Announcement

Collapse
No announcement yet.

Wrong Thumbnails display in Explorer

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Wrong Thumbnails display in Explorer

    I've encountered an annoying and potentially serious problem. Similar symptoms have been reported by others but I believe this one may have an entirely different cause. Basically, files I process with Irfanview won't display proper thumbnails in XT File Explorer. I've spent many hours debugging this. I see it with v4.10 but haven't regressed it.

    It seems that Irfanview may be embedding thumbnails (the wrong ones) in the JPG files. The JFIF specification does indeed support this. I have no way of verifying this because I can't find an image viewer that definitely displays a JPGs embedded JFIF thumbnails versus generating them itself or reading XP's Thumbs.db.

    I was planning to use Irfanview tonight to process several thousand JPGs for posting on my site. But now I can't do that since the thumbnails will be wrong.

    Here's what I've learned about the problem:
    * The wrong thumbnails displayed in Explorer are from the original image, not the new (processed) one. This suggests the files contain embedded thumbnails.
    * I've tried deleting Thumbs.db (and emptying recycle bin) and regenerating a new Thumbs.db file - wrong thumbnails are still created in Explorer
    * it doesn't matter how many times I copy the processed files or move them around to new folders, drives, etc.
    * I've tried emailing the file to myself, then saving the attachment on a different drive. The old thumbnail still comes along for the ride.
    * I've tried zipping, then unzipping the file to a new folder. The unzipped files somehow inherit the old thumbnails
    * I've tried renaming files and copying files
    * I've tried deleting the original file (and emptying recycle bin). The new (processed) file still inherits thumbnail from the original. I can even delete the Thumbs.db file and regenerate thumbnails. It still somehow generates the new thumbnail from the original (deleted) file.
    * I tried power cycling my PC to completely flush the file cache from memory
    * I've used File Monitor (Filemon.exe) to monitor exactly what files are accessed during all these operations. The original file is never accessed. For example, I can delete Thumbs.db plus the original file. Then have Explorer automatically regenerate Thumbs.db by exiting and re-entering the folder. A new Thumbs.db file is still generated with wrong thumbnails from the old (original) files. At no point are other Thumbs.db files accessed nor or other .jpgs accessed (including the old files).
    * occurs when I do a resize, compress, color, negative, etc. in Irfanview
    * since many people use these features, they may not realize the thumbs are wrong because they're often similar to the original.
    * does not occur when I do a rotate left or right (thumbnails are OK).
    * Stranger, if I rotate a file which has a wrong thumbnail, the OS properly generates a new, correct thumbnail. However, if I later rotate this file (or even a copy) back to the ORIGINAL orientation, the old thumbnail comes back from the dead! Even if I rename the files or move them to another folder. And even if I delete Thumbs.db or the original file. So perhaps XP generates it's own thumbnail for rotated images but the original (wrong) thumbnail remains in the JFIF header.
    * I can right-click on a new file in Explorer and say Refresh Thumbnail. This indeed generates a new, proper thumbnail. However, Thumbs.db is not updated. When I revisit the folder (or use F5 to refresh) the old (wrong) thumbnail comes back.
    * I've inspected all OS file permissions and attributes for Irfanview generated files. They look OK.
    * I used the DM Thumbs utility to inspect Thumbs.db to verify that it indeed contains wrong thumbnails. Again, I have no way of seeing whether the JPGs actually contain embedded thumbnails. I don't know of any image viewers that claim they definitely read these.
    * Canon Zoombrowser also generates similarly wrong thumbnails for files created in Irfanview. However, the errors are slightly different. For example, if I use Irfanview to crop an image, Explorer generates a proper thumbnail. However, Zoombrowser generates a CROPPED thumbnail from the original file. Again, there has to be some association (cross-linking) with the original file which is carried along with the new files. Even if they're zipped or emailed and re-saved with new filenames in different folders. Deleting Canon's thumbnail files (or XPs) doesn't help. Because when new thumbnail files are regenerated, it still somehow finds the original (old) file (or original thumbnail data) and generates (wrong) thumbnails from this. Again, Filemon indicates that the original file is NEVER accessed during this process.
    * If I take a file created by Irfanview (with a bad thumbnail) and use any other program to save a copy, the new thumbnail is perfectly OK. It's only Irfanview that creates problem files.

    OK, that was probably too much info. But hopefully it allows you to find and nail this bug ASAP. I need to post my files immediately! Keep up the good work!

    - Chris

    #2
    Do you have the options dialog displayed when you save? ("Show options dialog' checkbox at bottom of save dialog) If not, do so. See if "Keep original EXIF data" is checked. If it is, the original thumbnail contained within the image is not changed. If that option is unchecked, the haunted thumbnail should go poof.
    Its: Belongs to "It"
    It's: Shortened form of "It is"
    ---------------------
    Lose: Fail to keep
    Loose: Not tight

    ---------------------
    Plurals do not require apostrophes

    Comment


      #3
      Clever work-around, thanks!

      Hey Matera,

      thanks for the work-around. And just in the nick of time because I was going to post my whole database tonight. It indeed worked, (seems strange). Unfortunately, it blew away my EXIF data, which I require!

      But the good news is I tried unchecking "Keep Original JPG Comment" and that also worked. Fortunately, I can live without comments for now. Hopefully, this can be fixed in a later release since the EXIF spec is of course separate from the JPEG File Interchange Format (JFIF). Not sure why users would want to keep the old thumbnails.

      I found a good explanation:


      thanks again!

      - Chris

      Comment


        #4
        Yeah, I'm glad you found a better way. It would be nice to attack the thumbnails specifically -- in an easy to find way -- without endangering other data.

        I can see how it might be useful to have the original thumbs though. Kind of a quick way to see what the present image was like originally, before it was cropped or otherwise drastically altered. If all viewers had an option to view an embedded thumb or a derived one, life would be easier.
        Its: Belongs to "It"
        It's: Shortened form of "It is"
        ---------------------
        Lose: Fail to keep
        Loose: Not tight

        ---------------------
        Plurals do not require apostrophes

        Comment

        Working...
        X