Image compression and decompression using block prediction

A method performed by a computer system for decoding a compressed digital image, the method comprising:

• identifying, in the image, a target block to be decoded;
• identifying, in the image, a set of candidate source blocks for predicting the target block;
• ranking the candidate source blocks in an order;
• retrieving, from the image, a position of a candidate source block in the ranked order, wherein the candidate source block is a reference block, and wherein the reference block was selected during compression of the digital image responsive to a size of residual information indicating how well the reference block predicts the target block and a size of information used to specify the position;
• decoding the target block using the reference block;
• and
• storing an uncompressed image having the decoded target block.

A computer-implemented system for compressing a digital image, the system comprising:

• a computer processor;
• and
• a non-transitory computer-readable storage medium storing computer program modules configured to execute on the computer processor, the computer program modules comprising:
• a target block selector module configured to:
• identify, in an image, a target block to be encoded;
• a reference block selector module configured to:
• identify, in the image, candidate source blocks for predicting the target block;
• rank the candidate source blocks in an order;
• select a reference block from among the candidate source blocks, the reference block identified by a position in the ranked order and selected responsive to a size of residual information indicating how well the reference block predicts the target block and a size of information used to specify the position;
• a block encoder module configured to:
• encode the target block using the reference block;
• and store a compressed image having the encoded target block.

A computer program product having a non-transitory computer-readable storage medium storing computer-executable code for compressing a digital image, the code comprising:

• a target block selector module configured to:
• identify, in an image, a target block to be encoded;
• a reference block selector module configured to:
• identify, in the image, candidate source blocks for predicting the target block;
• rank the candidate source blocks in an order;
• select a reference block from among the candidate source blocks, the reference block identified by a position in the ranked order and selected responsive to a size of residual information indicating how well the reference block predicts the target block and a size of information used to specify the position;
• a block encoder module configured to:
• encode the target block using the reference block;
• and
• store a compressed image having the encoded target block.