Unit 1


unit 1

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Types of graphics

There are two main types of digital image format. These are bit map (raster) and vector images.


Bit map images are made up of many dots called pixels. Images taken on digital cameras are saved as bit maps. Bit maps are resolution dependent. Resolution refers to the number of pixels in an image and is usually stated as dpi (dots per inch) or ppi (pixels per inch). Bit map images are displayed on your computer screen at screen resolution: approximately 100 ppi. However, when printing bit maps., your printer needs much more image data than a monitor. In order to render a bit map image accurately, the typical desktop printer needs 150-300 ppi. When resized bit map images begin to blur. Examples of bit map image formats are jpeg, gif and png.


Vector images are made up of lines. When resized vector images do not lose quality as mathematical calculations are completed to reproduce the lines either larger or smaller resulting in no pixilation. Clip art images (usually saved in the .wmf format) are examples of vector graphics.



Further Reading

Image formats on Wikipedia




Anthony Bennett


Software Tutorials

photoshop iconCropping your images

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