How to place several copies of a picture?
The picture can be a sampled image or EPS file. PostScript always reads the standard input stream forward. There is no way to reposition the file or push characters back. Next picture need a new copy of data. To reuse the picture we need to copy the data from the input stream to the reusable object. Short data can be stored in a PostScript string, but the string length is limited to 64K-1 . More data can be stored as an array of strings. The length of array is also limited to 64K-1 but this is enough to exhaust the memory on most printers. In fact low end printers can have as little as 256K of free memory. Encoding filters can be used to compress picture data. In level 3 PostScript most encoding filters are optional. PostScript level 3 introduces reusable streams. They cache the input data and can be repositioned after reading to the end of the file. On disk-less printers reusable streams are implemented in memory file system. Some printers and most host-based RIP’s have writeable file
