Methods of and apparatus for encoding and decoding data

A method of encoding a texture map for use in a graphics processing system, the method comprising:

• dividing a texture map to be encoded into a plurality of blocks of texture data elements;
• and
• for each block of texture data elements:
• determining at least one direction in the data space to be used when determining a base data value or values to be used when encoding the block of texture data elements using the method of any one of the preceding claims;
• using the at least one determined direction in the data space for the block of texture data elements to derive at least one base data value to be used when encoding the block of texture data elements;
• and
• encoding the block of texture data elements as a block of texture data representing the block of texture data elements using the derived at least one base data value.

An apparatus for determining for a set of texture data elements to be encoded for use in a graphics processing system, a direction in the data space of the texture data elements to be used when determining a base data value or values to be used for the set of texture data elements when encoding the set of texture data elements, the apparatus comprising:

• processing circuitry configured to:
• determine, for at least one plane that divides the set of texture data elements to be encoded into two groups in the data space, the direction of a vector in the data space from a point in the data space that is based on the values of texture data elements of the set of texture data elements to be encoded whose values lie on one side of the plane in the data space to a point in the data space that is based on the values of texture data elements of the set of texture data elements to be encoded whose values lie on the other side of the plane in the data space;
• and
• use the direction determined in the data space of the texture data elements for at least one of the at least one planes that divide the set of texture data elements into two groups in the data space to determine a direction in the data space to be used when determining a base data value or values to be used for the set of texture data elements when encoding the set of texture data elements.

An apparatus for encoding a texture map for use in a graphics processing system, the apparatus comprising:

• processing circuitry configured to:
• divide a texture map to be encoded into a plurality of blocks of texture data elements;
• and configured to, for each block of texture data elements:
• determine, for at least one plane that divides the block of texture data elements to be encoded into two groups in the data space, the direction of a vector in the data space from a point in the data space that is based on the values of texture data elements of the block of texture data elements to be encoded whose values lie on one side of the plane in the data space to a point in the data space that is based on the values of texture data elements of the block of texture data elements to be encoded whose values lie on the other side of the plane in the data space;
• use the direction determined in the data space of the texture data elements for at least one of the at least one planes that divide the block of texture data elements into two groups in the data space to determine a direction in the data space to be used when determining a base data value or values to be used for the block of texture data elements when encoding the block of texture data elements;
• use the at least one determined direction in the data space for the block of texture data elements to derive at least one base data value to be used when encoding the block of texture data elements;
• and
• encode the block of texture data elements as a block of texture data representing the block of texture data elements using the derived at least one base data value.

A computer readable storage medium storing computer software code which when executing on a processor performs a method of determining for a set of texture data elements to be encoded for use in a graphics processing system, a direction in the data space of the texture data elements to be used when determining a base data value or values to be used for the set of texture data elements when encoding the set of texture data elements, the method comprising:

• determining, for at least one plane that divides the set of texture data elements to be encoded into two groups in the data space, the direction of a vector in the data space from a point in the data space that is based on the values of texture data elements of the set of texture data elements to be encoded whose values lie on one side of the plane in the data space to a point in the data space that is based on the values of texture data elements of the set of texture data elements to be encoded whose values lie on the other side of the plane in the data space;
• and
• using the direction determined in the data space of the texture data elements for at least one of the at least one planes that divide the set of texture data elements into two groups in the data space to determine a direction in the data space to be used when determining a base data value or values to be used for the set of texture data elements when encoding the set of texture data elements.