>>If you resize an image, the file contents will change. It may become larger but iac the CRC has to be recalculated - file size changed or not
>>
>>The CRC has to be recalculated anyway - why is it important that the file size is different ?
>
>We have 50 million records representing files on disk with their CRC32 value. On Windows Server 2003, when we resized a JPG image to 640x480, it was resulting in a smaller file in size. On Windows Server 2008, doing the same operation on the same file results in a different file size. So, we cannot identify if this file is in the database or not. We need to avoid duplicates. That worked very well until now. But, we have discovered that the OS has an impact on the file size when it is resized.
>
>For example, Windows 7 and Windows Server 2008 resizes the file to the same file size. But, Windows 8 and Windows Server 2003 resizes the same file to a different file size, which is then different than the other environments. At first, at thought that the .NET Framework DLLs might have been updated resulted in such a change. But, this is not the case. Because, even doing it from LViewPro, on the same file, from different environments, results in the same.


Then I think the actual means ( something + CRC) to identify an image + its size is not the right way to do it

Maybe it would be better to use ( something + its dimensions ), eg file1.jpg + height + width