Jon asked me to file this here. As discussed on the
openclipart.org mailing list, thumbnailing does not
appear to be working correctly.
For instance, if you go here:
The "thumbnail" takes an abnormally long time to load,
for such a small image. The reason is (drumroll
please...) because it's not small. The HTML of the
page causes the _browser_ to scale it down, but the
.png that is sent for the thumbnail is actually 1024x768.
This is extremely noticeable for dialup users.
The correct behavior is probably to only generate a
thumbnail once for each large image, perhaps the first
time any user looks at it, or perhaps when it's
uploaded in the first place, cache said thumbnail for
posterity, then send the cached thumbnail as the
thumbnail each time. In the HTML, the thumbnail
probably should be a _link_ to the full-sized image,
but it should not _be_ the full-sized image.
Ideal size for the thumbnail is arguable, but I would
suggest 128x128 and in PNG format to conform to the
freedesktop.org thumbnail specification. Code for
generating the thumbnail probably needs to be specific
for each format of image, e.g., creating a thumbnail of
a 1280x1024-pixel JPEG is going to be different from
creating a thumbnail of a US-Letter-sized .svg image.
IMO this might be a good reason to prefer doing it at
upload time as opposed to on first view, but whatever.