Legacy ImageMagick Discussions Archive

Hi there,

I have written a Windows Service that utilizes the file system watcher on a folder that gets a ton of images uploaded to it. When it gets notified of a file being put in the directory (or any subdirectory), it spawns a task to check the file to see its current quality setting, creates a new, temporary file based on the original file, sets that file's quality to 70, saves the temp file and finally, writes the temp file over the original file.

I'm having a couple problems with this. First, it looks like IM is crashing in my call to get the information about the original file randomly sometimes (don't have a reproducible case yet, but I'm trying to isolate - it seems to happen fairly frequently) and I can't catch the exception:
Secondly, and far worse, is that at random times, the converted file only contains about 1/3 of the image - the rest is grey. I just went through the logs and found that it seems to only be processing these pictures once (I was thinking it might be processing them multiple times). I also thought maybe it was a concurrency issue (especially since I'm not much versed in parallel programming and it has been a long time since I did much coding at all), but I thought the file system would take care of that. Other files in the same folder process fine. There is a significant size difference in the resulting files with the corrupted files typically around 300 KB, the properly compressed files about 1-3 MB and the original files around 5-6 MB.

In case you were wondering why I didn't use a script (I previously was), it is because I'm monitoring from another server than where the files are and the FileSystemWatcher can throw a lot of events quickly and I didn't want to miss them, so it starts a task to do the work so it can get back to monitoring for changes. I am also using a slightly modified FileSystemWatcher that automatically will reconnect in the event of a loss of connectivity to the source to monitor (https://petermeinl.wordpress.com/2015/0 ... emwatcher/).

I have posted one each of files that are missing data, successfully compressed, and uncompressed, all from the same folder, as well as the code I'm using in my Dropbox. https://www.dropbox.com/sh/4qos9451juhn ... oXgSa?dl=0

If anyone can see what it is that I'm missing and help me out, that would be greatly appreciated. Right now I've got it disabled since yesterday, it corrupted a bunch of files and now I have to go find them and hope there is a backup of them.

Environment:
Image server and compressing server both Windows Server 2012 R2, up to date with patching
ImageMagick 7.0.6(.100) Q8 32-bit
VisualStudio 2017
The "Tamed FileSystemWatcher" from 7/1/15

When do you get notified? Perhaps a file has been created but not yet written to or closed, when you start to read it. Obviously that would cause problems.

IMG_0458.JPG has gray for the bottom two-thirds of rows. Apparently this can happen when IM runs out of resources. The "synchronize" setting might prevent this: see http://www.imagemagick.org/script/comma ... ynchronize . I don't know how to so this in VB.

Your output file should be the same as your input file, but at a lower quality setting. So an obvious check is to compare the two images, and check the RMSE score. A score greater than about 2% would suggest there is an error.

I suspect that you are parsing a file that is not completed yet. I had the same issue inside MagickViewer and I solved it like this: https://github.com/dlemstra/MagickViewe ... ons.cs#L43. I keep trying to access the file until I can exclusively access it. Hope that works for you.