Bertho wrote: > It might be semantics but I do expect it to be practical to open a JPG and > display it, change the EXIF data and if no graphical editing was done, the > program does not need to look for how the conversion was previously done, it > just needs to read the original picture data again and then save that > unmodified data plus the new changes in the EXIF. That sounds reasonable to > me.
Bertho: No, it's not semantics. However, it's a bit more complicated than most might realize. >From a conversation I had with Marc Pawliger at PhotoPlus in 2003, my understanding is as follows. If the Jpegging was done within photoshop, and you chose to "SAVE" (not save as) the image, and only metadata was changed, then there will be no recompression of the image data. If the image data was changed, if you chose "Save As" or if you are dealing with a Jpeg that was not written in Photoshop (ie jpeg written from the camera), then the image will be recompressed. If the jpeg is saved outside of photoshop, then your guess is as good as mine. David -- David Riecks (that's "i" before "e", but the "e" is silent) http://www.riecks.com , Chicago Midwest ASMP member http://zillionbucks.com "The Webhost for your Creative Business" Chairman, ASMP Digital Photography Standards & Practices committee Chairman, SAA Imaging Technology Standards committee =============================================================== GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
