Bitmaps and Vectors

Photoshop is an image-editing application with of tools and commands for working on digital images or bitmaps. there are ultilities for retouching, colour correcting, compositing and more. There are also over 90 functional and creative filters that can be applied to entire images, or selected areas within images.

A bitmap image consists of a rectangular grid, or raster, of pixelsin concept, very much like a mosaic. when you edit a bitmap you are editing the colour values of individual pixels or group of pixels.

Image-editing applications differ fundamentally from vector-based applications such as
Adobe Illustrator and Macromedia Free Hand. In these applications, you work with objects that can be moved, In these applications, you work with objects that can be moved, scaled, transformed, stacked and deleted as individual or grouped objects, but all the time each exists as a complete, separate object.

These applications are called vector drawing packages, as each object is defined by a mathematical formula. Because of this, they are resolution-independent-you can scale vector drawings up or down (either in the originating application or in a page layout application such as QuarkXPress or Adobe Page Maker) and they will still print smoothly and crisply.

In contrast, bitmaps are created at a set resolution-a fixed number of pixels per inch. If you scan an image at a specific resolution (unless you add more pixels). You are likely to end up with a blocky, jagged image, as you have increased the size of the individual pixels that make up the bitmap image.

NOTE- You should always try to scan an image at, or slightly larger than, the size at which you intend to use it. This means you will avoid having to increase the size of the image.