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     Most, if not all, of the images you see on the Internet are raster images. Raster images are composed of small points of color data called pixels (short for "picture element"). The advantage of raster images is the ability to represent complex shapes and colors in a relatively small file format. Photographs, for example, are represented using raster images.
     The raster image on the right has a width of 173 pixels and a height of 276 pixels. This image is restricted to these dimensions. In other words, resizing this image would produce distortion. If you were to zoom in using image editing software, you would be zooming in on individual pixels; the image would get "blocky" and detail become substantially less sharp. This is a phenomenon referred to as "pixelization." See illustration below.

  Because of the dimensional restrictions, printing a raster image larger than your paper size (legal, letter, etc.) is inefficient.

Raster Images Used on Alabama Maps

     All of the maps in the Contemporary Map Index are available as a JPEG (.jpg) download. If you wish to view our maps only on your screen (and not print them), then JPEG files are the best option to choose. Our maps in this section are at a sufficiently high DPI (dots per inch) to be viewed in detail without the need to zoom.

     Maps in the Historical Map Archive are in MrSID format, a "wavelet" compression format designed to store large images for viewing on the Internet. MrSID functions by decompressing only the section of the map you are interested in (zoomed into). As such, you may only print or save (accessed via right clicking on the image) the part of the image you are currently viewing. If you require the map printed in its entirety, submit a quote request and we will respond with the cost to reproduce the map.


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