Hi David, > > Since I haven't been able to find a function within the libraries that I > > could use as a starting point (and of course I do not want to re-invent > > the wheel), my question is, if there is such a function that would > > provide an identical value for any identical image - or would I have to > > write a kind of pre-filter in order to generate that value ? > > What you are talking about is a hash function. There is a string > hasher in GLib that should do what you want. Quite so, yes - thank you, I'll try that out. > However, be aware, > the criteria 'a random number seed that is unique for every image that > is going to be processed,' cannot be fulfilled in an absolute way. > With a hash value of 32bits, that's > 4 billion possible hashes. > Practically speaking, you are likely to encounter a hash collision* > unless the amount of images in the set you're processing gets very > large, you should be aware that it is always possible though. I am aware of that. The point is, that the function is a random but - according to it's documentation should behave identically for identical images. The idea behind this is, that you should be able to recreate the same effect on the same image - even if there is such a thing called random. The cheapest possible solution to that would be to use a constant as the random number seed. This, however, would make the random function very predictable, which I feel is horribly wrong - so I'd rather go with a hash which may collide from time to time, yet still will be a good enough seed. Torsten
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