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C.2 Converting GMT PostScript to PDF or raster images

Since Adobe's PDF (Portable Document Format) seems to become the de facto standard for vector graphics, you are often well off converting GMT produced PostScript files to PDF. Being both vector formats (i.e., they basically describe all objects, text and graphics as lines and curves), such conversion sounds awfully straightforward and not worth a full section in this document. But experience has shown differently, since most converters cut corners by using the same tool (Aladdin's ghostscript) with basic default options that are not devised to produce the best quality PDF files.

For some applications it is practical or even essential that you convert your PostScript file into a raster format, such as GIF (Graphics Interchange Format), TIFF (Tagged Image File Format), PNG (Portable Network Graphics), or JPEG (Joint Photographic Experts Group). A web page is better served with a raster image that will immediately show on a web browser, than with a PostScript file that needs to be downloaded to view, despite the better printing quality of the PostScript image. A less obvious reason to convert your image to a raster format is to by-pass PowerPoint's rendering engine in case you want to embed the image into a presentation.

The are a number of programs that will convert PostScript files to PDF or raster formats, like Aladdin's pstopdf, pbmplus' pstoimg, or ImageMagick's convert, most of which run ghostscript behind the scenes. The same is true for viewers like ghostview and Apple's Preview. So a lot of the times when people report that their PostScript plot does not look right but prints fine, it is the way ghostscript is used with its most basic settings that is to blame.



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Next: C.2.1 When converting or Up: C. Including GMT graphics Previous: C.1 Making GMT Encapsulated   Contents   Index
Paul Wessel 2008-05-15