Author Topic: Watermarking and double processing jpeg files.  (Read 1398 times)

Offline Jen Mack

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Watermarking and double processing jpeg files.
« on: August 06, 2013, 08:04:45 PM »
Is there a way to get a watermark on a jpeg in a way that doesn't "double process" the file?

When I import my raw+jpegs, sometimes I just want to grab the OOC jpegs and upload them to Amazon S3. If I don't want the watermark, this works fine. But since there has to be some sort of change to the file (I'm assuming it's to bring PM's jpeg engine into play), I'm concerned about double compressing the image.

The file sizes (as reported by windows explorer) seem to tell the story:
OOC jpeg: 6.22 Mb
Watermarked 100% jpeg: 11.5 Mb

I'm guessing the file didn't pick up 5 Mb of detail, during the save. I'd really love to see a way to watermark with out reprocessing the file.

Or is there some setting magic that I'm failing to grasp?

Offline Sven

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Re: Watermarking and double processing jpeg files.
« Reply #1 on: August 06, 2013, 10:25:34 PM »
I'd really love to see a way to watermark with out reprocessing the file.


Hi Jenny!

For a watermark to be applied the file has to be re-processed. How else would have a watermark added to the JPG?

Sven
Changed from behind the cam to one who buys images as I started to run. No cam or lens left.

Offline Kirk Baker

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Re: Watermarking and double processing jpeg files.
« Reply #2 on: August 06, 2013, 11:22:49 PM »
Jenny,

Is there a way to get a watermark on a jpeg in a way that doesn't "double process" the file?

When I import my raw+jpegs, sometimes I just want to grab the OOC jpegs and upload them to Amazon S3. If I don't want the watermark, this works fine. But since there has to be some sort of change to the file (I'm assuming it's to bring PM's jpeg engine into play), I'm concerned about double compressing the image.

The file sizes (as reported by windows explorer) seem to tell the story:
OOC jpeg: 6.22 Mb
Watermarked 100% jpeg: 11.5 Mb

I'm guessing the file didn't pick up 5 Mb of detail, during the save. I'd really love to see a way to watermark with out reprocessing the file.

Sven is right, if a JPEG's image data is changed, it has to be re-compressed.  Only things like IPTC, crop, tag, rating, color class, exif changes, and soft-rotation can be done without altering a JPEG's image data.

As for the size increase, your original JPEG wasn't saved at 100 quality (probably more like 70-75) and when you saved it in PM you probably used a higher quality setting and thus it got larger.

-Kirk

Offline Jen Mack

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Re: Watermarking and double processing jpeg files.
« Reply #3 on: August 08, 2013, 07:27:42 PM »

Sven is right, if a JPEG's image data is changed, it has to be re-compressed.  Only things like IPTC, crop, tag, rating, color class, exif changes, and soft-rotation can be done without altering a JPEG's image data.

As for the size increase, your original JPEG wasn't saved at 100 quality (probably more like 70-75) and when you saved it in PM you probably used a higher quality setting and thus it got larger.

-Kirk
Ok, thanks for taking the time to answer.

Offline Jen Mack

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Re: Watermarking and double processing jpeg files.
« Reply #4 on: August 08, 2013, 08:14:29 PM »
I did some testing and took a Fuji X-E1 OOC jpeg checked the file size, and then developed the raw file in Silkypix at various levels of compression with the following results:
 
OOC: 6,533,080 bytes
SP-95%: 6,388,459 bytes
SP-96%: 7,262,679 bytes
 
So, it looks like that the X-E1 is making jpegs in the 95% quality range.
 
Now to get a jpeg save from Photo Mechanic, re-saving the jpeg to get a watermark (yes, double compression bad) with a file size target of 6.57 MB the quality slider is at 54!
Samples:
 
Original OOC image:
https://s3.amazonaws.com/ShotByJenn/2013-08-06_AZ-Cardinals/20130806_141613_3075.jpg

Silkypix saved at 95% from raw:
https://s3.amazonaws.com/ShotByJenn/2013-08-06_AZ-Cardinals/20130806_141613_3075-95.jpg
 
Photo Mechanic saved at 54% from OOC jpg:
https://s3.amazonaws.com/ShotByJenn/2013-08-06_AZ-Cardinals/20130806_141613_3075-54.jpg

The PM image with sharpening looks the best, to my eye. They're all really close in file size, but trying to understand the compression difference makes me want to go bang my head on a desk for a while.

Offline Kirk Baker

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Re: Watermarking and double processing jpeg files.
« Reply #5 on: August 08, 2013, 10:19:42 PM »
Jenny,

Make sure you also turn on Subsample Chroma, as it contributes significant size savings at any quality level.  If you want near lossless compression turn it off and set the quality to 100.  You'll of course have a larger file size but there should be little to no loss in quality.

Try quality 95 and Subsample Chroma on and compare the results with your other apps.

HTH,

-Kirk