1. A compressing apparatus for compressing pattern data, the pattern data including a first number of first dot data having a value "0" and a second number of second dot data having a value "1", said compressing apparatus comprising: increasing means for increasing the first number of the first dot data in the pattern data to provide modified pattern data; and encoding means for counting, in the modified pattern data, a first counted value indicating a number of continuous first dot data so as to generate a first code having an operand indicating a range for the first counted value and a data portion indicating a relative value of the first counted value in the range, said encoding means further counting, in the modified pattern data, a second counted value indicating a number of continuous second dot data so as to generate a second code indicating the second counted value, said encoding means encoding the modified pattern data by alternatively using the first and second codes.