Patent ID: 11915455
Assignee: IMAGINATION TECHNOLOGIES LIMITED
Field: Audio-visual technology (Electrical engineering)
Classification: CPC G  H | IPC G

Claim 17:
18. A compression unit to compress a block of image data, the block of image data comprising a plurality of image element values, each image element value being formed of at least a first value such that the block of image data comprises a two- dimensional block of first values, the two-dimensional block of first values being divided into at least one size of sub-blocks of first values, the compression unit comprising:
a header generation unit configured to:
dynamically select which of the two-dimensional block of first values and the sub- blocks of first values are to be stored in compressed format, and
form a header of a compressed block for the block of image data comprising:
information for the two-dimensional block of first values indicating whether the two-dimensional block of first values is in compressed format,
information for each sub-block of first values indicating whether that sub- block of first values is in compressed format, and
for each block and sub-block of first values that is in compressed format, common base information that is common to the first values of that block or sub-block; and

a body generation unit configured to form a body for the compressed block that comprises:
for each first value that forms part of a block or sub-block of first values that is in compressed format, a fixed-length parameter for that first value that is zero, one or more than one bits in length, that first value being obtainable from the common base information for that block or sub-block and the fixed-length parameter for that first value, and
for each first value that does not form part of a block or sub-block of first values that is in compressed format, that first value.