Lossless compressor for image data values

A method of encoding a set of data values, each said data value corresponding to a pixel position within an image, said method comprising, for a current said data value at a current pixel position, the steps of:

• (a) creating a context set comprising a plurality of previously encoded data values;
• (b) computing a difference value using said current data value and each said data value in said context set;
• and
• (c) encoding said current data value by encoding the least positive said computed difference value.

A method of decoding an encoded set of data values, each said data value corresponding to a pixel position within an image, said method comprising, for a current said encoded data value at a current pixel position, the steps of:

• (a) creating a context set comprising a plurality of previously decoded data values;
• (b) computing possible values using a difference value and said decoded data values in said context set;
• and
• (c) decoding said encoded data value by selecting one of the computed possible values.

A computer readable medium having a computer program recorded thereon, the program being executable by a computer device to encode a set of data values, each said data value corresponding to a pixel position for representing an image, said program comprising:

• code for processing a current said data value at a current pixel position, said code for processing including:
• (a) code for creating a context set for said data value, said context set including a data value at a pixel position in said set immediately preceding said current pixel position in an encoding order, wherein said immediately preceding pixel position is not adjacent said current pixel position within said image;
• and
• (b) code for encoding said data value using said created context set.

A computer readable medium having a computer program recorded thereon, the program being executable by a computer device to encode a set of data values, each said data value corresponding to a pixel position within an image, said program comprising:

• code for processing a current said data value at a current pixel position, said code for processing including:
• (a) code for creating a context set comprising a plurality of previously encoded data values;
• (b) code for computing a difference value using said current data value and each said data value in said context set;
• and
• (c) code for encoding said current data value by encoding the least positive said computed difference value.

A computer readable medium having a computer program recorded thereon, the program being executable by a computer device to decode an encoded set of data values, each said data value corresponding to a pixel position within an image, said program comprising, for:

• code for processing a current said encoded data value at a current pixel position, said code for processing comprising:
• (a) code for creating a context set comprising a plurality of previously decoded data values;
• (b) code for computing possible values using a difference value and said decoded data values in said context set;
• and
• (c) code for decoding said encoded data value by selecting one of the computed possible values.