PGM: 1/O and Polymorphism The purpose of this assignment is to continue practicing inheritance and polymorphism in Java. PGM Image Format The PGM (or Portable Gray Map) image format is encoded in human-readable ASCII text. For those of you found here. Sample PGM File: who wish to have the experience of reading real documentation, the formal image specification can be P2 24 7 15 0 3 0 0 0 0 0 7 0 0 0 0 0 11 0 0 000 15 0 0 15 0 0 3 0 0 0 007000 00 11 0 000 0 15 0 0 00 Image Header Looking at the sample PGM file above, P2 is a "magic number". It indicates what type of PGM (ASCII encoding) image this is. For this assignment it will always be P2. Next comes the number of columns and the number of rows in the image (24 x 7). Finally, we have the maximum color value 15. This can be any value, but a common value is 255. The way you see the header presented is how it should be spaced out