[Web] Making conditional sizes

Question

Somewhat related to Kai's question on full size downloads, I have a question.
To make a full sized version of the image, I can just call a photo size that is larger than the original file.. e.g.
['photoSizes.hires.width"]=10000,
['photoSizes.hires.height"]=10000,
I know Lightroom will not enlarge the file and so create a full sized version without knowing the actual pixel dimensions.
What I would require is a way of making this photo size only generate if the user chooses to generate it.
Yes, I can hide the file/links to the file conditionally in the code, but the files will still be generated. If the user chooses not to, I'd prefer they didn't have to sit through the generation of such files, not to mention the disk space it would take up (besides which we have no control over output space of the file in Web).
Any ideas?

Answer 1

Here is an example from the TTGClientResponseGallery. It's a workaround, but I too don't know a way to stop rendering of the images completely.
["photoSizes.hires.width"] = function() return nonCSS.enableDownloadImage == true and 10000 or 1 end,
["photoSizes.hires.height"] = function() return nonCSS.enableDownloadImage == true and 10000 or 1 end,
The nonCSS.enableDownloadImage is set with a check box. If it's true, then the image size is at maximum otherwise it's 1 pixel image.
I had this idea last year, when Matthew started with the Hires images in his ClientResponse Gallery.It was a pain to always wait for the re rendering of all images when only one of the image types (thumbnail, large image or hires image) was changed.
Jürgen