Method and apparatus for compressing images

• US 5,892,847 A
• Filed: 04/22/1996
• Issued: 04/06/1999
• Est. Priority Date: 07/14/1994
• Status: Expired due to Term

• Current Assignee: Citrix Systems, Inc. (Cloud Software Group)
• Original Assignee: Johnson-Grace (Warner Bros. Discovery, Inc.)
• Inventors: Johnson, Stephen G.
• Primary Examiner(s): Couso, Jose L.
• Assistant Examiner(s): Bella, Matthew C.
• Application Number:
  US08/636,170
• Time in Patent Office: 1,079 Days
• Field of Search: 382/166, 382/232, 382/233, 382/235, 382/236, 382/239, 382/304, 382/303, 348/497, 348/398, 348/403, 348/422, 348/416, 358/261.2, 358/426, 358/430
• US Class Current: 382/232
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/186 the unit being a colour or a chrominance component
• CPC Class Codes: H04N 19/30 using hierarchical techniques, e.g. scalability H04N19/63 takes precedence
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets
• CPC Class Codes: H04N 19/80 Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation H04N19/635, H04N19/86 take precedence
• CPC Class Codes: H04N 19/94 Vector quantisation

Abstract

A system and method is disclosed that compresses and decompresses images. The compression system and method includes an encoder which compresses images and stores such compressed images in a unique file format, and a decoder which decompresses images. The encoder optimizes the encoding process to accommodate different image types with fuzzy logic methods that automatically analyze and decompose a source image, classify its components, select the optimal compression method for each component, and determine the optimal parameters of the selected compression methods. The encoding methods include: a Reed Spline Filter, a discrete cosine transform, a differential pulse code modulator, an enhancement analyzer, an adaptive vector quantizer and a channel encoder to generate a plurality of data segments that contain the compressed image. The plurality of data segments are layered in the compressed file to optimize the decoding process. The first layer allows the decoder to display the compressed image as a miniature or a coarse quality full sized image, the decoder then adds additional detail and sharpness to the displayed image as each new layer is received. The decoder uses optimal decompression methods to expand the compressed image file.

Claims

1. Image encoding system, comprising:

a first element, operating to receive a source image and to format the source image in a way to allow its coding;

a first compression coder, which filters the formatted source image, to form a first compressed and coarse quality image having less resolution then said source image;

an image classifier, operating on said first compressed image to classify the information contained in the image according to a characteristic thereof that is related to an amount by which the image can be compressed;

a compression encoder, determining one of a plurality of compression methods that will optimize the amount of compression based on a result of said image classifier, and encoding said information using the optimized compression method to produce a second compressed image that contains information about the image that is to be added to said first compressed image;

a message assembling element interleaving information indicative of the first image and the second image into a desired form in message transmitting format, and transmitting said message to a channel.

2. A system as in claim 1, wherein said first element includes a decimating stage forming a miniature image, and said compression encoder uses a different kind of compression than said decimating.

3. An image decoder system, comprising:

a first element, connected to a transmission channel to receive transmitted, compressed data indicative of an image therefrom, said compressed data received in layers;

a display interface which receives information to be displayed;

a first layer detector and decompression element, detecting a complete first layer, and decompressing said first layer when complete, to produce first information indicative of a reduced quality image, based on said first layer after decoding said first layer using a decompression technique and sending said first information to said display interface; and

a second layer detector and decompression element, receiving a second layer of image information, compressed using a different compression technique than said first layer, and detecting that at least a unit of said second layer has been completely received, and decompressing said second layer to produce additional information which is coupled to said display interface to improve a displayed image resolution.

4. A system as in claim 3, further comprising a third layer detector, receiving and decompressing a third layer of information, forming a final display.

5. A system as in claim 4, wherein said units of said second layer are display panels, each panel displayed when completed, to form the second layer of the image in panels.

6. A system as in claim 3, further comprising an image classifying module, that determines a characteristic of the image indicative of a best technique of compression, to output a measure indicative of said best technique.

7. A system as in claim 6, wherein said image classifying module uses fuzzy logic techniques.

8. A system as in claim 6, wherein said image types include gray scale, graphics, text, photographs, high activity and low activity images.

9. A method of encoding a source image, comprising:

obtaining a first compressed version of the image, said first compressed version of the image corresponding to a coarse version of the image indicative of coarse details only, said first compressed version of the image obtained using a first compression technique;

analyzing said coarse version of the image to determine which of a plurality of different compression techniques will best further compress said image; and

further compressing said image to obtain further information indicative of a better rendering of said image beyond that provided by said coarse version, than said coarse version of said image, using the compression technique determined by said analyzing;

using both said coarse version of said image and said further information to represent the compressed image; and

obtaining a reconstructed coarse image from the discrete cosine transform coefficients, determining a residual between the reconstructed image and the coarse image and compressing the residual.

10. An image encoding device, comprising:

a first stage, operating to produce first information indicating a reduced quality compressed version of the original image;

a second stage which analyzes the first information to determine an image classification thereof, and outputs a control script indicative of an efficient compression method based on said image classification;

a third stage, responsive to said control script, to select a compression method from among a plurality of compression methods based on said control script and compressing image information using said compression method to produce second information; and

a fourth stage which assembles the first information and the second information into a message to be sent;

wherein said first stage comprises a component separator, separating chrominance components from luminance components;

wherein said first stage decimates said chrominance components; and

said third stage compresses said luminance components using a discrete cosine transform technique.

11. A device as in claim 10, wherein said second stage comprises a discrete cosine transform coefficient determining device, determining optimal quantization step sizes, and quantitizing discrete cosine transform coefficients using said optimal step sizes.

12. An image encoding device, comprising:

a first stage, operating to produce first information indicating a reduced quality compressed version of the original image;

a second stage which analyzes the first information to determine an image classification thereof, and outputs a control script indicative of an efficient compression method based on said image classification;

a third stage, responsive to said control script, to select a compression method from among a plurality of compression methods based on said control script and compressing image information using said compression method to produce second information; and

a fourth stage which assembles the first information and the second information into a message to be sent;

wherein said first stage comprises a component separator, separating chrominance components from luminance components;

wherein said first stage decimates said chrominance components; and

said third stage compresses said luminance components using a discrete cosine transform technique;

wherein said second stage comprises a discrete cosine transform coefficient determining device, determining optimal quantization step sizes, and quantitizing discrete cosine transform coefficients using said optimal step sizes.

13. A device as in claim 12 wherein said fifth stage comprises an adaptive vector quantitizer operating to compress the residual by matching the residual against a group of commonly-occurring block patterns in a codebook.

14. An image encoding device, comprising:

a first stage, operating to produce first information indicating a reduced quality compressed version of the original image;

a second stage which analyzes the first information to determine an image classification thereof, and outputs a control script indicative of an efficient compression method based on said image classification;

a third stage, responsive to said control script, to select a compression method from among a plurality of compression methods based on said control script and compressing image information using said compression method to produce second information;

a fourth stage which assembles the first information and the second information into a message to be sent;

wherein said second stage comprises a discrete cosine transform coefficient determining device, determining optimal quantization step sizes, and quantitizing discrete cosine transform coefficients using said optimal step sizes;

wherein said chrominance is compressed by decimating the color, and fitting the decimated data to a spline function to determine optimal reconstruction weights to minimize a mean squared error.

15. A method of selectively coding an image, comprising:

dividing said image into a plurality of areas, each area representing a portion of the image;

comparing each said area with a value indicating whether said area should or should not be rendered in an enhanced mode;

adding a prioritized value to an enhancement list for each of said areas that will be rendered in the enhanced mode;

compressing values which are on said enhancement list using a high resolution compression technique;

compressing values which are not on said enhancement list using a different compression technique; and

wherein said high resolution compression technique is a high resolution residual calculator.