There are several reasons one may wish to convert a Gerber photoplot file back to GDSII. For example, you may wish to use IC lithography equipment to create a photomask -- such equipment generally requires CAD data in GDSII Format. Or you may wish to take advantage of tools such as XOR comparison that is commonly available for IC masks. This app note explains how to use Artwork's gbr2gds engine from a command line (bypassing the user GUI).
RS274D vs RS274X
There are two types of Gerber files we must deal with: the original RS274D file format which goes back 30 years and the newer RS274X format which contains all required plotting information embedded into the file header. Since GBR2GDS was written back before RS274X was popular, it does not read the newer format directly. Instead one has to run a utility that will create job and apt files for the converter.
Before converting an RS274X file to GDSII we must run the utility called rs274xjb on it which will produce two resource files needed by the converter.
the command line syntax is:
rs274xjb <gerber_files> -job jobfile -apt aptfile where rs274xjb 274X scan utility gerber_files a file or files (if more than one use a wildcard specification) to be scanned. -job jobfile name of the .job file to be produced -apt aptfile name of the .apt file to be produced
Contents of the Job and Apt File
We ran the utility on a simple one layer Gerber file called TOP24.gbr
rs274xjb TOP24.gbr -job reverse.job -apt reverse.apt