The Little Guy Posted July 25, 2009 Share Posted July 25, 2009 How does "History" work in photoshop? When you have an image, and you press "Undo" how does it know what to undo? Or redo? The only thing that I can think of, is that photoshop would save a version of the image, every time an edit has been done, so every time the image changes it saves a copy of the previous image. Quote Link to comment Share on other sites More sharing options...
cs.punk Posted July 25, 2009 Share Posted July 25, 2009 How does "History" work in photoshop? When you have an image, and you press "Undo" how does it know what to undo? Or redo? The only thing that I can think of, is that photoshop would save a version of the image, every time an edit has been done, so every time the image changes it saves a copy of the previous image. Or maybe only 'certian elements'. As if you have applied a effect it's hard to get the original with 'de-effecting it' lol Quote Link to comment Share on other sites More sharing options...
waynew Posted July 25, 2009 Share Posted July 25, 2009 It seems to make a log of all the lastest actions you've carried out and then reverses those actions when you hit undo. Quote Link to comment Share on other sites More sharing options...
The Little Guy Posted July 25, 2009 Author Share Posted July 25, 2009 OK, yeah, but you have your current edit, how does it know what the previous edit looked like when you press undo? Quote Link to comment Share on other sites More sharing options...
nrg_alpha Posted July 25, 2009 Share Posted July 25, 2009 OK, yeah, but you have your current edit, how does it know what the previous edit looked like when you press undo? Probably by examining the previous action / state and reverting back to it. Every brush stroke, marquee selection, pixel plot, etc.. is stored. The longer you work on something, the larger the file gets. Once in a while, you can use the purge command to alleviate this. I wouldn't bust my head over the extreme technicalities of how it works.. I for one am grateful for Ctrl + Alt + z to continuously undo things, or Ctrl + Shift + z to march through redos (in the event I go back to far). I don't make use of the actual History palette personally. Quote Link to comment Share on other sites More sharing options...
The Little Guy Posted July 27, 2009 Author Share Posted July 27, 2009 I am basically trying to think of a way I could implement this technology into a smaller graphics application I am trying to make using ImageMagick Quote Link to comment Share on other sites More sharing options...
waynew Posted July 28, 2009 Share Posted July 28, 2009 Log every action and make sure that every action can be reversed. The image will take care of itself. Quote Link to comment Share on other sites More sharing options...
MadTechie Posted July 28, 2009 Share Posted July 28, 2009 It doesn't truly work by reversing the action history alone, simple actions like drawing lines etc do work that way buy more complex actions like rasteration and re-sampling, create a flag in the actions script that as a link to the a re-storable copy, (a backup if you will) the reason for this is simple, if you have a image 1024x768 and resize it down to 1x1 then resize it back to 1024x768.. its not going to look the same! with that in-mind to you could simply create a backup before any action then the undo just restores back to save space use fifo with 20 actions history. Quote Link to comment Share on other sites More sharing options...
jcombs_31 Posted July 28, 2009 Share Posted July 28, 2009 if you have a image 1024x768 and resize it down to 1x1 then resize it back to 1024x768.. its not going to look the same! Unless you create a smart object Quote Link to comment Share on other sites More sharing options...
rhodesa Posted July 28, 2009 Share Posted July 28, 2009 if you have the original image, and the list of commands run on that image to reach the current image, you can always go back in time by just reverting to the original image and re-applying the actions up to the point where you want to revert to Quote Link to comment Share on other sites More sharing options...
MadTechie Posted July 28, 2009 Share Posted July 28, 2009 Nice idea, rhodesa but your need to store every action from the start which means some heavy actions at the start going make a simple line undo quite long.. in any case theirs lots of pros and cons to each. as for smart objects.. yes very true but i don't think ImageMagick supports them Quote Link to comment Share on other sites More sharing options...
The Little Guy Posted July 29, 2009 Author Share Posted July 29, 2009 I like your ideas! Saving a copy before each revision, is the same as my idea, but using an original image, and have a "Macro" like history could be a good idea too! I like both the ideas, I think I may use them both! Any other ideas is appreciated! Quote Link to comment Share on other sites More sharing options...
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