Resurrecting a jpeg?

If I have the middle part of a jpeg file, can't I display at least some of it? Every fixing tool I've tried says something like "need JPEG header", or "need SOI (start of image?) header".

In article op.0b04w1bqwdg98l@glass, Commander Kinsey
wrote:

If I have the middle part of a jpeg file, can't I display at least some of
it?

usually not.

Every fixing tool I've tried says something like "need JPEG header", or
"need SOI (start of image?) header".

either what you tried is crap or it's not repairable.

On 29 Nov 2019, Commander Kinsey wrote
(in article op.0b04w1bqwdg98l@glass):

If I have the middle part of a jpeg file, can't I display at least some of
it? Every fixing tool I've tried says something like "need JPEG header", or
"need SOI (start of image?) header".

It’s dead, Jim. Usually if the headers are gone, the JPG is toast. In some
cases you can resurrect a dead JPG by using similar headers from another JPG.
This is not reliable, in that it doesn’t always work and if it does you
might get ‘unexpected results’.

This is where having a backup would be a good idea.

On Fri, 29 Nov 2019 19:09:12 -0000, Wolffan wrote:

On 29 Nov 2019, Commander Kinsey wrote
(in article op.0b04w1bqwdg98l@glass):

If I have the middle part of a jpeg file, can't I display at least some of
it? Every fixing tool I've tried says something like "need JPEG header", or
"need SOI (start of image?) header".

It’s dead, Jim. Usually if the headers are gone, the JPG is toast. In some
cases you can resurrect a dead JPG by using similar headers from another JPG.
This is not reliable, in that it doesn’t always work and if it does you
might get ‘unexpected results’.

This is where having a backup would be a good idea.

Why on earth do I have to have the first part? Think back to modem days, viewing a large image in a web browser, it would display it bit by bit as it downloaded. Surely if you only have the second half, you'd just get the top bit of the image missing? Ok, so you don't have the header to tell it what width to use, but surely the user could input that data, or adjust until it looked right?

On Fri, 29 Nov 2019 19:16:00 -0000, Commander Kinsey wrote:

On Fri, 29 Nov 2019 19:09:12 -0000, Wolffan wrote:

On 29 Nov 2019, Commander Kinsey wrote
(in article op.0b04w1bqwdg98l@glass):

If I have the middle part of a jpeg file, can't I display at least some of
it? Every fixing tool I've tried says something like "need JPEG header", or
"need SOI (start of image?) header".

It’s dead, Jim. Usually if the headers are gone, the JPG is toast. In some
cases you can resurrect a dead JPG by using similar headers from another JPG.
This is not reliable, in that it doesn’t always work and if it does you
might get ‘unexpected results’.

This is where having a backup would be a good idea.

Why on earth do I have to have the first part? Think back to modem days, viewing a large image in a web browser, it would display it bit by bit as it downloaded. Surely if you only have the second half, you'd just get the top bit of the image missing? Ok, so you don't have the header to tell it what width to use, but surely the user could input that data, or adjust until it looked right?

Or consider a film. You walk in 5 minutes after the start. You can still enjoy most of it without the first bit!

On 29/11/2019 19:18, Commander Kinsey wrote:
On Fri, 29 Nov 2019 19:16:00 -0000, Commander Kinsey
wrote:

On Fri, 29 Nov 2019 19:09:12 -0000, Wolffan wrote:

On 29 Nov 2019, Commander Kinsey wrote
(in article op.0b04w1bqwdg98l@glass):

If I have the middle part of a jpeg file, can't I display at least
some of
it? Every fixing tool I've tried says something like "need JPEG
header", or
"need SOI (start of image?) header".

It’s dead, Jim. Usually if the headers are gone, the JPG is toast. In
some
cases you can resurrect a dead JPG by using similar headers from
another JPG.
This is not reliable, in that it doesn’t always work and if it does you
might get ‘unexpected results’.

This is where having a backup would be a good idea.

Why on earth do I have to have the first part?Â* Think back to modem
days, viewing a large image in a web browser, it would display it bit
by bit as it downloaded.Â* Surely if you only have the second half,
you'd just get the top bit of the image missing?Â* Ok, so you don't
have the header to tell it what width to use, but surely the user
could input that data, or adjust until it looked right?

Or consider a film.Â* You walk in 5 minutes after the start.Â* You can
still enjoy most of it without the first bit!

Wolffan's REALLY clever. Ask HIM if he can extract that picture from
your source! I'll wager he can't if you cannot do so. ;-)

On Fri, 29 Nov 2019 19:29:17 -0000, David wrote:

On 29/11/2019 19:18, Commander Kinsey wrote:
On Fri, 29 Nov 2019 19:16:00 -0000, Commander Kinsey
wrote:

On Fri, 29 Nov 2019 19:09:12 -0000, Wolffan wrote:

On 29 Nov 2019, Commander Kinsey wrote
(in article op.0b04w1bqwdg98l@glass):

If I have the middle part of a jpeg file, can't I display at least
some of
it? Every fixing tool I've tried says something like "need JPEG
header", or
"need SOI (start of image?) header".

It’s dead, Jim. Usually if the headers are gone, the JPG is toast. In
some
cases you can resurrect a dead JPG by using similar headers from
another JPG.
This is not reliable, in that it doesn’t always work and if it does you
might get ‘unexpected results’.

This is where having a backup would be a good idea.

Why on earth do I have to have the first part? Think back to modem
days, viewing a large image in a web browser, it would display it bit
by bit as it downloaded. Surely if you only have the second half,
you'd just get the top bit of the image missing? Ok, so you don't
have the header to tell it what width to use, but surely the user
could input that data, or adjust until it looked right?

Or consider a film. You walk in 5 minutes after the start. You can
still enjoy most of it without the first bit!

Wolffan's REALLY clever. Ask HIM if he can extract that picture from
your source! I'll wager he can't if you cannot do so. ;-)

Bad wager, I have no experience resurrecting files.

I shall send the incomplete file to him if he wishes to try.

On 29/11/2019 20.16, Commander Kinsey wrote:
On Fri, 29 Nov 2019 19:09:12 -0000, Wolffan wrote:

On 29 Nov 2019, Commander Kinsey wrote
(in article op.0b04w1bqwdg98l@glass):

If I have the middle part of a jpeg file, can't I display at least
some of
it? Every fixing tool I've tried says something like "need JPEG
header", or
"need SOI (start of image?) header".

It’s dead, Jim. Usually if the headers are gone, the JPG is toast. In
some
cases you can resurrect a dead JPG by using similar headers from
another JPG.
This is not reliable, in that it doesn’t always work and if it does you
might get ‘unexpected results’.

This is where having a backup would be a good idea.

Why on earth do I have to have the first part?Â* Think back to modem
days, viewing a large image in a web browser, it would display it bit by
bit as it downloaded.Â* Surely if you only have the second half, you'd
just get the top bit of the image missing?Â* Ok, so you don't have the
header to tell it what width to use, but surely the user could input
that data, or adjust until it looked right?

Consider a ziped file. Alter a byte, the entire thing is lost.

The feature to be able to use a partial file is called "progressive",
and not all formats have it. Sometimes it is an option, and as it makes
the files bigger it is not often used.

--
Cheers, Carlos.

On Fri, 29 Nov 2019 19:45:44 -0000, Carlos E.R. wrote:

On 29/11/2019 20.16, Commander Kinsey wrote:
On Fri, 29 Nov 2019 19:09:12 -0000, Wolffan wrote:

On 29 Nov 2019, Commander Kinsey wrote
(in article op.0b04w1bqwdg98l@glass):

If I have the middle part of a jpeg file, can't I display at least
some of
it? Every fixing tool I've tried says something like "need JPEG
header", or
"need SOI (start of image?) header".

It’s dead, Jim. Usually if the headers are gone, the JPG is toast. In
some
cases you can resurrect a dead JPG by using similar headers from
another JPG.
This is not reliable, in that it doesn’t always work and if it does you
might get ‘unexpected results’.

This is where having a backup would be a good idea.

Why on earth do I have to have the first part? Think back to modem
days, viewing a large image in a web browser, it would display it bit by
bit as it downloaded. Surely if you only have the second half, you'd
just get the top bit of the image missing? Ok, so you don't have the
header to tell it what width to use, but surely the user could input
that data, or adjust until it looked right?

Consider a ziped file. Alter a byte, the entire thing is lost.

The feature to be able to use a partial file is called "progressive",
and not all formats have it. Sometimes it is an option, and as it makes
the files bigger it is not often used.

I'm sure a zip file can be scanned through and the working parts recovered. Eg. a zip file with 10 files of equal sizes inside it. If you corrupt one byte, you only lose one of the files inside. Why would the whole thing depend on one single byte? Consider an mpeg file transmitted over Sky TV etc. An interruption to the signal occurs, you don't lose the whole film.

Commander Kinsey wrote:
Why on earth do I have to have the first part?Â* Think back to modem
days, viewing a large image in a web browser, it would display it bit by
bit as it downloaded.Â* Surely if you only have the second half, you'd
just get the top bit of the image missing?Â* Ok, so you don't have the
header to tell it what width to use, but surely the user could input
that data, or adjust until it looked right?

The big problem is the result of the compression algo. You don't really
have 'part of the picture'. You have a bunch of bits that resulted from
the compression of part of the picture. jpeg/s can be compressed
various ways.

--
Mike Easter