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 Post subject: Image Rotation - Things you Might not Know
PostPosted: August 2nd, 2014, 14:57 
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Have you ever came across rotating a JPG image many times and see what might happen after?

Well the Answer here can be explained by looking @ those images which i did already
rotating 50, 100, 200 times - Clockwise and you will be able to know the Diff.


"Science without religion is lame, religion without science is blind." - By Albert Einstein


Everyday we discover something new, means will DIE Learning.

That's why Windows Alerts You guys when you attempt to Rotate Images

:!:


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 Post subject: Re: Image Rotation - Things you Might not Know
PostPosted: August 2nd, 2014, 22:33 
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JPEG is a lossy format, so no surprise really.

Just wondering what the idea behind this research was Einstein9? would there be a reason someone would do it, or is it a technique to achieve some goal?

I take it each rotation you saved? meaning (rotate,save)*200

do it with bitmap and rotated image should still regain integrity


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 Post subject: Re: Image Rotation - Things you Might not Know
PostPosted: August 3rd, 2014, 10:26 
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HaQue wrote:
JPEG is a lossy format, so no surprise really.

Just wondering what the idea behind this research was Einstein9? would there be a reason someone would do it, or is it a technique to achieve some goal?

I take it each rotation you saved? meaning (rotate,save)*200

do it with bitmap and rotated image should still regain integrity


i have to disagree here with you, it depends on the App. you are using
in addition there are some Free/Commercial Apps which makes the same process without destroying the image it self

What is the Point of the post here?

Rotating the Image via Windows normal viewer Will change your image from inside
and its proven here from the examples (images) and this is what the warning of rotation will result

hope this answers ur Q here

:>

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 Post subject: Re: Image Rotation - Things you Might not Know
PostPosted: August 3rd, 2014, 22:16 
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JPEG is not really a format, it is a compression algorithm. So, for a test, open a high quality camera picture in MS paint, do nothing else but click save. You have done NO operations on it at all, but the file size is likely to be at least 60% of original.

So, every single time you save JPEG image, whether you rotate it, edit it, or do nothing, you are running an algorithm on the data that makes up the picture. depending on how the coder implemented the codecs will depend on what the result is. Some programs will not save anything if it detects that you have not done anything to it.

for example if you open a file in Programmers notepad 2, it will not have save enabled until you change something. if you change something, then undo the change, save is disabled again. It is the coders logic that made this possible, not the actual file formats.

Einstein9's warning that JPEG utils can change an image is very valid, and if mage integrity is important to you, then you must be aware of it.

some times when it is important is say you took a high res photo that was 100MB. a pretty darn good image would be there. if you printed it on A4, it would look great. Now if you reduced filesize (and with it, quality) by 50% it would still probably look exactly the same, no visible difference. BUT if your intention was to use the image for a Billboard in a field for example, you probably would notice the difference a LOT.

other places it may be an issue is forensics. Especially if there was any steganography involved


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 Post subject: Re: Image Rotation - Things you Might not Know
PostPosted: August 5th, 2014, 7:30 
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It begs the question, why does the windows viewer modify the file?

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 Post subject: Re: Image Rotation - Things you Might not Know
PostPosted: August 5th, 2014, 12:18 
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Einstein9 doesn't say what he rotated them in or if he saved them between or what the process was
IMHO he would have had to script it somehow so probably not windows viewer maybe photoshop or a Linux cli tool or something
Maybe he will share details

Keatah. Good question. I can only guess the saving routine just stayed as 1. Coders just said save the file after rotation and didn't care to check if it was actually changed apart from rotation or not and just run the jpeg algorithm of whatever the original quality setting was

Think of jpeg storing a picture as an approximation of your picture

To see really bad jpeg. Make a 2 colour bmp black and white with long straight lines and save as jpg

Or save a high red circuit schematic as jpeg :)


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 Post subject: Re: Image Rotation - Things you Might not Know
PostPosted: August 5th, 2014, 14:26 
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Either that or they intended the viewer to be a family photo album, and they figured people would want pics to stay rotated.

I'd rather it modify metadata or create a separate file indicating if a rotation is required.

To me it is sacrilege to modify an original photo or negative. Always work with copies.

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 Post subject: Re: Image Rotation - Things you Might not Know
PostPosted: August 5th, 2014, 23:43 
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I think it is the general view MS seems to have of their customers:

"these people are probably too dumb to even know what jpeg formats are, so lets just put a slider on there for file size to quality and then they should be able to pick a "big good file" or a "small not as good file".

and

"actually they are probably too dumb to know what file formats are anyway, so lets just hide them altogether and we can figure out what they need for them most cases.
and
"the sooner we can get everyone swiping the screen, sharing pictures of their latest apple crumble they bought from the café and other dumb stuff to everyone, with a few taps, the better. Abstract everything away so that the general population don't know how a computer works, or how it does things"

Meanwhile, those of us that need to create networks with a lot of client machines have to try and get around all this sharing and collaboration crap. Libraries, homegroups, "work computer" "home computer" public folders etc... the general population don't even understand those, and we have to try and disable it all.

Even things like the "send to.." "compressed(zipped) file

NO! it is a zip file. call it that. but why make the user worry about what a zip is.. just tell them you have made their data a little smaller and abstract it away, zip is too technical and users are probably too dumb.

If you look at the marketing it as all phrases like "get more done in less time" "easily share with others" "be more productive" really? so to do this they must generalise everything and force people to a few common pathways.

"Office 365 on the devices that you love. Buy now."
really? My experience with Office 365 is dismal. waiting for refreshing, cant select a few hundred emails because the page refreshes the list and you lose the selection, many granular options just gone.. it is nothing like using an installed office product.

"Get all the stuff you love in one place." well the internet did just fine with that until the advertising crap that no one ever buys pretty much made it a useless pile of steaming doggy-doo.

But hey, if you think all the things I love are a weather app, a Netflix and youtube app and "email" that predicts there might be an "action item" or because I typed a hyprlink I would need a preview of the webpage to totally screw up any train of thought... then whatever.

10 points to the people that detect I do not like the way OS's are going these days!!!!


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