Compare the relative advantages and disadvantages of bitmap and vector image types.

In any computer graphics industry, it is vital to understand the differences between bitmap and vector images (Leurs 2012).

A bitmap image is a matrix of pixels, where each individual pixel is assigned a colour value (Leurs 2012). For a photograph, a 3D render or a highly detailed drawing, this pixel based format excels at describing very subtle changes in tone, especially where photo-realism is the desired result. The number of pixels contained in a bitmap is referred to as the ‘resolution’. This resolution is determined by the device which captured the image, whether it be a digital camera, a scanner, or maybe a render output from a 3D software package.

The resolution choice is dependent on the intent. Less resolution is required when viewing the image on an RGB monitor than when printing to a substrate. This is because a computer monitor displays somewhere in the region of 70 to 100 pixels per inch (or DPI) as opposed to printing, which requires between 150 and 300 DPI so individual pixels will not be discernible to the naked eye.

Another factor used to determine resolution for print is the intended viewing distance. A billboard, for instance, is viewed from a far greater distance than a magazine and hence requires a lower DPI. So the necessary resolution can vary vastly depending on the purpose, from say 32 x 32 pixels for an on-screen desktop icon to 9600 x 9600 for a large outdoor advertisement to be viewed at close range. The disadvantage with these higher resolutions is that the file size is often large. This can hinder the performance of processing and also transferring of images.

Re-sizing of a bitmap post-capture is possible, by either reducing or increasing the number of pixels in an image. This function, called interpolation is performed using image-editing software such as photoshop, though is best kept to minimum as it may introduce aliasing or visible stepping on edges. One convenience of bitmaps is the ease of creation. Anyone who has taken a digital photograph has created a bitmap.

Usually associated with simple cartoon-like drawings, logos, maps etc. vector images are defined using mathematical equations rather than pixels. Formed via a series of shapes, straight lines and curves, these vector paths or beziers contain attributes such as colour fills and outlines that contribute to the appearance of the image (Chastain 2012). These fills and strokes are not limited to single colours and can, in fact, be complex mathematical gradients.

Vectors are accurate for describing simple forms containing compartmentalized blocks of colour and tone. They are small in file size, requiring tiny amounts of disk space compared with bitmaps. They are also infinitely scalable or resolution independent and can be rotated or scaled infinitely with no loss in detail or sharpness. This flexibility makes vectors ideal for company branding where the imagery has to go across a wide range of media from envelopes, letterheads and business cards to a sign that may be printed across the front of a building. A downside of vector images is that they are more complex to create and some knowledge of the graphic design process is required.

One way to benefit from the advantages of both vectors and bitmaps is to use metafiles which can combine the two. The most commonly used kind of metafile is the Adobe PDF format (Chastain 2012).

Laurens Leurs, 2012, Bitmap versus vector graphics, prepressure.com, accessed 21st June 2012, <http://www.prepressure.com/library/file-formats/bitmap-versus-vector>.

Sue Chastain, 2012, Vector and Bitmap Images, about.com, accessed 12th April 2012, <http://graphicssoft.about.com/od/aboutgraphics/a/bitmapvector_2.htm>.

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