Thumbnail Managing Standard | ||
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One important thing is to assure that the thumbnail image displays the same information than the original, only in a downscaled version. To make this possible we use the modification time stored in the required 'Thumb::MTime' key and check if it's equal the current modification time of the original. If not we must recreate the thumbnail.
Example 2. Algorithm to check for modification.
if (file.mtime != thumb.MTime) { recreate_thumbnail (); } |
It is not sufficient to do a file.mtime > thumb.MTime check. If the user moves another file over the original, where the mtime changes but is in fact lower than the thumbnail stored mtime, we won't recognize this modification. |
If for some reason the thumbnail doesn't have the 'Thumb::MTime' key (although it's required) it should be recreated in any case.
There are certain circumstances where a program can't or don't want to update a thumbnail (eg. within a history view of your recently edited files). This is legally but it should be indicated to the user that an thumbnail is maybe outdated or not even checked for modifications. |
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Thumbnail Saving | Thumbnail Creation Failures |