[Xerte] Re: FW: jpgs degrading - is this a new phenomenon?

[Alistair McNaught]

A final version with 3 pairs of images (jpg v png) at  sizes 300, 360 and 550 respectively. In all cases jpgs show significant degradation. PNGs only show degradation at the 550 px point where they are being shrunk from 550 to 470 to fit the space.

In the short term I'll stop using jpegs in favour of pngs and gifs but in the long term I'd be really interested to know why jpegs fare so badly. They will be the format of choice for a lot of less technically inclined users so if it ispossible to determine whether the code has changed and if so to change it back I'd be very grateful.

That's all the excitement needed for one weekend - I'm signing out now!

All the best and thanks for the rapid responses Dave and Pat.

A

From: xerte-bounces at lists.nottingham.ac.uk [mailto:xerte-bounces at lists.nottingham.ac.uk] On Behalf Of Pat Lockley
Sent: 14 January 2012 17:08
To: Xerte discussion list
Subject: [Xerte] Re: FW: jpgs degrading - is this a new phenomenon?

It looks like XOT is stretching them, and so is having to fill in bits (which is degradation via interpolation, which sounds redundant but lacking the words to find a better one - negative amelioration?)

The originals are fine.

What's the maximum size? 640 something?
On Sat, Jan 14, 2012 at 5:02 PM, Alistair McNaught <Alistair.McNaught at heacademy.ac.uk<mailto:Alistair.McNaught at heacademy.ac.uk>> wrote:
Hmmm - here's the test I did for Pat:
First 2 slides of http://itq.jisctechdis.ac.uk/xerte/play_82 show significant quality difference yet the image below shows they are virtually identical in their raw form.

[cid:image001.png at 01CCD2E2.FA720500]

Curiouser and curiouser..




From: xerte-bounces at lists.nottingham.ac.uk<mailto:xerte-bounces at lists.nottingham.ac.uk> [mailto:xerte-bounces at lists.nottingham.ac.uk<mailto:xerte-bounces at lists.nottingham.ac.uk>] On Behalf Of Dave Burnett
Sent: 14 January 2012 16:56
To: Xerte list

Subject: [Xerte] Re: FW: jpgs degrading - is this a new phenomenon?


>does it look equally blurry on your PC on that slide?

Yes.

Vista/Chrome


________________________________
From: Alistair.McNaught at HEAcademy.ac.uk<mailto:Alistair.McNaught at HEAcademy.ac.uk>
To: xerte at lists.nottingham.ac.uk<mailto:xerte at lists.nottingham.ac.uk>
Date: Sat, 14 Jan 2012 16:48:14 +0000
Subject: [Xerte] Re: FW: jpgs degrading - is this a new phenomenon?
Hi Dave / Pat - thanks for quick responses
Yes these shots are all on same laptop - it appears to be a new problem.
The only PCs I have access to are all the same spec but I'd be interested if it looks different on other people's PCs - for example the LO I first spotted it on yesterday is at
http://itq.jisctechdis.ac.uk/xerte/play_79 and page 14 is a slide show navigator. Slide 4 on page 14 is shown below as it renders for me and the original image is also shown superimposed. Notice how the table has become blurry. It wasn't always like that .. does it look equally blurry on your PC on that slide?

[cid:image002.png at 01CCD2E2.FA720500]


Alistair


From: xerte-bounces at lists.nottingham.ac.uk<mailto:xerte-bounces at lists.nottingham.ac.uk> [mailto:xerte-bounces at lists.nottingham.ac.uk<mailto:xerte-bounces at lists.nottingham.ac.uk>] On Behalf Of Dave Burnett
Sent: 14 January 2012 16:36
To: Xerte list
Subject: [Xerte] FW: jpgs degrading - is this a new phenomenon?

Sorry, those are both on the same screen aren't they.

How about Flash version then?
I'm just wondering if they way Flash handles the rendering.
Same effect on a different machine?


From: d_b_burnett at hotmail.com<mailto:d_b_burnett at hotmail.com>
To: xerte at lists.nottingham.ac.uk<mailto:xerte at lists.nottingham.ac.uk>
Subject: RE: [Xerte] jpgs degrading - is this a new phenomenon?
Date: Sat, 14 Jan 2012 11:28:37 -0500
Latest video drivers?


________________________________
From: Alistair.McNaught at HEAcademy.ac.uk<mailto:Alistair.McNaught at HEAcademy.ac.uk>
To: xerte at lists.nottingham.ac.uk<mailto:xerte at lists.nottingham.ac.uk>
Date: Sat, 14 Jan 2012 16:26:22 +0000
Subject: [Xerte] jpgs degrading - is this a new phenomenon?
This seems weird but yesterday I was demonstrating a learning object to some colleagues I was working with and I noticed that the images which I'd carefully crafted to be crisp and sharp and fit the available space were looking pixellated and ugly with lots of jpegy artefacts (like when you save a jpeg at too coarse a setting and get fuzz around lines etc). The originals I uploaded are much higher quality.

[cid:image003.png at 01CCD2E2.FA720500]


However no such degradation is apparent with PNG files as shown below: (as before the original is at the bottom and the Xerte rendered version at the top). In this case the quality is indistinguishable.
[cid:image004.png at 01CCD2E2.FA720500]


Is something taking place in the upload that degrades the jpgs or how is this oddity explained. For the short term I can use PNGs rather than JPGs but it introduces an extra work layer and It doesn't help the dozens of LOs that used to look crisp and now look fuzzy. Any suggestions gratefully received!

A





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