Author Topic: Deletes all meta information (-all=)  (Read 3197 times)

surz

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Deletes all meta information (-all=)
« on: April 22, 2015, 01:32:59 AM »
I used C:\exiftool.exe -all= IMG01.jpg to remove all the meta information.
JPG was edited with Adobe Photoshop.
When I open the JPG file with a HEX editor/Notepad++, I can see the 6th-10th bits as 41 64 6F 62 65 (Adobe)
Is it possible to remove this meta information as well?

Phil Harvey

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Re: Deletes all meta information (-all=)
« Reply #1 on: April 22, 2015, 07:35:23 AM »
The JPEG APP14 Adobe segment contains some color information that may severely affect the image appearance if deleted.

From the ExifTool application documentation:

Note that not all groups are deletable, and that the JPEG APP14 "Adobe" group is not removed by default with -All= because it may affect the appearance of the image.

and

5) The "APP" group names ("APP0" through "APP15") are used to delete JPEG application segments which are not associated with another deletable group. For example, specifying -APP14:All= will NOT delete the APP14 "Adobe" segment because this is accomplished with -Adobe:All.

Example:

With Adobe APP14:



Without Adobe APP14:



For this reason, I don't consider the Adobe APP14 to be "metadata".  It contains image data only.  (Although, it is true that the existence of this segment does imply the use of some Adobe product, but then I can probably deduce this information and more by looking at the JPEG quantization tables (via the ExifTool JPEGDigest tag).)

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

surz

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Re: Deletes all meta information (-all=)
« Reply #2 on: April 23, 2015, 01:14:09 AM »
Thanks Phil for your reply!
I usually remove this meta information this way:
The old 6th-10th bits were 41 64 6F 62 65 (Adobe)
and using a HEX editor I replaced them to 00 00 00 00 00 (zeros)
That's it! the meta information is removed 8) (that's all I wanted).
And good news is, it does not reduce the picture quality.
But the bad news is, I have to do it manually for all the files :(
So, instead of deleting those bits, can ExifTool not replace them to 00 (zeros)

StarGeek

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Re: Deletes all meta information (-all=)
« Reply #3 on: April 23, 2015, 02:45:58 AM »
You can delete that tag with
ExifTool -Adobe:All= FILE/DIR

See note 5 under -TAG[+-]=[VALUE] in the docs.
Troubleshooting hints:
* When posting, include your OS, Exiftool version, and type of file you're processing (MP4, JPG, etc).
* Double all percent signs (%) in a Windows batch file.
* If your GPS coords are negative, make sure and set the GpsLatitudeRef and GpsLongitudeRef tags correctly.

Phil Harvey

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Re: Deletes all meta information (-all=)
« Reply #4 on: April 23, 2015, 07:07:32 AM »
I usually remove this meta information this way:
The old 6th-10th bits were 41 64 6F 62 65 (Adobe)
and using a HEX editor I replaced them to 00 00 00 00 00 (zeros)
That's it! the meta information is removed 8) (that's all I wanted).
And good news is, it does not reduce the picture quality.

Sorry to disagree, but it does affect the image.  The "Adobe" is required because it is the APP14 segment identifier.  Try this with the image I posted.

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

kingstyle

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Re: Deletes all meta information (-all=)
« Reply #5 on: January 24, 2016, 05:39:34 PM »
Thanks Phil for your reply!
I usually remove this meta information this way:
The old 6th-10th bits were 41 64 6F 62 65 (Adobe)
and using a HEX editor I replaced them to 00 00 00 00 00 (zeros)
That's it! the meta information is removed 8) (that's all I wanted).
And good news is, it does not reduce the picture quality.
But the bad news is, I have to do it manually for all the files :(
So, instead of deleting those bits, can ExifTool not replace them to 00 (zeros)

Can you tell step by step how do you do this?

Quote
Sorry to disagree, but it does affect the image.  The "Adobe" is required because it is the APP14 segment identifier.  Try this with the image I posted.

How much this affect the image?
« Last Edit: January 24, 2016, 06:33:24 PM by kingstyle »

StarGeek

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Re: Deletes all meta information (-all=)
« Reply #6 on: January 24, 2016, 07:10:06 PM »

Quote
How much this affect the image?

It depends upon the image, most often it won't change anything.  But scroll up to see the post with the two images with the PhotoMe box.  That's an example of an extreme difference.


Can you tell step by step how do you do this?

That's really outside the scope of this forum, you'll want to google info on Hex Editor programs.  But I will tell you that based upon your other post, it won't do what you want.  It actually didn't do anything for the original poster, as all he did was corrupt the name of the adobe block.  All the info was still there for anyone who wanted to look inside the file.
Troubleshooting hints:
* When posting, include your OS, Exiftool version, and type of file you're processing (MP4, JPG, etc).
* Double all percent signs (%) in a Windows batch file.
* If your GPS coords are negative, make sure and set the GpsLatitudeRef and GpsLongitudeRef tags correctly.