Unlimited Undo/Redo PictureBox

[cyborg]

Hi!

I have a problem...

I love to make painting programs and other graphic programs, and now i want to make an unlimited undo/redo function, but i dont know how!

I've tried to remake a function for richtext but it didnt turn out good

please help me! i really need to know how to do this!

[SLH]

One way would be to store the previous and new value of each pixel as the user changes it. Then wien the user clickes undo, have it revert (but you would have to work out how to undo, i.e. don't have to undo each pixel individualy).


I havn't tried doing an undo feature but i woudl suggest something like this.

Create an array of a custom type like this

Private Type typUndoRedo
    PixelX as Double
    PixelY as Double
    OldColour as Long '???
    NewColour as Long '???
    IsUndoRedoPoint as Boolean
End Type
Dim UndoRedo(Really Big Number, Or variable length) as typUndoRedo

I presume you have various functions for manipulating pixels, such as square, circle, line etc....

Do this sort of thing for each of these.

sub Box(param1,param2...)
    'The first pixel change
    currentnumber = currentnumber+1
    UndoRedo(Currentnumber).isundoredopoint = True
    UndoRedo(Currentnumber).pixelx = 5
    UndoRedo(Currentnumber).pixely = 7
    UndoRedo(Currentnumber).OldColour = ColourOfPixel(5,7)
    UndoRedo(Currentnumber).NewColour = vbBlack
    pset (5,7),vbBlack
    
    'The rest of the code for changing all the pixels in the square
    currentnumber = currentnumber+1
    UndoRedo(Currentnumber).isundoredopoint = False
    UndoRedo(Currentnumber).pixelx = X
    UndoRedo(Currentnumber).pixely = Y
    UndoRedo(Currentnumber).OldColour = ColourOfPixel(X,Y)
    UndoRedo(Currentnumber).NewColour = vbBlack
    pset (X,Y),vbBlack


    'The Last Pixel Change

    currentnumber = currentnumber+1
    UndoRedo(Currentnumber).isundoredopoint = True
    UndoRedo(Currentnumber).pixelx = 56
    UndoRedo(Currentnumber).pixely = 32
    UndoRedo(Currentnumber).OldColour = ColourOfPixel(56,32)
    UndoRedo(Currentnumber).NewColour = vbBlack
    pset (56,32),vbBlack
end sub

Now, for your undo function, you will start at currentnumber, and go back through the array, changing the pixels to oldcolour. UNTILL you get to the isundoredopoint = True

For the redo function you would do the same, but go forward.



NB: This is purely, me thinking about how it may work, as i havn't tried it before, or tested the above method it may not work. Its just an idea of how i would go about it. Hope it helpes.

If you want me to explain a certain aspect better, just ask.

[cyborg]

i think i get the idea but im not a good programmer so i would need some help to finish it...

one think that would be cool is to make a listbox with thumbnails of the changes so the user could click on any item in the list to restore a previous picture...
i think phososhop has that feature but im not sure....

[SLH]

You start it, and i'll be happy to help.

Unless you did some clever coding, to manipulate those pictures, that would take up A LOT of memory, with a lot of undo levels.

[Hack]

Download the project attached in this thread to the last post by Nucleus.

http://www.vbforums.com/showthread.p...highlight=undo

[cyborg]

oh! thanks!
that code reminds me alot about that richtext undo/redo code that i couldt remake to picturebox code, but i can try...