File size increase x4

In article ,
says…

I wanted to make a pdf using Acrobat6 from a jpg. In PS7 I opened this 949kb jpg file rotated it 180 and saved it as a jpg at 12 quality. The file is now 4824kb.

There were no layers to flatten and no other file manipulation so what caused the x4 increase.

Beemer

Update: I had assumed that saving a jpeg at 12 quality level is saving it at the same resolution as the original but maybe this is where i am wrong?

Note that I am not talking here about savign saving file size by lowering resolution e.g. for the web, I want to retain the original resolution then later convert to pdf

Beemer

Beemer wrote in
news::

In article ,
says…

I wanted to make a pdf using Acrobat6 from a jpg.

For god’s sake, why?

In PS7 I opened
this 949kb jpg file rotated it 180 and saved it as a jpg at 12 quality. The file is now 4824kb.

There were no layers to flatten and no other file manipulation so what caused the x4 increase.

Beemer

Update: I had assumed that saving a jpeg at 12 quality level is saving it at the same resolution as the original but maybe this is where i am wrong?

In more ways than one. Compression level has nothing to do with resolution.

But, no, arbitrarily choosing a compression level and assuming it’s going to be the same a jpg was originally saved at is almost certainly going to be wrong.

And, lastly, you should be able to rotate a jpg losslessly when you want to do it in 90 degree increments, but only with utilities such as the PhotoshopCS browser, ACDSee, or ThumbsPlus.

Note that I am not talking here about savign saving file size by lowering resolution e.g. for the web, I want to retain the original resolution then later convert to pdf

Beemer

In article ,
says…

Beemer wrote in
news::

In article ,
says…

I wanted to make a pdf using Acrobat6 from a jpg.

For god’s sake, why?

In PS7 I opened
this 949kb jpg file rotated it 180 and saved it as a jpg at 12 quality. The file is now 4824kb.

There were no layers to flatten and no other file manipulation so what caused the x4 increase.

Beemer

Update: I had assumed that saving a jpeg at 12 quality level is saving it at the same resolution as the original but maybe this is where i am wrong?

In more ways than one. Compression level has nothing to do with resolution.

But, no, arbitrarily choosing a compression level and assuming it’s going to be the same a jpg was originally saved at is almost certainly going to be wrong.

And, lastly, you should be able to rotate a jpg losslessly when you want to do it in 90 degree increments, but only with utilities such as the PhotoshopCS browser, ACDSee, or ThumbsPlus.

Note that I am not talking here about savign saving file size by lowering resolution e.g. for the web, I want to retain the original resolution then later convert to pdf

Beemer

Your answer included "For god’s sake, why?"

Well so that it and other documents can be made into a pdf file.

Lossless rotation: I did not ask about this as I assumed that a 180 deg rotation in PS although not lossless would not increase the file size by x4.

The problem is I assumed that in opening a jpg as a jpg in Photoshop it would then be fully uncompressed. When I go to save it the jpg saving routine asks me for a "quality level" from 1 to 12. I agree that PS quality levels will be different from whatever saved the original and my understanding is that once compressed and then opened there is no advantage in saving with a higher "quality" compression level than was in the original?

To my point …

Photoshop must know the compression ratio of the original file as it uncompressed it so why does it not allow selection of that same compression which would leave the file size approximately the same instead of 4 timers bigger?

Beemer

Beemer wrote in
news::

In article ,
says…

Beemer wrote in
news::

In article ,
says…

I wanted to make a pdf using Acrobat6 from a jpg.

For god’s sake, why?

In PS7 I opened
this 949kb jpg file rotated it 180 and saved it as a jpg at 12 quality. The file is now 4824kb.

There were no layers to flatten and no other file manipulation so what caused the x4 increase.

Beemer

Update: I had assumed that saving a jpeg at 12 quality level is saving it at the same resolution as the original but maybe this is where i am wrong?

In more ways than one. Compression level has nothing to do with resolution.

But, no, arbitrarily choosing a compression level and assuming it’s going to be the same a jpg was originally saved at is almost certainly going to be wrong.

And, lastly, you should be able to rotate a jpg losslessly when you want to do it in 90 degree increments, but only with utilities such as the PhotoshopCS browser, ACDSee, or ThumbsPlus.

Note that I am not talking here about savign saving file size by lowering resolution e.g. for the web, I want to retain the original resolution then later convert to pdf

Beemer

Your answer included "For god’s sake, why?"

Well so that it and other documents can be made into a pdf file.

A JPEG is an image, not a document.

Resaving a JPEG image *by itself* to pdf cannot gain you anything and will almost certainly lose something.

Lossless rotation: I did not ask about this as I assumed that a 180 deg rotation in PS although not lossless would not increase the file size by x4.

It doesn’t.

Opening an image for editing in Photoshop means it is in memory as an uncompressed image. If you want to save it back into JPEG, it must then recompress the image. Whatever ratio you, the user, selects is what affects the file size on disc.

Lossless 90 degree rotation is a trick which shuffles the order of the bytes in a JPEG file; since the image doesn’t have to be re-compressed, the process is lossless.

The problem is I assumed that in opening a jpg as a jpg in Photoshop it would then be fully uncompressed. When I go to save it the jpg saving routine asks me for a "quality level" from 1 to 12. I agree that PS quality levels will be different from whatever saved the original and my understanding is that once compressed and then opened there is no advantage in saving with a higher "quality" compression level than was in the original?

I have no idea why you would have that understanding. JPEG compression throws away information *every* time it’s re-saved.

To my point …

Photoshop must know the compression ratio of the original file as it uncompressed it so why does it not allow selection of that same compression which would leave the file size approximately the same instead of 4 timers bigger?

You’d have to ask Adobe.

In article ,
says…

A JPEG is an image, not a document.

Resaving a JPEG image *by itself* to pdf cannot gain you anything and will almost certainly lose something.

I did say that I was going to save the jpg AND other items in a pdf fle which as you especially will know is one of the advantages of pdfs.

Opening an image for editing in Photoshop means it is in memory as an uncompressed image. If you want to save it back into JPEG, it must then recompress the image. Whatever ratio you, the user, selects is what affects the file size on disc.

Understood

Lossless 90 degree rotation is a trick which shuffles the order of the bytes in a JPEG file; since the image doesn’t have to be re-compressed, the process is lossless.

Not an issue

The problem is I assumed that in opening a jpg as a jpg in Photoshop it would then be fully uncompressed. When I go to save it the jpg saving routine asks me for a "quality level" from 1 to 12. I agree that PS quality levels will be different from whatever saved the original and my understanding is that once compressed and then opened there is no advantage in saving with a higher "quality" compression level than was in the original?

I have no idea why you would have that understanding. JPEG compression throws away information *every* time it’s re-saved.

I agree with the above answer but I feel it veers away from my understanding/resolution of my perceived problem.

To my point …

Photoshop must know the compression ratio of the original file as it uncompressed it so why does it not allow selection of that same compression which would leave the file size approximately the same instead of 4 timers bigger?

You’d have to ask Adobe.

You are I assume THE Eric Gill?

regards,

Beemer

Beemer wrote in news:MPG.1a834c65d43d7bc9989721
@news-lhr.cableinet.net:

In article ,
says…

A JPEG is an image, not a document.

Resaving a JPEG image *by itself* to pdf cannot gain you anything and will almost certainly lose something.

I did say that I was going to save the jpg AND other items in a pdf fle which as you especially will know is one of the advantages of pdfs.

Your phrasing leaves the impression that you are saving the jpeg as a PDF, then adding other things to it. On review, I’m mistaken. Sorry.

<snip>

Lossless 90 degree rotation is a trick which shuffles the order of the bytes in a JPEG file; since the image doesn’t have to be re-

compressed,

the process is lossless.

Not an issue

Well, yes, it is. Unless you did something else to the file in question, it is directly an issue.

Had you used one of the lossless rotation features, the file size would not have changed, and one more layer of JPEG re-compression would not have been added.

It’s faster, too, especially when you’ve got a number of images to turn, as you can select a group and let it run, no opening and re-saving.

I have no idea why you would have that understanding. JPEG compression throws away information *every* time it’s re-saved.

I agree with the above answer but I feel it veers away from my understanding/resolution of my perceived problem.

The point I’m trying to make is that you have another problem as well.

If you are going to do edits to an image, best to save into a lossless format like Tiff while you are working, place the Tiff in your page layout package, and then make a pdf with the appropriate amount of compression for the target purpose, offset print, office, web, whatever.

Trying to optimize it beforehand means you add another layer of JPEG compression, sacrificing quality, often an extreme amount.

<snippage>

You are I assume THE Eric Gill?

Typographer, sculptor and religious nut?

No. He kicked off in 1940. No relation, other than an admirer of his work and fierce critic of his morals.

In article ,
says…

Beemer wrote in news:MPG.1a834c65d43d7bc9989721
@news-lhr.cableinet.net:

In article ,
says…

A JPEG is an image, not a document.

Resaving a JPEG image *by itself* to pdf cannot gain you anything and will almost certainly lose something.

I did say that I was going to save the jpg AND other items in a pdf fle which as you especially will know is one of the advantages of pdfs.

Your phrasing leaves the impression that you are saving the jpeg as a PDF, then adding other things to it. On review, I’m mistaken. Sorry.
<snip>

Lossless 90 degree rotation is a trick which shuffles the order of the bytes in a JPEG file; since the image doesn’t have to be re-

compressed,

the process is lossless.

Not an issue

Well, yes, it is. Unless you did something else to the file in question, it is directly an issue.

Had you used one of the lossless rotation features, the file size would not have changed, and one more layer of JPEG re-compression would not have been added.

It’s faster, too, especially when you’ve got a number of images to turn, as you can select a group and let it run, no opening and re-saving.

I have no idea why you would have that understanding. JPEG compression throws away information *every* time it’s re-saved.

I agree with the above answer but I feel it veers away from my understanding/resolution of my perceived problem.

The point I’m trying to make is that you have another problem as well.
If you are going to do edits to an image, best to save into a lossless format like Tiff while you are working, place the Tiff in your page layout package, and then make a pdf with the appropriate amount of compression for the target purpose, offset print, office, web, whatever.
Trying to optimize it beforehand means you add another layer of JPEG

Eric,

Many thanks.

Beemer