Compression processing apparatus and compression processing method
View Patent ↗A dividing unit divides respective symbol sequences of input data applied with zigzag scan and a run-length process into a plurality of subsets having similar frequencies of occurrence, depending on a difference in frequencies of occurrence. A table creating unit scans each subset and creates a Huffman coding table for each subset. A coding unit executes a process for performing Huffman coding on each subset by using the Huffman coding table created for the subset, for all of the subsets in the plurality of subsets.
1. A compression processing apparatus compressing input data and outputting compressed data, comprising:
a dividing unit dividing a plurality of elements included in a population having said input data into a plurality of subsets by using a feature of each element;
a coding unit performing Huffman coding on coding target data for each subset by using a plurality of Huffman coding tables provided corresponding to said plurality of subsets, and outputting said compressed data;
a table retaining unit retaining first and second coding tables each having a plurality of Huffman codes; and
an updating unit updating one coding table which is not used for the Huffman coding on said input data, in said first and second coding tables, depending on a frequency of occurrence of said coding target data so that the coding target data with a highest frequency of occurrence is converted into a shortest Huffman code,
wherein when a compression ratio of said compressed data is equal to or less than a threshold, said coding unit performs the Huffman coding on said coding target data for said each subset while creating said plurality of Huffman coding tables, based on the other coding table in said first and second coding tables, and when said compression ratio becomes larger than said threshold, said coding unit performs the Huffman coding on said coding target data for said each subset while creating said plurality of Huffman coding tables, based on the one coding table updated by said updating unit.
2. The compression processing apparatus according to claim 1 , further comprising a table creating unit creating said plurality of Huffman coding tables by executing, for all of said plurality of subsets, a process for examining a frequency of occurrence of the coding target data included in one subset and creating the Huffman coding table corresponding to said one subset.
3. The compression processing apparatus according to claim 1 , wherein said updating unit counts the frequency of occurrence for all of the coding target data, updates said one coding table by executing a process for, each time the frequency of occurrence for one of the coding target data reaches a maximum value, assigning a new Huffman code having a shorter length to said one of the coding target data for which said frequency of occurrence has reached said maximum value earlier in order thereof, for said all of the coding target data.
4. The compression processing apparatus according to claim 3 , wherein said updating unit calculates said compression ratio based on the compressed data outputted from said coding unit, and, when the calculated compression ratio has become larger than said threshold, or when said new Huffman code has been assigned to said all of the coding target data, said updating unit generates an exchanging signal for exchanging said coding table and outputs the exchanging signal to said coding unit, and
said coding unit exchanges said coding table in response to said exchanging signal, and performs the Huffman coding on said coding target data for said each subset while creating said plurality of Huffman coding tables, based on the exchanged coding table.
5. The compression processing apparatus according to claim 1 , further comprising:
an image segmenting unit segmenting an image into a plurality of images based on target objects included in said image and generating a plurality of input data,
wherein said dividing unit executes a process dividing a plurality of elements included in a population having one of input data in said plurality of input data, into a plurality of subsets by using a feature of each element, for all of said plurality of input data, and
said coding unit executes a process performing the Huffman coding on coding target data for each subset by using a plurality of Huffman coding tables provided corresponding to the plurality of subsets divided from said one of input data, and outputting said compressed data, for all of said plurality of input data.
6. A compression processing method compressing input data and outputting compressed data, comprising:
a first step of a dividing unit dividing a plurality of elements included in a population having said input data into a plurality of subsets by using a feature of each element;
a second step of a coding unit performing Huffman coding on coding target data for each subset by using a plurality of Huffman coding tables provided corresponding to said plurality of subsets, and outputting said compressed data; and
a third step of an updating unit updating one coding table which is not used for the Huffman coding on said input data, in first and second coding tables each having a plurality of Huffman codes, depending on a frequency of occurrence of the coding target data so that the coding target data with a highest frequency of occurrence is converted into a shortest Huffman code,
wherein, in said second step, when a compression ratio of said compressed data is equal to or less than a threshold, said coding unit performs the Huffman coding on said coding target data for said each subset while creating said plurality of Huffman coding tables, based on the other coding table in said first and second coding tables, and when said compression ratio becomes larger than said threshold, said coding unit performs the Huffman coding on said coding target data for said each subset while creating said plurality of Huffman coding tables, based on said one coding table.
7. The compression processing method according to claim 6 , further comprising a fourth step of a table creating unit creating said plurality of Huffman coding tables by executing, for all of said plurality of subsets, a process examining a frequency of occurrence of the coding target data included in one subset and creating the Huffman coding table corresponding to said one subset.
8. The compression processing method according to claim 6 , wherein said third step includes:
a first substep of said updating unit counting the frequency of occurrence for all of the coding target data; and
a second substep of said updating unit updating said one coding table by executing a process for, each time the frequency of occurrence for one of the coding target data reaches a maximum value, assigning a new Huffman code having a shorter length to said one of the coding target data for which said frequency of occurrence has reached said maximum value earlier in order thereof, for said all of the coding target data.
9. The compression processing method according to claim 8 , wherein said third step further includes:
a third substep of said updating unit calculating said compression ratio based on the compressed data outputted from said coding unit; and
a fourth substep of, when the compression ratio calculated in said third substep has become larger than said threshold, or when said new Huffman code has been assigned to said all of the coding target data, said updating unit generating an exchanging signal for exchanging said coding table and outputting the exchanging signal to said coding unit, and
in said second step, said coding unit exchanges said coding table in response to said exchanging signal, and performs the Huffman coding on said coding target data for said each subset while creating said plurality of Huffman coding tables, based on the exchanged coding table.
10. The compression processing method according to claim 6 , further comprising:
a fourth step of an image segmenting unit segmenting an image into a plurality of images based on target objects included in said image and generating a plurality of input data,
wherein, in said first step, said dividing unit executes a process dividing a plurality of elements included in a population having one of input data in said plurality of input data, into a plurality of subsets by using a feature of each element, for all of said plurality of input data, and
in said second step, said coding unit executes a process performing the Huffman coding on coding target data for each subset by using a plurality of Huffman coding tables provided corresponding to the plurality of subsets divided from said one of input data, and outputting said compressed data, for all of said plurality of input data.