>>Then I think the actual means ( something + CRC) to identify an image + its size is not the right way to do it
>
>That is correct.
>
>>Maybe it would be better to use ( something + its dimensions ), eg file1.jpg + height + width
>
>Yes, but this implies that we control the file name that we receive. We wanted to see if there could be a possibility of working around this. Because, if someone sends us MyHouse.jpg and later on ThisImage.jpg, those will not be the same file name but could be the same image and we would have no way of knowing they are duplicate.

Think you can identity the image you receive with CRC ( I'd rather use MD5 or other method)
If they send the same file with another name, you'll know

Then if you resize it, identify the 'resized' with the original checksum + new height + new width


And on an afterthought - do you need to store the resized image ? Can you resize it just for display purposes when you need it in a certain height and width ?


Don't know which business it is - but could you throw away the previous one if they send you another ?