Hybrid wavelet and JPEG system and method for compression of color images

A method of decoding encoded YUV format image data comprising the steps of:

• accessing encoded Y, U and V data within the encoded YUV format image data;
• decoding the encoded Y data with a wavelet decompression procedure;
• determining whether the encoded U and V data was encoded using wavelet compression;
• when it is determined that wavelet compression was used to encode the U and V data, decoding the encoded U and V data with the wavelet decompression procedure, and otherwise decoding the encoded U and V data with a JPEG decompression procedure.

An apparatus for encoding digital image data comprising:

• a processor;
• a working memory;
• input circuitry for receiving digital image data and a selection signal that corresponds to a selected image quality level selection, and for storing the received digital image data in the working memory;
• and
• circuitry coupled to the working memory for encoding the image data stored in the working memory, the image data including Y, U and V data, wherein the circuitry includes wavelet compression logic for compressing data using a wavelet compression method and JPEG compression logic for compressing data using a JPEG compression method, and control logic for directing the circuitry to compress the U and V data using the JPEG compression logic when the image quality level selection is in a predefined set of one or more high quality image levels and for otherwise directing the circuitry to compress the U and V data using the wavelet compression logic.

A computer program product for use in conjunction with a computer system, the computer program product comprising a computer readable storage medium and a computer program mechanism embedded therein, the computer program mechanism comprising:

• a JPEG compression procedure for compressing image data;
• a wavelet compression procedure for compressing image data;
• and
• an image compression control procedure for controlling compression of image data that includes Y, U and V data, including:
• instructions for determining a compression ratio;
• instructions for compressing the Y data using the wavelet compression procedure;
• and
• instructions for compressing the U and V data with a JPEG compression procedure when the compression ratio is in a predefined low compression range, and otherwise compressing the U and V data with the wavelet compression procedure.

A method of encoding image data comprising the steps of:

• accessing within the image data a luminance component, Y, and a plurality of spectral components Ai, for i=1 to N, where N is a positive integer greater than 1;
• compressing the Y data using a wavelet compression procedure;
• determining a compression ratio;
• and
• when the compression ratio is in a first predefined range, compressing a first one of the spectral components A1 with a JPEG compression procedure, and otherwise compressing the A1 data with the wavelet compression procedure.

An apparatus for encoding digital image data comprising:

• a processor;
• a working memory;
• input circuitry for receiving digital image data and a selection signal that corresponds to a selected image quality level selection, and for storing the received digital image data in the working memory;
• and
• circuitry coupled to the working memory for encoding the image data stored in the working memory, the image data including luminance data, Y, and a plurality of spectral component data Ai, for i=1 to N, where N is a positive integer greater than 1;
• wherein the circuitry includes wavelet compression logic for compressing data using a wavelet compression method and JPEG compression logic for compressing data using a JPEG compression method, and control logic for directing the circuitry to compress the A1 data for a first one of the spectral components using the JPEG compression logic when the image quality level selection is in a first predefined set of one or more high quality image levels and for otherwise directing the circuitry to compress the A1 data using the wavelet compression logic.