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Photoshop

Digital Graphics

Bitmap Graphics

Computers display two different types of digital images: bitmap (also called raster) and vector. Understanding the differences between the two will enable you to optimize the performance of your Web pages. [Note: Use of the term bitmap shouldn't be confused with the .BMP (bitmap) Windows image format, which is not a Web standard. We'll use 'bitmap' as a generic term that includes all file types that format images using pixels. In this and the next few lectures, we'll be talking a lot about bitmaps because this is the digital image format used by Photoshop.

bitmap image	detail magnified 800% showing pixels

Image Pixels

Like monitors, bitmap images are composed of pixels. In a digital image pixels are tiny squares of colour arranged in rows and columns as though on a grid. Image pixels are shown in the picture at the right, above. Each pixel contains a single colour. In the previous lecture we said that one image pixel needs one monitor pixel to display it. Because of this, bitmaps are referred to as 'resolution-dependent'.

Bitmap File Formats

Bitmap images are the most common type of file. The main benefit of bitmap images is that photographic colour, tone, and textures are accurately reproduced. Examples of bitmap image formats include GIF, JPEG, PNG, PSD (Photoshop), TIFF, and BMP. Bitmap formats that are acceptable for use on the Web are JPEG, GIF, and PNG. The two that you will use for your Web pages will usually be GIF or .JPEG. We will describe each in more detail later.

Bitmap Graphics Summary

• There are two different digital image types: bitmap (or raster) and vector.
• Bitmap graphics are composed of pixels which are tiny squares of colour.
• Bitmap graphics are resolution-dependent.
• Bitmap file types used on the Web are usually JPEG or GIF.
• Bitmap images are the most common image type on the Web right now.

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Photoshop - TOC - Introduction - Books -
Digital Graphics - Links - Questions -
1 - [ 2 ] - 3 - 4 - 5 - 6 - 7 - 8 - 9 - A -

Photoshop - TOC - Introduction - Books -
Digital Graphics - Links - Questions -
1 - [ 2 ] - 3 - 4 - 5 - 6 - 7 - 8 - 9 - A -