Report On The Data Structures Used In Photoshop

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Adobe Photoshop is a raster graphics editing application developed and published by Adobe Inc.

In the Photoshop application, the history buffer can store a maximum 20 entries because each editing operation may require a large memory space to be stored.

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Problem Definition

In our world where almost, everyone gets attracted by what they see, it has become very important that companies, individual firms and people who wish to advertise their products and even events have a very nice and creative impression of what they want to sell out so as to get more people to patronize their goods and services.

Hence to make such impressive and appealing designs, Adobe Inc. created Photoshop to save the day. Nevertheless, when we are not able to reverse wrong actions taken during the design process, that would another big problem. Since with a little mistake, one would have to restart the design process all over again making the whole process time-consuming. And in that case, such works would require top notch professionals to bring out something very nice in a short time.

The solution to the Problem

So, to solve the problem of being able to reverse wrong actions taken during the design process, it has become imperative that stacks are used.

Stacks and queues are mostly used as programmer’s tools. They’re primarily conceptual aids rather than complete data storage devices. Their lifetime is shorter than that of the database-type structures.

They are created and used to carry out a task during the operation of a function within a program; when the task is completed, they’re discarded.

Items can be equally pushed and popped from a stack in constant, thus, O(1) time. That is, the time is not dependent on how many items are in the stack and is therefore very quick.

The Role of Stacks in Photoshop

Just like word processing applications and other editors, Photoshop also incorporates the undo and redo operations.

Undo is an interface practice which is employed in many computer programs such as word processing application and editors. It removes the latter change done to the document returning it to a previous state. Redo on the other hand, is the reverse of undo. It allows you to go back to a more current phase of your work.

To implement this undo and redo operations in Photoshop, stacks are used. Two different stacks are created;

  • One to keep track of the history of every single activity performed in the program, and it is often called the Undo stack.
  • The second stack is the redo stack. It holds the breadcrumbs back to the initial state before a user starts undoing.

So, as the user does something in the application say, crops an image, blurs an image, colors an image, and so on, every action is PUSH (ed) onto the undo stack in the order in which they were performed such that, the last action performed is the first action to be undone.

If the user undo’s an action by clicking a button, it’s POP (ed) off the undo stack, do the operation, then the action is PUSH (ed) onto the redo stack.

If the user undo’s multiple times, then, it does not redo but instead performs a unique action, thus the redo stack is considered stack lost.

Most often than not, undo is always accessible until the user undoes all performed operations back. However, there are some activities which are not kept in the undo list and so there’s no opportunity to undo these. For example, saving file is not “undoable”, but is enqueued in the list to show, that this command was executed. One more action, which is not “undoable” and not stored, is scrolling or selection.


So, we have seen that using the data structure stacks in Photoshop and other editor makes it easier to use in the sense that, it is always possible to revert changes made to a document while it’s still on the undo stack. This goes a long way to make beginners explore new ideas without any fear of making mistakes.

Also, since the undo and redo operations occur in a constant time O(1), it does not waste a lot of precious time making it easy to go with.


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