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HP2XX, A HP-GL Converter

2.6 Raster formats

Raster graphics are probably the most widely used graphics by now. Many publishing programs accept rasterized graphics. It's likely you'll use hp2xx primarily in some raster mode.

In addition to vector modes, all raster modes need the desired resolution of an assumed underlying pixel grid to plot on, i. e., the number of pixels per unit length within that grid. A traditional measure is the number of "dots per inch" (DPI). hp2xx makes an exception from its usual unit length mm and lets you specify the traditional DPI values. Option `-d num' affects both x and y direction, num being the DPI value (an integer). if `-D num_y' is also specified, num_y will override the num DPI value, but only for the y direction.

Some programs were found, which generate HPGL output with too tight clipping bounds, which lead, for example, to some parts of text characters clipped off. Use option `-e num' to add some extra amount of space to clip areas to work around such problems. For example, `-e 40' will add 40 extra plotter units to every side of the clipping box, which corresponds to 1 mm in true size.

There are plenty of raster formats on various platforms, much more than hp2xx will ever handle. The supported raster formats IMG, JPG, PBM/PPM, PCL, PCX, PNG and TIFF were chosen for their widespread use, their simplicity, for actual demand, and for accessibility of specifications. If your desired format is not supported, look for a converter. E.g., the Portable Bitmap (PBM) project and more recently, the ImageMagick package offer quite a variety of such converters.

Please note that the preview mode (which does not create any output file) is a special raster mode. Instead of going into some output file, the internal bitmap is transferred into display memory. Therefore, the above considerations apply also to preview mode.