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

Sun Jan 15 10:08:44 GMT 2012

You could imagine using php to convert some pictures to gif, but gif tops out at 256 colours.

Maybe the preview image button should scale to the size of the swf if in web mode and then say "if blurred consider...."?

On 15 Jan 2012, at 08:28, Alistair McNaught <Alistair.McNaught at HEAcademy.ac.uk> wrote:

> Quick update
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> Thanks very much all for the further advice and help.
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> I might have confused things a bit by using table image examples – these weren’t the actual images I was trying to get in the LO, I just knew that they would demonstrate the issue best.
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> For my own purposes it’s reasonably simple to swap jpgs for gifs or pngs but I might need to look at adding some guidance for tutors on choosing the best image format and having different free tools to swap from one to the other as required. Whilst the basic gif v jpg guidance is straightforward enough to understand there are often images (like logos with graduated colour swatches) that don’t neatly fall into one category or the other. Maybe ‘if in doubt use png’ is the best rule of thumb.
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> 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 21:04
> To: Xerte discussion list
> Subject: [Xerte] Re: FW: jpgs degrading - is this a new phenomenon?
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> I think you notice it on these pictures as JPEGs don't handle lines very well.
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> Usually the internet rule is when using text, use a GIF as gifs don't pixelate lines like a jpg does.
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> When given big blocks of colour, like on a photo, jpgs are fine
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> On Sat, Jan 14, 2012 at 8:37 PM, Ron Mitchell <ronm at mitchellmedia.co.uk> wrote:
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> Hi Alistair
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> This is all quite predictable and not a server or flash player issue - just a simple fact of viewing raster images at different to actual size. Your LO is set to full screen try switching to default so it's 800 x 600 and you'll see that some pages look better at that size and others look better at full screen?
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> It wouldn't help with all your images but for the example here what about using the Charts > Table page type e.g. http://itq.jisctechdis.ac.uk/xerte/play_85
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> HTH
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> Ron
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> From: xerte-bounces at lists.nottingham.ac.uk [mailto:xerte-bounces at lists.nottingham.ac.uk] On Behalf Of Alistair McNaught
> Sent: 14 January 2012 17:45
> To: Xerte discussion list
> Subject: [Xerte] Re: FW: jpgs degrading - is this a new phenomenon?
> 
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> 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.
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> 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.
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> That’s all the excitement needed for one weekend – I’m signing out now!
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> All the best and thanks for the rapid responses Dave and Pat.
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> 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?
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> 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?)
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> The originals are fine.
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> What's the maximum size? 640 something?
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> On Sat, Jan 14, 2012 at 5:02 PM, Alistair McNaught <Alistair.McNaught at heacademy.ac.uk> wrote:
> 
> Hmmm – here’s the test I did for Pat:
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> 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.
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> <image001.png>
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> Curiouser and curiouser..
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> From: 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
> 
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> Subject: [Xerte] Re: FW: jpgs degrading - is this a new phenomenon?
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> >does it look equally blurry on your PC on that slide? 
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> Yes.
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> Vista/Chrome
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> From: Alistair.McNaught at HEAcademy.ac.uk
> To: 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
> 
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