Data compression in digitizing tablet

In the process of manufacture of a digitizing tablet, which uses a correction table for deriving actual stylus positions from computed stylus position, the improvement comprising:

• a) compressing the correction table, using a procedure which comprises one or more of the following steps:
• i) dividing the table into segments of containing equal numbers of elements, and compressing each segment;
• ii) using a compression technique in which a difference between a PREDICTOR and each data element is found;
• iii) subtracting a function from all data elements;
• and
• iv) testing different groupings of the elements into segments, and choosing the groupings which provide superior compression.

A procedure for manufacturing a correction table which is stored in memory in a digitizing tablet, comprising the following steps:

• a) computing position signals for each of several actual stylus positions upon the tablet;
• b) generating a correction table from which actual position can be inferred from computed position signals;
• and
• c) compressing the correction table, and storing the compressed correction in memory in the tablet.

A procedure for manufacturing a correction table which is stored in memory in a digitizing tablet, comprising the following steps:

• a) computing position signals for each of several actual stylus positions upon the tablet;
• b) generating a correction table from which actual position can be inferred from computed position signals;
• and
• c) compressing the correction table, and storing the compressed correction in memory in the tablet, whereby the correction table is divided into segments, and each segment is compressed differently.

A procedure for manufacturing a correction table which is stored in memory in a digitizing tablet, comprising the following steps:

• a) computing position signals for each of several actual stylus positions upon the tablet;
• b) generating a correction table from which actual position can be inferred from computed position signals;
• and
• c) compressing the correction table, and storing the compressed correction in memory in the tablet, whereby the correction table contains a sub-table of x-correction data, and a sub-table of y-correction data, and further comprising the step of compressing the x-correction sub-table row-by-row, and the y-correction sub-table column-by-column.

In the process of generation of a correction table for a digitizing tablet, from which actual stylus position can be derived from computed x and y values of stylus position, the improvement comprising:

• a) grouping computed values into an x-array and a y-array;
• b) deriving a mathematical function which approximates each array;
• c) for each value in each array, finding a difference between the value and the respective function;
• d) compressing the differences;
• and
• e) storing the compressed differences in the tablet.