CREATING A DIGITAL FILE: Details

IMAGE FILE FORMATS

Your image editing or scanning software allows you to save images in a variety of file formats. With so much variety, how do you know which file type suits your needs?

Basically, there are three types of graphics file formats: bitmap, vector and metafile. Pictures created as rows and columns of pixels are generally referred to as bitmap files. Each pixel is assigned a particular colour or gray value and the combination of all of the pixels make up the image. Image editing programs such as Adobe PhotoShop®, or the software you use to run a scanner, are some of the more common applications for creating bitmaps. TIFF (tag image file format), BMP (Windows bitmap), MacPaint®, and PCX are all examples of bitmap-format graphics files.

Another type of file format commonly used is the vector-based file format. Vector-based files contain mathematical instructions for drawing objects. These expressions describe shapes such as lines, ellipses, polygons, rectangles, and arcs. Simply put, the vector file gives the instructions, "Start this line at point A and draw to point B" or "This is a polygon made up of the following line segments." PostScript paths and type, such as those you’d find in an Illustrator EPS (Encapsulated PostScript) file, are examples of vector-format graphics files.

The third popular format is called a metafile. Metafiles may contain both vector and bitmap graphics, but don’t necessarily have both - sometimes you’ll find metafiles that contain only an image. Macintosh PICT®, Adobe Illustrator®, EPS, CGM (Computer Graphics Metafile), and WMF (Windows Metafile) formats are all examples of metafiles.

For files being sent to Webcom, make sure to use EPS for vector-based graphics and TIFF for bitmap images.

GIF or JPEG formats are only appropriate for viewing on screen - on the Web or in multimedia presentations. If you’ve ever printed pictures from a web site, you probably noticed that the low resolution nature of the graphics resulted in a poor quality print-out.

Most professional programs allow you to convert files from one format to another. Look for a Save As, Save a Copy or Export command.

GRAPHIC FILE CONVERSION CHART
DXF, vector metafiles, or metafiles with bitmap and vector elements		EPS
PCX, BMP, or bitmap metafiles		TIFF

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