image 'stretch' but maintaining aspect ratio

[Michiel Spape]

Hi David et al.,

Just a note - be careful, just because you're stretching from higher to lower resolution doesn't mean it gets to be okay. For instance, let's say you have 2 black pixels, 1 white pixel, 3 blue pixels horizontally, next to one another. You want to decrease size by 50%. There will be 1 black pixel to start with, for sure, but what happens with the rest? Your screen doesn't do half pixels, and although anti-aliasing blurs it in such a way that this isn't too obvious, E-Prime (unless 2.0 changed this) doesn't do that. So, what you get is exactly the same as what you get in MSPaint, by decreasing size of this image. I just tested it, the outcome is 1 black pixel, 0 white pixels, and 2 blue pixels. Why is the 0.5 white pixel rounded down (to 0), but the 1.5 blue pixels are rounded up? (to 2) Beats me. A better coder could give the answer, presumably. Anyway, given a high resolution, these changes may not be immediately noticeable, although - if you're a webcoder - you might've seen the effect of what happens with people who present a huge picture with an img tag saying <img width = "20%">. Ugliness and high server load ensues. As a result, I've always tried telling my students they should process stimulus material as well as possible - and if doing that outside e-prime is more work, then so be it.
Cheers,
Mich

PS: This is me signing off - I'll be back next year, working on a new post doc position over at the Helsinki Institute for Information Technology. 

Dr. Michiel M. Sovijärvi-Spapé
Research Fellow
Perception & Action group
University of Nottingham
School of Psychology
www.cognitology.eu

-----Original Message-----
From: e-prime at googlegroups.com [mailto:e-prime at googlegroups.com] On Behalf Of David McFarlane
Sent: 08 December 2011 15:47
To: e-prime at googlegroups.com
Subject: Re: image 'stretch' but maintaining aspect ratio

John,

About the lack of anti-aliasing during 
stretching...  I have never found this to be a 
problem, but that is because I always start with 
original images at a higher resolution and then 
use "Stretch" to effectively "Shrink" the 
original image, which seems to work OK.

That said, I too think it better to just make the 
orginal images at the size you want displayed, 
and then just let E-Prime display those without 
Stretch.  I like to reserve Stretch just for 
doing crude animations where I have to manipulate 
the image size at run time (although I might also 
use Stretch at times just to be lazy).

-- David McFarlane


At 12/8/2011 09:13 AM Thursday, ben robinson wrote:
>michael's probably got the better suggestion, but i have done this in eprime.
>it requires, as he said, knowing the base size of the pictures.  find
>this info by right clicking on each of your picture's icons in
>windows, selecting properties, and then entering the horizontal and
>vertical pixel information into a List object in eprime.
>unfortunately, i know of no way to do this but by hand.
>next you would set your SlideImage object's y-resolution to be a fixed
>value, say 500 pixels high, and its x-resolution to be [(the original
>y-res) divided by 500 multiplied by (the original x-res)].
>
>ben
>
>On Thu, Dec 8, 2011 at 6:23 AM, Michiel Spape
><Michiel.Spape at nottingham.ac.uk> wrote:
> > Hi,
> > E-Prime is, of course, not quite as 
> convenient as current web-standards, but I see 
> no reason it should be _that_ difficult to 
> arrange. That is, if your images all need to be 
> 500 pixels high, say, and your picture is 
> 200x400, can't you just stretch it by 25% (i.e. 
> width and height become 500/400=125%, or 
> 250x500)? The only thing required is that you 
> need to know the base size of your pictures prior to the stretching operations.
> > Two points, however: E-Prime stretches 
> incredibly badly, it does no form of 
> anti-aliasing whatsoever, so your pictures will 
> become degraded in quality. A lot. Secondly, on 
> that point, and given that it's still 
> science-related, I think it is much better 
> practise to do such things off-line (in 
> photoshop or whatever) - keeping the quality 
> somewhat high and knowing full well in advance 
> what you're going to get. It's a bit of work, but well worth it, generally.
> > Cheers,
> > Mich
> >
> > Dr. Michiel M. Sovijärvi-Spapé
> > Research Fellow
> > Perception & Action group
> > University of Nottingham
> > School of Psychology
> > www.cognitology.eu
> >
> >
> > -----Original Message-----
> > From: e-prime at googlegroups.com 
> [mailto:e-prime at googlegroups.com] On Behalf Of JACanterbury
> > Sent: 08 December 2011 10:47
> > To: E-Prime
> > Subject: image 'stretch' but maintaining aspect ratio
> >
> > Hi all,
> >
> > My research indicates that the answer to my question is 'No' but I
> > thought I'd try a quick post incase someone has found a way to do
> > this.
> >
> > I want to display images without altering the aspect ratio (ie width
> > to height proportions) but to fix one of the dimensions, e.g. height
> > and leave eprime to set the appropriate width so that the image
> > doesn't get stretched/squashed. (easy in css but I haven't seen how it
> > can be done in eprime)
> >
> > Any thoughts?
> >
> > Many thanks,
> >
> > John

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