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Introduction
Adobe Photoshop is a hybrid application, not only can it handle raster information (pixels), it can also hold path information (vector). Photoshop stores raster information in the Layers palette, and stores vector information in the Paths palette. When you use Photoshop's vector drawing, or pen tools, Photoshop creates a path in the Paths palette to store that information. In addition, it is possible to create a selection with Photoshop's traditional selection tools, and convert that selection into a path. Paths are defined mathematically using anchor points and segments. Once created, they can be precisely modified to fit any design situation. In many ways, paths serve a function similar to channel masksthey can define selections, but because they're vector and not raster, they are much more precise. When paths are saved they take up far less room than channels.Working with the various Pen tools, it's possible to create precise paths, and even create complicated selections around virtually any shape. Once the path is created it's a simple matter to subtract anchor points, and add new or modify existing anchor points to produce complex paths. It's even possible to convert straight segments (the visible line that connects two anchor points together) into elegantly curved segments, or you can remove the curve from a segment with a single click of the Convert Curve tool. Paths can be used to precisely guide a brush stroke, or the interior of a path can be filled with any color, pattern, or gradient available in Photoshop using the Stroke and Fill Commands. Paths can even be used to create a clipping path around an image. When moving an image into a layout program, such as InDesign, a clipping path lets you define certain areas of an image as transparent. In addition, you can create paths in Photoshop, then export and open them in Adobe Illustrator. Using Photoshop paths give you precise, mathematical control over the creation of complex shapes, selections, and even transparency.
Understanding Vector and Raster Images
Photoshop is a hybrid application that gives you great control over photographic (raster) images, and seamlessly combines that with the elegance and form of artistic (vector) shapes. When you work on the raster side of Photoshop, you're dealing with an image that is a visual brick wall with each brick (or pixel) identifying one piece of color information. The reason raster images are considered resolution dependent is that once the image is created or scanned, any enlargement of the image forces Photoshop to enlarge and average the existing color information in the document.This process, called interpolation , is what causes enlarged raster images to become blurred, or pixilated. Vector images are created using mathematical shapes, not pixels, and that's why vector shapes are considered resolution independent. For example, if you enlarge a vector image to 100 times its original size, Photoshop merely changes the mathematical formulas to coincide with the new size, and since vector shapes are constructed of math not pixels, file sizes are extremely small.
