Re: Image sizing
Posted by
GregChapman on
Nov 24, 2011; 10:23pm
URL: https://support.nabble.com/Image-sizing-tp7027028p7029590.html
Harvey44 wrote
For my own use I have been sizing images to 1000 px and then choosing the 750 pixel size and that seems to work ok.
On the basis of my understanding, I'd say that was good fortune rather than good practice.
Is it BETTER to have a size that is close in size that one that is being "forced" alot (ie I am only forcing from 1000 to 750).
Well, that requires you to drop one pixel in four. I don't think there's any algorithm used that is quite so crude as to do just that. Any algorithm used must involve an element of averaging the value of adjacent pixels to calculate the three to replace the four. And it won't be just a matter of averaging. There'll be different rules if the adjacent pixels are dramatically different in colour as that is likely to represent an edge and you'll want to keep that sharp. I've never read up on this to know exactly how it's done.
Is it ideal just to export sizes the exact size they will be used?
Yes!
I can't see how you doing one, set of averaging only to allow a machine to start with a merely representative selection of pixels that approximates to the original image get it to do it again, can possibly be ideal. I'll accept that in many cases you may not be able to tell the difference - the human brain does a remarkable job in interpreting a jumble of colours on the retina. But it's got to be better to use the best tool for the job, which you retain control of than let another, and adjust it in one step to an image that is the best you can achieve with rather than rely on a machine which is probably optimised to do the conversion fast rather than well.
Is there any difference between using the CSS above, choosing the sizes from the INSERT IMAGE size options or adding width="750" inline? Are those all basically the same in terms of image quality?
Using a CSS resize relies 100% on the visitors browser.
Using the INSERT IMAGE resize relies 100% on the code Nabble uses. (Hopefully it is a better algorithm and it has the benefit that you know the results your visitors are getting. When you rely on visitor's browsers, anything is possible.)
Editing the NAML to force images to display at a given width, is only the CSS approach by another route.
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