I don't know why, but after some time my images lose quality.
Yesterday i was checking my old mangas, and many pages were smaller then they used to be. I wanna know why, because this has happend before, i tough it was, when i cleaned my HD with tools to release some space etc (usuall maintainece).

I really wanna know why because it's not only JPG, even PNG are getting smaller and worse quality Please tell me what is Happening if you can...

When you say you check, do you open them with some editor (Example: Paint, Irfan, Xnview) or a normal viewer (Example: Windows Photo Gallery)?

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I don't even, dude, i hope you understand that digital data can't degrade over time (yes, that's why digital data is so awesome). Said that, either someone wrote a nice virus that codes a mass recompression of all your images automatically, or you're doing something wrong. If the program you use for "cleaning" actually applies some recompression, then it would make sense.

User error.

syaoran-kun said:
… digital data can't degrade over time (yes, that's why digital data is so awesome).

Actually data can degrade as with every read/write/copy there is a very slight chance of error, in a process that will eventually cause degradation. Of course this is assuming over a huge amount of time and usage, not what most files see.

That's said, you're completely right and it would not manifest as Jpeg artifacts but as corrupted files.

Tip to OP: check your "cleaning" software. You wouldn't use bleach for your teeth, and the same logic applies here: always read what the product does.

We upgraded your brain whilst you slept.

spoiler

There is only one answer to this strange thing: your pictures were injected by a kind of virus, which downscale the picture inorder to spread itself faster.

I agree with everyone else here, you very likely have a virus. Try running a virus scan, if you have a virus protection program that is, and try to get the virus out. If it's already spread all over your images, they're very likely gone.

Seriously though, run a virus scan!! It'll likely save your computer from just crashing down altogether.

spoilerYou've been exposed to too many high-res/high-quality images and you can't go back. Soon you'll be seeing jpeg_artifacts in real life.

Sounds like you bought a new higher res monitor xD

LOOOL your all funny but i don't have virus, lol like i said i think i have an opition that compreses old files when i'm doing my PC maitainece, like HD cleaning to reallese some space in the HD, i just wanna know if anyone had that problem lol, the images usually become smaller after i do the maintainece there is an option that i think it's ruining my Images COMPRESS OLD FILES TO REALEASE SPACE

AZD-A9S said:
When you say you check, do you open them with some editor (Example: Paint, Irfan, Xnview) or a normal viewer (Example: Windows Photo Gallery)?

I use Normal Viewer but i never rotate nor zoom much because i have a high rez monitor

MirrorMagpie said:
Actually data can degrade as with every read/write/copy there is a very slight chance of error, in a process that will eventually cause degradation. Of course this is assuming over a huge amount of time and usage, not what most files see.

That's said, you're completely right and it would not manifest as Jpeg artifacts but as corrupted files.

Tip to OP: check your "cleaning" software. You wouldn't use bleach for your teeth, and the same logic applies here: always read what the product does.

Yup i think it's that i tryd to check it last time but never did it
i use windows predefenition tools to clean like Defrag and HD clean (don't know if that's the names mine is in Portuguese)

Here is the Name "Disk Cleanup" with the box "Compressed Old Files" i thinks this is the thing that recompresses my images can anyone tell me if i'm right and if i am can you help me, i tought if i putted all my images has READ ONLY that they wouldn't get recompreesed i wanna know if that is correct.

Brufh said:
Here is the Name "Disk Cleanup"

As in Microsoft Disk Cleanup?
No, no this tool does not massively rape your image files.

or to quote wikipedia, since I'm tired and half forgot the compression used -.-

Aside from removing unnecessary files, users also have the option of compressing files that have not been accessed over a set period of time. This option provides a systematic compression scheme. Infrequently accessed files are compressed to free up disk space while leaving the frequently used files uncompressed for faster read/write access times. If after file compression, a user wishes to access a compressed file, the access times may be increased and vary from system to system.

I suppose you could say kind of like zipping or rarring something. I suppose it could corrupt data but it does not unrecoverably rewrite it unless it did so in a corrupted way to begin with but that's not its purpose and not its general behaviour. You'd also not end up with working images anyway. That can only have been done by something that actually resaves your images.

Then i really don't know lol maybe they were small to begin with
-_- i really don't know thank god i have all the mangas backed up in my HD but it only happend to some images like 1 in 100 mostly Double pages they look smaller oh well maybe i'm just crazy gonna check the original source to see if i'm crazy XD

Brufh said:
Yup i think it's that i tryd to check it last time but never did it
i use windows predefenition tools to clean like Defrag and HD clean (don't know if that's the names mine is in Portuguese)

No, that's like saying your car broke down due to entropy increase (the universe's fate as said by the 2rd law of thermodynamics). The process I described would take years, decades, maybe more for data corruption.

tl;dr: You're doing it wrong.

LOL No i'm just crazy lol maybe lol, i just Checked the manga and the source is small to but i really don't know maybe i go used to Hi rez images, i'm getting paranoid -_- ... oh well thanx a lot people sorry for my paranoid mind XD

syaoran-kun said:
*facepalm*

My first reaction.

Chrissues said:
Sounds like you bought a new higher res monitor xD

My first toughts soon afterwards.