You could calculate the MD5/SHA1 of the image and store this in a separate column in your table, then when you come to check if the image exists you calculate the MD5/SHA1 of the current image and then check that it matches in the database.
Both MD5 and SHA1 are hashing algorithms . MD5 is simple and fast, but it does not provide good security. SHA1 is complex as compared to MD5 and it provides greater level of security.
Here is a well documented article around it StackOverflow .
As for what you’re seeking, no there isn’t any way which implements this Algorithm in the backend and gives you a direct function of:
my_image = ... # a random image that i got from POST
Image.objects.get(image=my_Image)