Lossless transformations on others than JPEG

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thany2
Posts: 53
Joined: Mon Apr 29, 2013 9:29 am

Lossless transformations on others than JPEG

Post by thany2 »

Some lossless transformations are possible on JPEG. That's good, I like that. But why can't I losslesly rotate a lossless picture? On a losslessly compressed picture, like PNG, any 90-degree rotation, or mirror, is by definition also lossless.

It makes sense that transformations that can be done losslessly on JPEG, can also be done on images that are losslessly compressed. Like PNG, lossless WebP, BMP, GIF, etc.
Using Windows 10 21H1 and loving it. Cheers!
cday
XnThusiast
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Re: Lossless transformations on others than JPEG

Post by cday »

thany2 wrote: Tue Nov 10, 2020 8:59 pm ... why can't I losslessly rotate a lossless picture?
You mean that there isn't a separate 'lossless rotate' action?

On a losslessly compressed picture, like PNG, any 90-degree rotation, or mirror, is by definition also lossless.
It should be, isn't the general sequence:

The source image when opened is converted losslessly to the full pixel matrix;

The rotation is performed losslessly if an appropriate algorithm is used;

The rotated image matrix is saved using a lossless compression method.

So isn't it understood that, provided an appropriate rotation algorithm is used, and the image is resaved using lossless compression, the rotation will be lossless?
thany2
Posts: 53
Joined: Mon Apr 29, 2013 9:29 am

Re: Lossless transformations on others than JPEG

Post by thany2 »

You mean that there isn't a separate 'lossless rotate' action?
No, this *only* works on JPEG, and *no other* image format whatsoever.
So isn't it understood that, provided an appropriate rotation algorithm is used, and the image is resaved using lossless compression, the rotation will be lossless?
Absolutely. A lossless operation on a lossless picture is always lossless.

If you rotate your car, it's still the same car. You don't compress it.

Now as for JPEG lossless operations, can we please have them on lossless file formats too, please?
Using Windows 10 21H1 and loving it. Cheers!
cday
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Location: Cheltenham, U.K.

Re: Lossless transformations on others than JPEG

Post by cday »

thany2 wrote: Fri Nov 13, 2020 3:20 pm Now as for JPEG lossless operations, can we please have them on lossless file formats too, please?
Sorry, which JPEG lossless operations are you referring to, could you please give some examples...
thany2
Posts: 53
Joined: Mon Apr 29, 2013 9:29 am

Re: Lossless transformations on others than JPEG

Post by thany2 »

cday wrote: Fri Nov 13, 2020 3:36 pm
thany2 wrote: Fri Nov 13, 2020 3:20 pm Now as for JPEG lossless operations, can we please have them on lossless file formats too, please?
Sorry, which JPEG lossless operations are you referring to, could you please give some examples...
See my TS ;)
90-degree rotation and mirror.
Using Windows 10 21H1 and loving it. Cheers!
cday
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Posts: 3084
Joined: Sun Apr 29, 2012 9:45 am
Location: Cheltenham, U.K.

Re: Lossless transformations on others than JPEG

Post by cday »

thany2 wrote: Fri Nov 13, 2020 3:20 pm Now as for JPEG lossless operations, can we please have them on lossless file formats too, please?
Isn't a lossless JPEG operation an operation in which the resulting image matrix is saved in a way that avoids introducing additional encoding artifacts?

But that issue doesn't arise with a lossless file format, the conversion is lossless provided a suitable algorithm is used, and saving is lossless...


Wikipedia - JPEG - Lossless editing
thany2
Posts: 53
Joined: Mon Apr 29, 2013 9:29 am

Re: Lossless transformations on others than JPEG

Post by thany2 »

cday wrote: Fri Nov 27, 2020 9:37 am
thany2 wrote: Fri Nov 13, 2020 3:20 pm Now as for JPEG lossless operations, can we please have them on lossless file formats too, please?
Isn't a lossless JPEG operation an operation in which the resulting image matrix is saved in a way that avoids introducing additional encoding artifacts?

But that issue doesn't arise with a lossless file format, the conversion is lossless provided a suitable algorithm is used, and saving is lossless...


Wikipedia - JPEG - Lossless editing
Exactly my reasoning for having these transformations available for lossless formats in addition to JPEG.
Using Windows 10 21H1 and loving it. Cheers!
cday
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Location: Cheltenham, U.K.

Re: Lossless transformations on others than JPEG

Post by cday »

I'm sorry, I don't understand, where exactly can loss be introduced when converting and resaving an image in a lossless format??
mudo_j
Posts: 30
Joined: Fri Feb 17, 2017 7:01 pm

Re: Lossless transformations on others than JPEG

Post by mudo_j »

As I see this, the lossless transformation tool works just fine as it is, doing what it was designed for.
thany2
Posts: 53
Joined: Mon Apr 29, 2013 9:29 am

Re: Lossless transformations on others than JPEG

Post by thany2 »

cday wrote: Fri Nov 27, 2020 10:25 am I'm sorry, I don't understand, where exactly can loss be introduced when converting and resaving an image in a lossless format??
The lossless transformation tool only works for JPEG, I'm asking to enable it also for lossless formats.
mudo_j wrote: Fri Nov 27, 2020 5:49 pm As I see this, the lossless transformation tool works just fine as it is, doing what it was designed for.
Same answer.
Using Windows 10 21H1 and loving it. Cheers!