Image-dependent exposure enhancement

Claim 3

The method as defined in claim 1, wherein each original color density signal, is defined in terms of red-green blue color space.

Claim 4

The method as defined in claim 2, wherein color density signals defined in terms of red-green-blue color space are converted to luminance-chrominance space, and the signal describing intensity of the image is the luminance signal.

Claim 5

The method as defined in claim 1, including the initial step of sampling the electronically encoded signals at a resolution less than the resolution of the thereof.

Claim 6

The method as defined in claim 1, wherein prior to adjusting the tone reproduction characteristics of a destination reproduction device by the exponential function γ, the value of γ is checked for validity, and if γ is an invalid value, a closest valid value of γ is substitute therefore.

Claim 7

The method as defined in claim 1, wherein the step of evaluating the function ##EQU7## using the value of I light , I dark as an address to an addressable memory to retrieve a stored value of γ.

Claim 8

An image processing system for preparing a color image for printing, and including an exposure adjustment system altering the exposure in the reproduction of an electronically encoded natural scene image, comprising: a) a memory receiving and storing an electronically encoded natural scene image, where the encoding is in terms of color density signals; b) a color space conversion circuit, converting the color density signals to an image intensity signal format, wherein at least one signal represents image intensity I and is defined for L levels of intensity; c) a thresholding circuit, receiving as inputs a pair of preset threshold signals T light , T dark , and the intensity signals, and providing at least a multi state output signal respectively indicating satisfactory brightness and darkness of the image; d) a logic controller, responsive to the state signal, and controlling transfer of the electronically encoded natural scene image directly to a subsequent image processing element if the signal state indicates that the intensity signal has dark or light values exceeding both threshold signals T light , T dark or neither threshold signals T light , T dark and responsive to a signal state indicating that the signal state indicates that the intensity signals has light or dark values exceeding one of threshold signals T light , T dark generating an evaluation signal; e) a γ calculating circuit evaluating: ##EQU8## f) means for adjusting the tone reproduction characteristics of a destination reproduction device by the exponential function γ.

Claim 9

An image processing system for preparing a color image for printing, and including an exposure adjustment system altering the exposure in the reproduction of an electronically encoded natural scene image, comprising: a) a memory receiving and storing an electronically encoded natural scene image, where the encoding is in terms of color density signals; b) a color space conversion circuit, converting the color density signals to an image intensity signal format, wherein at least one signal represents image intensity I and is defined for L levels of intensity; c) a thresholding circuit, receiving as inputs a pair of preset threshold signals T light , T dark , and the intensity signals, and providing at least a multi state output signal respectively indicating satisfactory brightness and darkness of the image; d) a logic controller, responsive to the state signal, and controlling transfer of the electronically encoded natural scene image directly to a subsequent image processing element if the signal state indicates that the intensity signal has dark or light values exceeding both threshold signals T light , T dark or neither threshold signals T light , T dark and responsive to a signal state indicating that the signal state indicates that the intensity signals has light or dark values exceeding one of threshold signals T light , T dark generating an evaluation signal; e) a γ calculating circuit evaluating: ##EQU8## f) means for adjusting the tone reproduction characteristics of a destination reproduction device by the exponential function γ.

Claim 10

The system as defined in claim 7, wherein each original electronic signal is defined in terms of red-green blue color space.

Claim 11

The system as defined in claim 8, wherein each original electronic signal is defined in terms of red-green-blue color space is converted to luminance-chrominance space, and the signal describing intensity of the image is the luminance signal.

Claim 12

The system as defined in claim 7, including the undersampling of the color density signals.

Claim 13

The system as defined in claim 7, and further comprising: a comparator having as an input the value of γ, and range of valid values for γ and generating an invalid signal when γ is outside the valid value range; and a device validity memory, storing substitute values, and returning to the tone reproduction characteristic adjusting means a substitute value of γ upon receiving an invalid signal.

Claim 14

The system as defined in claim 7 wherein the γ evaluating circuit includes a device memory, operative in response to the evaluation signals, and receiving as an address the dark or light intensity values and returning from the address location in memory a stored value of γ.

Claim 17

The method as defined in claim 13, wherein prior to adjusting the tone reproduction characteristics of a destination reproduction device by the exponential function γ, the value of γ is checked for validity, and if γ is an invalid value, a closest valid value is substitute therefor.

Claim 18

The method as defined in claim 13, including the initial step of sampling the electronically encoded intensity signals at a resolution less than the resolution thereof.

Claim 19

An image processing system for preparing a color image for printing, and including an exposure adjustment system altering the exposure in the reproduction of an electronically encoded natural scene image, comprising: a) a page buffer memory receiving and storing an electronically encoded natural scene image, where the encoding is in terms of red-green-blue color density signals; b) a color space conversion circuit, converting the color density signals to a luminance-chrominance signal format, wherein at least one signal represents image intensity I; c) a thresholding circuit, receiving as inputs a pair of preset threshold signals T light , T dark , and the intensity signals I, and providing a four state output signal respectively indicating satisfactory brightness and darkness of the image; d) a logic controller, responsive to the four state signal, and controlling transfer of the electronically encoded natural scene image directly to a subsequent image processing element if the signal state indicates that the intensity signal has dark or light values exceeding both threshold signals T light , T dark or neither threshold signals T light , T dark and responsive to a signal state indicating the intensity signal I has dark or light values exceeding one of threshold signals T light , T dark generating an evaluation signal; e) a device memory, operative in response to the evaluation signals, and receiving as an address the dark or light intensity values and returning from the address location in memory a stored value of γ for the predetermined function of ##EQU10## f) tone reproduction correction generator adapted for communication with a destination reproduction device to vary the toner reproduction response thereof by the exponential curve defined by the retrieved value γ.

Claim 20

An image processing system for preparing a color image for printing, and including an exposure adjustment system altering the exposure in the reproduction of an electronically encoded natural scene image, comprising: a) a page buffer memory receiving and storing an electronically encoded natural scene image, where the encoding is in terms of red-green-blue color density signals; b) a color space conversion circuit, converting the color density signals to a luminance-chrominance signal format, wherein at least one signal represents image intensity I; c) a thresholding circuit, receiving as inputs a pair of preset threshold signals T light , T dark , and the intensity signals I, and providing a four state output signal respectively indicating satisfactory brightness and darkness of the image; d) a logic controller, responsive to the four state signal, and controlling transfer of the electronically encoded natural scene image directly to a subsequent image processing element if the signal state indicates that the intensity signal has dark or light values exceeding both threshold signals T light , T dark or neither threshold signals T light , T dark and responsive to a signal state indicating the intensity signal I has dark or light values exceeding one of threshold signals T light , T dark generating an evaluation signal; e) a device memory, operative in response to the evaluation signals, and receiving as an address the dark or light intensity values and returning from the address location in memory a stored value of γ for the predetermined function of ##EQU10## f) tone reproduction correction generator adapted for communication with a destination reproduction device to vary the toner reproduction response thereof by the exponential curve defined by the retrieved value γ.

Claim 21

The system as defined in claim 16, and further comprising: a comparator having as an input the value of γ, and range of valid values for γ and generating an invalid signal when γ is outside the valid value range; and a device validity memory, storing substitute values, and returning to the toner reproduction characteristic adjusting means a substitute value of γ upon receiving an invalid signal.

Claim 22

The method as defined in claim 16, including the initial step of sampling the electronic signals at a resolution less than the resolution of the electronic signals.

Claim 25

The method as defined in claim 19, wherein prior to adjusting the tone reproduction characteristics of a destination reproduction device by the exponential function γ ave , the value of γ is checked for validity, and if γ is an invalid value, γ ave is set equal to γ'.

Claim 26

The method as defined in claim 19, wherein prior to adjusting the tone reproduction characteristics of a destination reproduction device by the exponential function γ ave , the value of γ' is checked for validity, and if γ' is an invalid value, γ ave is set equal to γ.

Claim 27

The method as defined in claim 19, wherein prior to adjusting the tone reproduction characteristics of a destination reproduction device by the exponential function γ ave , the value of γ' and γ is checked for validity, and if γ'nd γ are invalid value, γ ave is set equal to a closest valid value of γ.

Claim 28

The method as defined in claim 19, including the initial step of sampling the electronically encoded intensity signals at a resolution less than the resolution thereof.

Claim 29

The method as defined in claim 19, wherein the electronically encoded natural scene image is received at a page buffer memory.

Claim 30

An image processing system for preparing a color image for printing, and including an exposure adjustment system altering the exposure in the reproduction of an electronically encoded natural scene image, comprising: a) a system input receiving an electronically encoded natural scene image, where the encoding is in terms of red-green-blue color density signals; b) a color space conversion circuit, converting the color density signals to an L level luminance-chrominance signal format, wherein at least one signal represents image intensity I; c) a thresholding circuit, receiving as inputs a pair of preset threshold signals T light , T dark , and the intensity signals I, and providing a four state output signal respectively indicating satisfactory brightness and darkness of the image; d) a logic controller, responsive to the four state signal, and controlling transfer of the electronically encoded natural scene image directly to a subsequent image processing element if the signal state indicates that the intensity signal has dark or light values exceeding both threshold signals T dark , T light or neither threshold signals T dark , T light and responsive to a signal state indicating that the signal state indicates that the intensity signals has dark or light values exceeding one of threshold signals T dark , T light generating an evaluation signal; e) a γ calculating circuit evaluating: ##EQU12## f) a thresholding circuit, receiving as inputs a pair of preset threshold signals T light , T dark , and the intensity signals, subtracting those portions of the intensity signal in preselected outer bands of intensity, and providing a four state output signal respectively indicating satisfactory brightness and darkness of the image; g) a logic controller, responsive to the four state signal, and controlling transfer of the electronically encoded natural scene image directly to a subsequent image processing element if the signal state indicates that the intensity signal has dark or light values exceeding both threshold signals T' dark , T' light or neither threshold signals T' dark , T' light and responsive to a signal state indicating that the signal state indicates that the intensity signals has dark or light values exceeding one of threshold signals T' dark , T' light generating an evaluation signal; h) a γ' calculating circuit evaluating: ##EQU13## i) an averaging circuit for averaging γ' and γ to obtain γ ave ; j) a destination reproduction device having a tone reproduction relating input signals to output response thereof, and responsive to the averaging circuit to vary the output response by the exponential function γ ave .

Claim 31

An image processing system for preparing a color image for printing, and including an exposure adjustment system altering the exposure in the reproduction of an electronically encoded natural scene image, comprising: a) a system input receiving an electronically encoded natural scene image, where the encoding is in terms of red-green-blue color density signals; b) a color space conversion circuit, converting the color density signals to an L level luminance-chrominance signal format, wherein at least one signal represents image intensity I; c) a thresholding circuit, receiving as inputs a pair of preset threshold signals T light , T dark , and the intensity signals I, and providing a four state output signal respectively indicating satisfactory brightness and darkness of the image; d) a logic controller, responsive to the four state signal, and controlling transfer of the electronically encoded natural scene image directly to a subsequent image processing element if the signal state indicates that the intensity signal has dark or light values exceeding both threshold signals T dark , T light or neither threshold signals T dark , T light and responsive to a signal state indicating that the signal state indicates that the intensity signals has dark or light values exceeding one of threshold signals T dark , T light generating an evaluation signal; e) a γ calculating circuit evaluating: ##EQU12## f) a thresholding circuit, receiving as inputs a pair of preset threshold signals T light , T dark , and the intensity signals, subtracting those portions of the intensity signal in preselected outer bands of intensity, and providing a four state output signal respectively indicating satisfactory brightness and darkness of the image; g) a logic controller, responsive to the four state signal, and controlling transfer of the electronically encoded natural scene image directly to a subsequent image processing element if the signal state indicates that the intensity signal has dark or light values exceeding both threshold signals T' dark , T' light or neither threshold signals T' dark , T' light and responsive to a signal state indicating that the signal state indicates that the intensity signals has dark or light values exceeding one of threshold signals T' dark , T' light generating an evaluation signal; h) a γ' calculating circuit evaluating: ##EQU13## i) an averaging circuit for averaging γ' and γ to obtain γ ave ; j) a destination reproduction device having a tone reproduction relating input signals to output response thereof, and responsive to the averaging circuit to vary the output response by the exponential function γ ave .

Claim 32

The system as defined in claim 25, and further comprising: a comparator having as an input the value of γ, and range of valid values for γ and generating an invalid signal when γ is outside the valid value range; and a device validity memory, storing substitute values, and returning to the toner reproduction characteristic adjusting means a substitute value of γ upon receiving an invalid signal.

Claim 33

A color reproduction system acquiring and printing a color image, and including an exposure adjustment circuit altering the exposure in the reproduction of an natural scene image, comprising: a) a scanner suitable for generating a digitally encoded natural scene image from an original scene, in terms of color density signals; b) a multicolor printer, responsive to signals directed thereto to print an image, and provided with a tone reproduction control relating input signals to printer response; c) a color space conversion circuit, converting the color density signals to an L level luminance-chrominance signal format, wherein at least one signal represents image intensity I; d) an exposure adjustment circuit including i) a thresholding circuit, receiving as inputs a pair of preset threshold signals T light , T dark , and the intensity signals I, and providing a multi state output signal respectively indicating satisfactory brightness and darkness of the image; ii) a logic controller, responsive to the multi state signal, and controlling transfer of the electronically encoded natural scene image directly to a subsequent image processing element if the signal state indicates that the intensity signal has dark or light values exceeding both of threshold signals T light , T dark , or neither of threshold signals T light , T dark , and responsive to a signal state indicating that the intensity signals has dark or light values exceeding one of threshold signals T light , T dark , to generate an evaluation signal; iii) a γ calculating circuit, responsive to the evaluation signals to evaluate the function: ##EQU14## e) said toner reproduction control responsive to said calculated γ to correct the printer response to the a digitally encoded natural scene image as an exponential function of γ.

Claim 34

A color reproduction system acquiring and printing a color image, and including an exposure adjustment circuit altering the exposure in the reproduction of an natural scene image, comprising: a) a scanner suitable for generating a digitally encoded natural scene image from an original scene, in terms of color density signals; b) a multicolor printer, responsive to signals directed thereto to print an image, and provided with a tone reproduction control relating input signals to printer response; c) a color space conversion circuit, converting the color density signals to an L level luminance-chrominance signal format, wherein at least one signal represents image intensity I; d) an exposure adjustment circuit including i) a thresholding circuit, receiving as inputs a pair of preset threshold signals T light , T dark , and the intensity signals I, and providing a multi state output signal respectively indicating satisfactory brightness and darkness of the image; ii) a logic controller, responsive to the multi state signal, and controlling transfer of the electronically encoded natural scene image directly to a subsequent image processing element if the signal state indicates that the intensity signal has dark or light values exceeding both of threshold signals T light , T dark , or neither of threshold signals T light , T dark , and responsive to a signal state indicating that the intensity signals has dark or light values exceeding one of threshold signals T light , T dark , to generate an evaluation signal; iii) a γ calculating circuit, responsive to the evaluation signals to evaluate the function: ##EQU14## e) said toner reproduction control responsive to said calculated γ to correct the printer response to the a digitally encoded natural scene image as an exponential function of γ.