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Map Room Home page | |
written by Nigel
James
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MAPINFO How to... | |
No. 18: Saving your map as an image file | |
(References to tables, folders etc., are not applicable outside the Map Room, so if you are located elsewhere, you should substitute your own) | |
Maps created in MapInfo are normally printed from MapInfo itself. This ensures a high-quality output. However you may wish to use your map(s) in other applications, such as Powerpoint, or in documents created in a Word, etc. This How to guide explains how to get the best results. It is assumed that you know how to create maps. See MapInfo How to No. 1 if you require more information on this. |
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IMPORTANT | |
Maps created in MapInfo in the Map Room can only be usd for teaching and research purposes. Limited publishing is allowed in certain cases, but images may NOT be used on web pages. Please ask in the Map Room for further information. | |
Maps created in MapInfo are normally printed as layouts, where you can include titles and other details and perhaps additional maps showing location etc. If you wish to insert the maps as images in a document, then you can save your maps as image files by using the Save Window As… option in the File menu. |
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Save the individual maps or the layout? You can save a layout as a single image, which include the title and other text, legend and any other items. This may not necessarily be the best choice, as it may be too large for your document or you may wish to arrange the maps and legends etc., in a different way. The alternative is to save each map (i.e. the mapper windows) as a separate file, together with the legend window, if present (it is a mapper window as well). You can then arrange the separate images how you wish in your document. |
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What file format should I use? An image can be saved as a raster file, which is just like a scanned image, or as a vector file, which is sizeable - the usual format is Windows metafile (.wmf), which is compatible with Word and other Windows software. As a guide, if you are using the images to display on screen (e.g. in a PowerPoint presentation or on a web page), then save them as raster files. If you are using them in a document, save them as metafiles. |
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What is the difference between raster files and metafiles? |
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The print quality of a raster image is determined by its
resolution. This is calculated as the number of pixels per inch (or dots
per inch for the printed image). An image for display on screen has a
resoluton of around 72 pixels per inch. This means that when the image
is used in PowerPoint for example, it will appear at the same size as
it was in MapInfo. If an image is printed at this resolution however,
it will appear coarse as the pixels will be clearly visible, as can be
seen in fig. 1. To avoid this, the image resolution has to be much higher
and this will be explained further on. A metafile on the other hand, is
not an image at all, but a set of instructions describing the image. This
means that the image can be resized without loss of quality as there are
no pixels - the image is created from the instruction set at the size
required. Also the symbols, lines and text stay the original size. This
is why a metafile is better for documents.
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Saving the map as a raster image for use on screen
in presentations etc.
Open the File menu and click Save Window As… |
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In the Save Window As… dialog, select the Same as Window option
if you will be using the image at the same size as it currently appears
on screen. Alternatively, select Custom size and enter the size
required (the width and height are linked, so changing one automatically
changes the other) Leave the Resoution as 72. |
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Next, click the Advanced button and you will have the choice of including a border, which can be selected by clicking the appropriate checkbox. Leave all other options checked and click OK. Now click the Save… button. |
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Which raster format should I use?
To minimise file size, save the image as a JPEG (.jpg) file. JPEG files are compressed, but at a cost of slight loss of image quality. This is not noticeable when displayed on screen, so for display use such as in PowerPoint JPEG format is fine. |
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Warning! A JPEG file is compressed each time it
is saved, so if you open your file and then save it again, the image is
further degraded. If you intend editing your image in imag editing software,
save it in an uncompressed format to work on it (such as TIFF). When you
save the final version, use JPEG again, but set the compression to minimum
(check how to do this in your editing software).
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Saving the image for use in a document
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For images which are to be included in documents, metafiles
are the better option. Resolution is not a problem as the image is scaleable
(just like the maps are in MapInfo itself). File sizes are generally
smaller and so easier to transfer, but the size is dependent on the number
of map objects and their complexity, so file size can be very large for
maps with complex line and polygon features. To save your map as a metafile,
follow the same steps as for raster images, but choose Windows metafile
(.wmf ) as the file format. This is compatible with Word and other
Windows software. The other metafile option, Windows Enhanced Metafile
(.emf) has additional features which are not needed to save MapInfo images,
so use the normal .wmf format. Remember that although your image is in
vector format (the same as MapInfo), it is a single layer so features
cannot be deselected. However it can be edited in a suitable drawing program.
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A couple of points to remember when exporting as metafiles:
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Do not use the halo effect on text or symbols if you are saving your map as a metafile. You may find that some printers will only print the white halo and not the text or symbol. Also, you may find that if you export the map and legend separately, there are slight differences in the colours (the legend colours may not match exactly with the map). If this happens, export the map as a single image by saving the layout window instead. |
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Saving images in raster format for use in documents | |
If you are using MapInfo version 7.0 or later, the resolution should be increased to 300 dpi to maintain image quality. If you are using version 6.5 or earlier, you do not have the resolution option, so to achieve the increased image quality, you need to save the image at around three times the size it will appear in your document. When it is sized down to fit the document, the resolution will increase. Unfortunately this method results in text and symbols one third their size and so theymay be unreadable. To avoid this, change the font and symbol size before saving the file (e.g. increase 8 point font to 24 point). It will appear far too large on screen but will be correct in the printed image.The same correction can be applied to lines and symbols if required. The quality loss in JPEG format can be noticeable (slightly blurred text), so an uncompressed format such as TIFF is preferable, but file sizes are considerably larger. | |
This is a brief and specific guide to
this topic, for more general information, see:
MapInfo l - an easy guide for new users
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Nigel
James
Bodleian Library 2003 |