>Hi, >[EMAIL PROTECTED] (2007-11-24 at 1903.37 -0000): >> >> I'm trying to reduce noise using multiple photos of the very same subject, >using both a tripod or simply repeating a scan a number of times ( i have a >flatbed scanner with a lot of noise especially in dark areas... ) [...] >> I have used the first level, as normal, with 100% opacity, then i have added >other 9 levels ( 9 photos ), with opacity 100/9=11,1, and mode set to normal. >> >> If i use 10 levels, at 10% opacity each one, the brightness of the result is >different from the original ( lighter ). > >The trick for mixing this way is that the N layer has to be set to 1/N >opacity. >The reasoning is that the N layer will contribute that >factor, and the rest ((N-1)/N) has to come from the previous mixed >layers, so the result always totals 100% ((1 + N-1)/N). First (base) >layer 1/1 -> 100%, second layer (the one just above base) 1/2 -> 50% >(and the other 50% comes from the first), third layer 1/3 -> 33.33% >(and the other 66.66% comes from the 1 and 2) and so on. This approach >will probably have rounding errors.
Ok, thank you, works perfectly :D >> So what do you think i should use? > >Imagemagick. Simpler, faster and maybe even less rounding issues (it can add >all >images at once, then do a single multiply by 1/N, at least >that is how I would code such op). :] > >convert image1.png ... imageN.png -average result.png I have tried, but it requires more memory than i have, after 30 minutes ( with 10 images, each of 5 Megapixels ) it was still working ( 256mb ram +768 swap ), whilst with gimp everything, from loading to adjusting the opacity, took only about 3 minutes. >I investigated the topic for mixing different frames time ago to create more >film like renders (lots of other things in the trick, but >finding a fast and nice average op was one of the core issues I had to >solve): http://www.infernal-iceberg.com/blender/mblur/ I'll take a look. Thank you! ---------------------------------------------------------------------------- DEXGATEMICRO il centralino VoIP multifunzione per l'azienda. Prova gratuita per 4 utenti! Scopri tutte le funzionalita' sul sito Dexgate.com ---------------------------------------------------------------------------- _______________________________________________ Gimp-user mailing list [email protected] https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user
