Topic 7: Images in Electronic Publishing

Raster -v- Vector Images

BMP, TIFF, PICT, GIF (8bit – 256 colours), JPG (millions of colours), PNG    I am just starting to identify the differences between these Raster Images and the file space saving benefits within in each format.   A long way to go, but it was a useful to view the demonstration on 8 September 2010 using the ‘Mode’ function on Photshop to decrease colour depth.  The same file using the same colour depth rating was saved at 75kb as a JPG file and 15kb as a TIFF. 

I hadn’t realised that both GIF and JPG started life as corporate owned formats where as PNG has always been an open standard.  Also useful to know that a GIF file does not deteriate with compression and can be used to animate. Most webpage logos are GIF.  A JPG may detiorate.   When compressing a file usually 80% is as good enough.

Vector Images  EPS (Enscapulated Post Script), SI, SVG have to be rendered to disply on screen.  Each Vector image is ‘rasterised’ to be displayed on screen.  Flash displays Vector Images.   These images are made up of lines and curves and do not rely on resolution.   It was good to know that SVG (Scalable ventor graphics is an open-standard describing 2D graphics with XML.  Examples of colour blotching known as ‘dithering’ was clear.

The practical image editing exercise included cropping, colour brightness correction, resizing, sharpening went well.    Cloning (photoshop.com uses ‘touchup) still to be mastered and the converting to different file types particularly useful.

Flickr, Picassa and Smugmug do basic editing and worth looking as the free downloadable www.picknik.com.   Signed up for Photoshop.com.

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