Digital electronic still camera

• US 5,295,077 A
• Filed: 01/23/1992
• Issued: 03/15/1994
• Est. Priority Date: 01/23/1991
• Status: Expired due to Term

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Fukuoka, Hiroki
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): Lee, Fan
• Application Number:
  US07/824,225
• Time in Patent Office: 782 Days
• Field of Search: 358/467, 358/427, 358/426, 358/261.2, 358/261.1, 358/432, 358/479, 358/448, 358/296, 358/433, 358/133, 358/136, 358/135, 358/909, 358/462, 358/444, 382/56, 395/900, 364/725, 364/724.16
• US Class Current: 358/479
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: Y10S 706/90 Fuzzy logic

Abstract

A digital electronic still camera has an image pickup device to pick up an image to be photographed. The picked-up image data is compressed by a data compressing unit using the two-dimensional discrete cosine transformation (DCT), the optimum quantization table, and the Huffman coding. The optimum quantization table is selected by comparing a characteristic parameter of the image data with preliminarily obtained values for respective image kinds. The two-dimensional DCT provides transformation coefficients of image, which are linearly quantized with reference to the optimum quantization table. The quantized data is coded by the Huffman coding method to have a minimum length. The coded data is sent to a recording device, which records the coded data in a recording medium such as a memory card. Fuzzy control theory may be applied to determine whether the image attributes to a document, a portrait, or a landscape. The image attribute may also manually be set, for example, on an input device.

Claims

1. A digital electronic still camera, comprising:

image pickup means for picking up an image of a field to be photographed;

block-dividing means for dividing the image into a plurality of blocks which are respectively made up of a plurality of pixels;

transforming means for executing an adaptive discrete cosine transformation of each block of the image to generate a corresponding block of image data;

quantizing means for quantizing the image data of each block with reference to a quantization table selected as an optimum one from a plurality of quantization tables having different quantization step sizes;

image attributable judging means for judging an image attribute based on a spectrum distribution of the image data selected as membership functions of fuzzy decision;

quantization table setting means for selecting a quantization table as the optimum one based on the image attribute obtained;

coding means for coding the image data quantized; and

recording means for recording the coded image data into a memory.

2. A digital electronic still camera according to claim 1, wherein the plurality of quantization tables are quantization tables for a document, a portrait and a landscape.

3. A digital electronic still camera according to claim 2, wherein the optimum quantization table is constructed by selecting a quantization table based on the image attribute obtained and multiplying the selected quantization table by a scaling factor.

4. A digital electronic still camera according to claim 1, wherein the plurality of quantization tables are quantization tables for a document and a nature.

5. A digital electronic still camera according to claim 4, wherein the optimum quantization table is constructed by selecting a quantization table based on the image attribute obtained and multiplying the selected quantization table by a scaling factor.

6. A digital electronic still camera according to claim 1, wherein the plurality of blocks are respectively made up of N×

N pixels, where N is an integer greater than or equal to two.

7. A digital electronic still camera, comprising:

image pickup means for picking up an image of a field to be photographed;

block-dividing means for dividing the image into a plurality of blocks which are respectively made up of a plurality of pixels;

transforming means for executing an orthogonal transformation of each block of the image to generate a corresponding block of image data;

quantizing means for quantizing the image data of each block with reference to a quantization table selected as an optimum one from a plurality of quantization tables including at least a quantization table for a document;

image attribute judging means for judging an image attribute based on a spectrum distribution of the image data selected as membership functions as fuzzy decision;

quantization table setting means for selecting a quantization table as the optimum one based on the image attribute obtained;

coding means for coding the image data quantized; and

recording means for recording the coded image data into a memory card.

8. A digital electronic still camera according to claim 7, wherein the orthogonal transformation is an adaptive discrete cosine transformation.

9. A digital electronic still camera according to claim 7, wherein the plurality of blocks are respectively made up of N×

N pixels, where N is an integer greater than or equal to two.