Adaptive generation of Q-table2 for improved image quality

A method of compressing image data including steps of

• capturing image data to derive captured image data,
• statistically measuring said captured image data to develop an image data metric,
• quantizing and encoding said captured image data to derive encoded and compressed image data, and
• substituting a quantization table in accordance with said image data metric or data representing said image data metric into said encoded and compressed image data,
• wherein said step of substituting a quantization table includes a further step of
• computing or selecting a quantization table having values which increase brightness values approximately proportionally relative to a desired maximum brightness and captured image data of maximum brightness.

A method of compressing image data including steps of

• capturing image data to derive captured image data,
• statistically measuring said captured image data to develop an image data metric,
• quantizing and encoding said captured image data to derive encoded and compressed image data, substituting a quantization table in accordance with said image data metric or data representing said image data metric into said encoded and compressed image data, and
• compressing dynamic range of said captured image data prior to said step of quantizing and encoding,
• wherein said step of substituting a quantization table includes further step of
• computing or selecting a quantization table having values which approximate a product of values which increase brightness values approximately proportionally relative to a desired maximum brightness and captured image data of maximum brightness and values which approximately compensate for said step of compressing dynamic range.

A method of compressing image data including steps of

• capturing image data to derive captured image data,
• statistically measuring said captured image data to develop an image data metric,
• quantizing and encoding said captured image data to derive encoded and compressed image data, and
• substituting a quantization table in accordance with said image data metric or data representing said image data metric into said encoded and compressed image data,
• wherein said step of substituting a quantization table includes further steps of
• determining darkening of an image represented in said captured image data, and
• providing a compensating offset in orthogonal transform coefficients.

Apparatus for compressing image data including

• a sensor for capturing image data to derive captured image data,
• a data processor for statistically measuring said captured image data to develop an image data metric, quantizing and encoding said captured image data to derive encoded and compressed image data, and substituting a quantization table in accordance with said image data metric or data representing said image data metric into said encoded and compressed image data, and
• means for storing or transmitting said encoded and compressed image data including at least one of said quantization table and said data representing said metric,
• means for compressing dynamic range of said captured image data prior to said step of quantizing and encoding, and
• means for decoding and displaying said encoded and compressed image data in accordance with said quantization table substituted into said encoded and compressed image data or a quantization table derived from said metric.