E57 import / export | file size not same size

[Antoine]

Hello,
We have exported a raw FARO laser scanner station from FARO Scene in E57, with the pano image embeeded into the E57 file.

that file is 508Mo

Capture.JPG (12.01 KiB) Viewed 1879 times

that file is being imported into CC , the point cloud is present as well as pano image (broken down into native picture shots + pano image)

Capture2.JPG (188.83 KiB) Viewed 1879 times

then I export again that file again in E57

now that file is 625Mo

Capture3.JPG (10.75 KiB) Viewed 1879 times

Strange isn't it ?
I have imported again that new E57 to see if there was any changed in the file structure from DB view...

Just to let you know that the native E57 file that comes from FARO SCENE returns a warning in CC console

Capture4.JPG (65.44 KiB) Viewed 1879 times

any idea why ?
thanks
antoine

[daniel]

So CC doesn't handle all sensor and camera types (so at least the warning is not unexpected).

And regarding the output E57 size, I guess FARO may use 32bits floats to store some values? (I believe CC only uses 64bits for everything).

I could check that (or find the real culprit) if you are able to send me the file (or maybe a smaller sample that allows to reproduce this).

[Antoine]

Hello Daniel
How can I reach you directly so that I share a download link ?
I am in discussion with Faro to know how the write their e57. More soon.
I guess they comply with e57 specifications.
Antoine

[daniel]

Sorry I only see the message now. I've received the file, thanks.

[daniel]

And I found the cause!

Actually, FARO Scene exports the images in JPG format (i.e. compressed). But CC saves them as PNG (lossless, hence larger). As you have a lot of images in the E57 files, this makes a big difference in terms of size.

I'm a bit reluctant to save in JPG as well, as you can potentially lose some information (especially if you do it multiple times).

[Antoine]

Thank you Daniel
good to know FARO is not storing imagery in lossless format !

[daniel]

For the records, the latest version of CC 2.13.alpha will now save the images as JPG. We realized that the saving time of images as PNG (lossless compression) was huge, which could be a problem with hundreds of images. And this way the E57 file size is much smaller.

Hopefully the loss of quality won't be too harmful...

[Antoine]

hello @daniel
I've just noticed that you intergrated that enhancement in last CC release.
thanks.

by the way I was wondering if CloudCompare could detect checkboard from E57 file ? considering I work with structured scan given in E57 ?
do you provide any feature of tool to make a convolution on B&W pattern such as checkboard ?

we could work in image pano view of the scan instead of pointcloud ?
as E57 stored coordinates in a smart way (polar coordinates) maybe we could find a way ?

an alternative way would be to use openCV toolkit.
https://www.tutorialspoint.com/how-to-f ... ncv-python

Thank you. this is just a follow up to the discussion, I could have created a new ticket for that particular request.
antoine

[daniel]

Hi,

No problem. So we don't provide this capability because we don't use it right now. But I guess we could use it for the 'Align' tool (in addition to spheres) if that's what you mean? Or was it in a more general sense?