost. Luckily the degradation time is far longer with an SSD, but even then you should note that the degradation rate is proportional to how many images you are saving. Every 100 images increases the degradation rate by about 6 months. Absolutely unacceptable if you ask me.

...

if this image was audio related retards would believe it and buy a rotational velocidencity prevention cable for $50k.

audiophiles need to be gassed

Because Sup Forums doesn't compress.files you upload. Don't let the jap jew know

Sup Forums doesn't compress them does it

Where can I find a script to screenshot and save a JPEG image multiple times until it's nigger Twitter quality?

#!/bin/bash
feh image.jpg
scrot
killall -9 feh

put this in a x100 loop

you get the idea

unsurprisingly, most of Sup Forums are tech illiterate fucktards who don't know anything

you're saving the file as-is, no additional quality loss, just like any other file

Bitmaps are limited by colors in comparison to a jpeg

It depends on the web server m8
There are plugins on xamp, iis, etc.. that compress jpg

In a normal website i am pretty sure it doesnt.

>inb4 uploading jpg on Sup Forums the hash changes
Sup Forums rips metadata out of the image

This.

That faster the spin, the easier you lose pixels.
That's why jpeg is called a "lossy" image format.

Other picture formats (i.e. bmp, png) have certain mechanisms to keep the pixels tied to their place, but that also makes them bigger files.

The jpeg you download from Sup Forums is different from the one that you uploaded originally though. It's not recompressed, but it did get some information stripped out of it. It's just that Sup Forums compares the one on the servers compared to the one you're uploading, which is why it detects it as a duplicate. It doesn't compare it to the original one that was uploaded, that would mean it would need to save the original as well (or at least information of it) which is stupid.