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 Photoshop CS3 Scripting Basics     11

The 

Application

 class is the root of the Photoshop CS3 object model hierarchy. Scripts must target the 

appropriate application in order to run correctly. See 

.

The 

Document

 class is used to make modifications to the document image. By using the 

Document

 object 

you can crop, rotate or flip the canvas, resize the image or canvas, and trim the image. You could also use 
the 

Document

 object to get the active layer, then, save the current document, and copy and paste within 

the active document or between different documents. For more information on using document objects, 
see 

 and 

.

Photoshop has two types of layers: an 

Art Layer

 that can contain image contents and a 

Layer Set

 that 

can contain zero or more art layers.

An 

Art Layer

 is a layer class within a document that allows you to work on one element of an image 

without disturbing the others. Images are typically composed of multiple layers, defined by a 

Layer Set

. 

You can change the composition of an image by changing the order and attributes of the layers that 
comprise it.

A 

Text Item

 is a particular type of art layer that allows you to add type to an image. In Photoshop, a 

Text 

Item

 item is implemented as a property of the art layer. For more information on text items, see 

A 

Layer Set

 is a class that comprises multiple layers. Think of it as a folder on your desktop. Since folders 

can contain other folders, a layer set is recursive. That is, one layer set may call another layer set in the 
Object Model hierarchy.

For more information on layers, see 

The 

Layer Comp

 class allows you to create, manage, and view multiple versions of a layout within a single 

document. 

The 

Channel

 class is used to store pixel information about an image’s color. Image color determines the 

number of channels available. An RGB image, for example, has four default channels: one for each primary 
color and one for editing the entire image. You could have the red channel active in order to manipulate 
just the red pixels in the image, or you could choose to manipulate all the channels at once.

These kinds of channels are related to the document mode and are called component channels. In addition 
to the component channels, Photoshop lets you to create additional channels. You can create a spot color 
channel, a masked area channel, and a selected area channel.

Using the commands or methods of a 

Channel

 object, you can create, delete and duplicate channels. You 

can also retrieve a channel's histogram, change its kind or change the current channel selection.

For more information on channels, see 

.

The 

Selection

 class is used to specify an area of pixels in the active document (or in a selected layer of the 

active document) that you want to work with. For more information on selections, see