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HP2XX, A HP-GL Converter

4.2 Adding your own formats

First, study 1. Introduction for the outline of the modular structure and general operation of hp2xx.

Let's assume you want to support TIFF format. The probably easiest way of adding new formats is by modifying copies of existing files. Since TIFF is a raster format, a good starting point would be `to_pcx.c'. (Files `to_mf.c' or `to_eps.c' should be considered in case of a vector format, and `to_vga.c' or `to_x11.c' in case of a new previewer.) Copy it to a file `to_tiff.c' and edit the latter. The old code is pretty much self-explanatory. Essentially, the output file is opened, initializations are performed, and the internal bitmap is converted into the target format (here, TIFF) scanline-by-scanline. There is just one routine called from other modules (originally named PicBuf_to_PCX. Rename it to e.g. PicBuf_to_TIFF ) and adapt the conversion code.

Once you've done that, the rest (integration of the new format into the package) is easy: First, edit `hp2xx.h' and add a prototype line for PicBuf_to_TIFF in analogy to e.g., PicBuf_to_PCX. Edit the `makefile's and add to_tiff.c to the list of sources and e.g. to_tiff.o to the list of objects. Now you are ready for compilation tests (but not for linking yet).

Then, change the main file `hp2xx.c' at various places: Near the beginning of the file, add `XX_TIFF, ' to the hp2xx_mode typedef, and a line like `XX_TIFF, "tiff", ' to the ModeList struct below. Please note the alphabetical order of these lists. Never put anything behind the termination code XX_TERM! At the end of the file, add a case statement to the switch list in analogy to e.g. the PCX entry.

You may also want to add a line to the on-line help to announce the new format, and change the release number and date. Look for functions Send_ID and usage_msg at the first quarter of file `hp2xx.c'!

Now a make all will produce code containing the new format. If your format turns out to work nicely and seems to be of general interest, please consider contributing it to the hp2xx project.