US 12,087,020 B2
Image compression method and apparatus
Matteo Naccari, London (GB); and Scott Liam Ransom, Cambridge (GB)
Assigned to Synaptics Incorporated, San Jose, CA (US)
Filed by Synaptics Incorporated, San Jose, CA (US)
Filed on Sep. 15, 2021, as Appl. No. 17/475,853.
Prior Publication US 2023/0078190 A1, Mar. 16, 2023
Int. Cl. G06T 9/00 (2006.01); H04N 19/126 (2014.01); H04N 19/146 (2014.01); H04N 19/172 (2014.01); H04N 19/184 (2014.01)
CPC G06T 9/00 (2013.01) [H04N 19/126 (2014.11); H04N 19/146 (2014.11); H04N 19/172 (2014.11); H04N 19/184 (2014.11)] 12 Claims
OG exemplary drawing
 
1. A method of controlling compression of image data, the method comprising, by a quality controller:
obtaining a desired target number of bits to be generated from compression of a current image area using a predetermined compression protocol;
determining a calculated quantisation level based on the desired target number of bits using a predetermined relationship between a number of bits to be generated from compression and a quantisation level; and
selecting a discrete quantisation level from a plurality of predetermined discrete quantisation levels based on the calculated quantisation level;
determining a predicted number of bits that would result from compression of the current image area at the selected discrete quantisation level using the predetermined relationship between the number of bits to be generated from compression and the quantisation level;
determining whether the predicted number of bits exceeds the desired target number of bits; and
in response to the predicted number of bits not exceeding the desired target number of bits, providing to an encoder information to enable the encoder to determine a set of compression parameters associated with the selected discrete quantisation level;
wherein determining the calculated quantisation level based on the desired target number of bits using the predetermined relationship between the number of bits to be generated from compression and the quantisation level comprises:
computing a Lagrange multiplier λ from λ=α·β·2β·R, where R is the desired target number of bits, and α and β are variables depending on the predetermined compression protocol and the image data to be compressed; and
computing the calculated quantisation level Δ from Δ=α·λb+c, where λ is the Lagrange multiplier, and a, b and c are experimental values determined for the predetermined compression protocol.