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File Uploader: Images different size after upload
Steve Arnold
29 Posts
Oct 24, 2017 - 8:14 pm

Hey there, 

Just wondering why the file size of images seems to change after they’re uploaded. Please see the following screenshots. Note, file before upload is 177kb, after upload its 117kb.

Before upload:

V6Wm91.jpgImage Enlarger



After upload: 

Image Enlarger



I thought this might have been related to JPEG quality, maybe SP was resizing based on the setting in my File Uploader config:

Image Enlarger



But I’ve tested multiple variations of higher/lower settings in the uploader and higher/lower JPEG quality of the files I’ve uploaded. If this was being caused by this setting, I’d expect images of JPEG quality lower than what’s configured in the above screenshot to NOT be resized, but it appears to be happening in all variations/instances.

Please can you shed any light on this?

Many thanks

Mr Papa
Simi Valley, CA

19448 Posts
Oct 24, 2017 - 9:01 pm

first, none of your images show for me – perhaps not uploaded properly?

multiple things here… first, you may be using different OS’es on your local computer and server… they may (and likely do) compute disk usage differently…  and can be fairly significant dependent on min block size of the  OS…

also, assume you are talking about full size images and not the thumbnails?

you sort of referenced it, but what are your settings on forum – components – file uploads??

Steve Arnold
29 Posts
Oct 24, 2017 - 9:37 pm

That’s weird, I used a site called snaggy to save my screenshots. I’ll save and upload them directly. 

V6Wm91.jpgImage EnlargerYGp5Li.jpgImage EnlargerQBbIM9.jpgImage Enlarger


Thanks for your reply. 

I did read about the operating system difference in another thread but I’m not convinced its that. 

Reason being, I created versions of the same image saved at jpeg quality 100, 90, 80, and 70

On my computer they varied in size with the largest being over 391kb, the smallest 131kb

I then uploaded them with the quality setting in the SP config at 80, then at 100. 

In every case, no matter what image I uploaded or setting was configured, the file size was reduced to between 110kb and 120kb

Yellow Swordfish
Glinton, England

16436 Posts
Oct 25, 2017 - 3:15 am

I am gong to have to call on @Mr Papa to help and advise on the file size question as he has been much more involved in the uploader code than I have. But I am unsure on one point… Are you saying that image quality has been reduced even when set at 100…? Or is this just curiosity about the smaller file size?

Steve Arnold
29 Posts
Oct 25, 2017 - 7:47 pm

It’s the file size reduction I’m querying. It suggests that the file is being processed somehow during upload, rather than just being uploaded. 

I can’t see the JPEG quality info in the exif data so I’m not sure if that’s what’s being changed specifically.

But in checking the EXIF of the uploaded versions of my images I can see that the upload process is also stripping out colour space information and the embedded colour profile. 

Is there any way to turn of any/all processing during upload, so it just uploads the file exactly as-is?

Thanks again

Mr Papa
Simi Valley, CA

19448 Posts
Oct 25, 2017 - 8:34 pm

if the file size is within the limits you provided via options, there is no additional processing…  only if the quality is to be reduced will any processing be applied…  

do you notice any image degradation? normally, even 10 or 20% would be noticeable…

Steve Arnold
29 Posts
Oct 27, 2017 - 12:38 am

The image(s) are within the limits set in the File Uploader settings.

The screenshots attached are from the File Uploader settings page, and from “Jeffreys Exif Viewer” website which I used to analyse the original image and the version I uploaded to my forum then downloaded again.

You’ll see how the file size in this example has been reduced and the colour space information has been stripped.

When it comes to comparing the actual image quality, it’s hard to tell. I can do some further testing but I’m certain that for whatever reason the file is being processed somewhere along the line. 



ex1.jpgImage Enlarger

ex2.jpgImage Enlarger

Mr Papa
Simi Valley, CA

19448 Posts
Oct 28, 2017 - 3:36 pm

afraid I dont really have any ideas…   I have in the past used the uploader and verified the file was untouched size wise…  perhaps the third party library (plupload) we use for uploading has changed how it operates as well..  now that back from business travel hope to try at test this weekend…

for grins, if you upload the image to your server via ftp, what is the file usage of the ftp uploaded file?

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