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Tourvista

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  • "Tourvista" started this thread

Posts: 259

Location: Leicester UK

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1

Thursday, October 13th 2011, 4:15pm

Massive weight difference between two similar panoramas

Hi all,

When I checked my last virtual tour total weight I was very surprised how heavy it was. So I did some tests which delivered a very crazy results.

So here are two panoramas:

(I uploaded the panoramas just in case someone wanted to test it by themselves, but bare in mind that they are very heavy full res panos)

pano1.jpg - 7708 x 3854 - 90 dpi - 14.7 MB - 15,072 KB
pano2.jpg - 7708 x 3854 - 90 dpi - 8.83 MB - 9,048 kB

After run kmakemultires to convert them into tiles (using this configuration ) this are the results:

pano1 - 91 tiles - 818 square px each - 5.28 MB
pano2 - 91 tiles - 818 square px each - 26.5 MB !!!

So how is it possible that a 6 MB lighter can result into a 21 MB heavier tiled-panorama?
I several test having similar results I have to say that I am totally confused!

Cheers!

2

Tuesday, October 18th 2011, 11:04am

Hi,

the initial jpeg compression rate of the source images is already very different,
and also note - the jpeg compression depends on the content!

the pano1.jpg doesn't have details (many single or smooth colored areas) but a very low jpeg compression rate, this make the source image big but smaller after stronger jpeg compression,

pano2.jpg has much more details (gras, trees, ...) and already a higher jpeg compression rate, so the source size is smaller,

try to open them both in the same software and save it with the SAME jpeg compression/quality settings (e.g. 85% in a percent quality system), you should get the same relative filesize difference like when using the tools,

best regards,
Klaus

Tourvista

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  • "Tourvista" started this thread

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Location: Leicester UK

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3

Wednesday, October 19th 2011, 1:49pm

Thank you very much for the reply Klauss,

The jpg compression was the only variable I didn't take into consideration.
I will try to follow your advise and I'll post the new results.

Thank you very much for your hard work!

Cheers!

Zephyr

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Posts: 1,003

Location: Netherlands

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4

Wednesday, October 19th 2011, 7:44pm

If I remember correctly, JPG compression is based by looking at the pixel next to eachother and calculate the difference between it. So lots of the same colors would result in lower filesize.

Tourvista

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  • "Tourvista" started this thread

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Location: Leicester UK

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5

Wednesday, October 26th 2011, 5:39pm

Thanks for the replies.

I've made some tests saving the images with different jpg qualities (10 and 12), formats (baseline standard and optimized) and types (jpg and tiff).

To be honest, I've got similar results with all of them. Same folder weight.

So the weight of all the tiles has nothing to do with how the jpg was saved. It's definitely related to the complexity of the image.

Every tile from the trees panorama, was heavier than the tiles form the room panorama. Hence the massive weight difference .

I guess the mystery is solved.

Cheers

Posts: 1,855

Occupation: Virtual Tours - Photography - Krpano developer

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6

Wednesday, October 26th 2011, 7:34pm

Well no. The lower the jpg level, the more damage/compression. You can get a lower folder weight by starting with an initially high compression level which would overall look really ugly as you're recompressing more and more homogeneous pixels.
Your initial formula was pretty funny, by comparing different input compression levels to the same output levels. I can see how that would be confusing!
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