Programmable apparatus for determining document background level

Claim 2

In an image processing system suitable for processing an image represented by a plurality of video signals, said video signals representing both the content regions of the image and the background regions of the image, an apparatus for determining the background level of the image comprising: sampling means for sampling a selected portion of the video signals in the image; means, coupled to said sampling means, for identifying sampled video signals which are non-representative of the background regions of the image, said identifying means eliminating the non-representative video signals from the selected portion of the video signals; and means, coupled to said identifying means, for calculating a background level as a function of the level of the non-eliminated sampled video signals.

Claim 3

The image processing device of claim 1 wherein the sampling means includes: windowing means for identifying a sample region within the image; and control means, responsive to said windowing means, for indicating when a video signal received by the background determination apparatus is within the sample region.

Claim 4

The image processing device of claim 1 wherein said identifying means includes: memory means for receiving and storing a background threshold; means, in communication with said memory means, for comparing the level of the sampled video signal against the stored background threshold and providing a signal indicating when the sampled video signal is below the background threshold; and means, responsive to the signal produced by said comparing means, for eliminating the non-representative video signal.

Claim 5

In an image processing system suitable for processing an image represented by a plurality of video signals, said video signals representing both the content regions of the image and the background regions of the image, an apparatus for determining the background level of the image comprising: sampling means for sampling a selected portion of the video signals in the image; means, coupled to said sampling means, for identifying sampled video signals which are non-representative of the background regions of the image, including memory means for receiving and storing a background threshold, means, in communication with said memory means, for comparing the level of the sampled video signal against the stored background threshold and providing a signal indicating when the sampled video signal is below the background threshold, means, responsive to the signal produced by said comparing means, for eliminating the non-representative video signal, said eliminating means eliminating the non-representative video signals from the selected portion of the video signals; means, coupled to said identifying means, for calculating a background level as a function of the level of the remaining sampled video signals; and means for substituting an alternate video signal for each non-representative signal eliminated.

Claim 6

In an image processing system suitable for processing an image represented by a plurality of video signals, said video signals representing both the content regions of the image and the background regions of the image, an apparatus for determining the background level of the image comprising: sampling means for sampling a selected portion of the video signals in the image; means, coupled to said sampling means, for identifying sampled video signals which are non-representative of the background regions of the image, including memory means for receiving and storing a background threshold, means, in communication with said memory means, for comparing the level of the sampled video signal against the stored background threshold and providing a signal indicating when the sampled video signal is below the background threshold, means, responsive to the signal produced by said comparing means, for eliminating the non-representative video signal, said eliminating means eliminating the non-representative video signals from the selected portion of the video signals; means, coupled to said identifying means, for calculating a background level as a function of the level of the remaining sampled video signals; and means for substituting an alternate video signal for each non-representative signal eliminated.

Claim 7

The image processing device of claim 4 wherein the calculating means includes means for calculating a weighted running average of the levels of the non-eliminated video signals with the weighted running average being updated for each video signal received, and wherein the substituting means substitutes the weighted running average for the discarded signal.

Claim 8

In an image processing system suitable for processing an image represented by a plurality of video signals, said video signals representing both the content regions of the image and the background regions of the image, an apparatus for determining the background level of the image comprising: sampling means for sampling a selected portion of the video signals in the image; means, coupled to said sampling means, for identifying sampled video signals which are non-representative of the background regions of the image, said identifying means eliminating the non-representative video signals from the selected portion of the video signals; means, coupled to said identifying means, for calculating a first background level as a function of the level of the non-eliminated sampled video signals; and means for computing a second background level for use by the image processing system, with the second background level being a fractional portion of the first background level.

Claim 9

In an image processing system suitable for processing an image represented by a plurality of video signals, said video signals representing both the content regions of the image and the background regions of the image, an apparatus for determining the background level of the image comprising: sampling means for sampling a selected portion of the video signals in the image; means, coupled to said sampling means, for identifying sampled video signals which are non-representative of the background regions of the image, said identifying means eliminating the non-representative video signals from the selected portion of the video signals; means, coupled to said identifying means, for calculating a first background level as a function of the level of the non-eliminated sampled video signals; and means for computing a second background level for use by the image processing system, with the second background level being a fractional portion of the first background level.

Claim 10

The image processing device of claim 6 including means, responsive to the second background level, for delimiting at least two distinct ranges of signal levels to be used for classification of video signals having levels falling within the ranges.

Claim 11

The image processing device of claim 6 wherein said computing means comprises: means for storing at least one binary fraction; and a serial multiplier suitable for determining the product of the stored binary fraction and the background level.

Claim 12

The image processing device of claim 6 wherein the computing means comprises: first storing means for storing at least one digital fraction; and a serial multiplier, coupled to said first storing means, for sequentially multiplying the stored digital fraction by the first background level to produce the second background level.

Claim 13

The image processing device of claim 9 wherein the computing means further comprises: second storing means for storing at least one additional background level produced by the serial multiplier; and logic control means for controlling the selection of the first storing means and the second storing means in conjunction with the sequencing of the serial multiplier, so as to enable the computation of at least two additional background levels.

Claim 14

The image processing device of claim 6 wherein said calculating means includes averaging means for determining an average of the levels of all the non-eliminated video signals.

Claim 15

The image processing device of claim 11 wherein said averaging means determines a weighted running average of the signals, with the weighted running average being updated for each video signal received.

Claim 20

The apparatus of claim 14 further including means for computing at least one additional background magnitude with the additional background magnitude being a function of the background magnitude.

Claim 21

The apparatus of claim 14 wherein the windowing means is programmable, thereby allowing the portion of the video signals in the image which are selected to be included in the determination of the background magnitude to be established by an external data source.

Claim 22

The apparatus of claim 14 wherein the arithmetic means includes means for calculating an average of the magnitudes of the non-eliminated video signals.

Claim 23

The apparatus of claim 17 wherein said average calculating means determines a weighted running average of the signal magnitudes with the weighted running average being updated for each selected video signal received.

Claim 24

The apparatus of claim 14 wherein the eliminating means includes: memory means for receiving and storing a background threshold value; means, in communication with said memory means, for comparing the magnitude of the video signal against the stored background threshold value and producing a control signal whenever the magnitude of the video signal is less than the background threshold value, thereby identifying the video signal as a content region video signal; and means, responsive to the control signal, for bypassing the content region video signal at any time the comparing means produces the control signal.

Claim 25

The apparatus of claim 19, further including means for substituting an alternate video signal for each content region video signal bypassed.

Claim 26

The apparatus of claim 19 wherein said eliminating means is programmable, thereby allowing an external source to vary the background threshold value used to eliminate the selected video signals which represent content regions of the image.

Claim 29

The method of claim 22, wherein the sampling step comprises the steps of: identifying the boundaries of a window encompassing the selected portion of the image; and generating a sample signal indicating when a received video signal is within said window.

Claim 32

The method of claim 24, wherein the generating step comprises the steps of: selectively incrementing said slow-scan counter whenever a complete raster of video signals has been processed; selectively incrementing said fast-scan counter whenever a video signal has been processed; and combining the outputs from the slow-scan counter and the fast-scan counter in a manner so as to produce a signal which is active whenever the video signal being received is within the boundaries of the window.

Claim 35

The method of claim 26, further including the step of substituting an alternate value for the sampled video signals which are bypassed.

Claim 38

The method of claim 28, wherein the step of calculating a weighted running average of the magnitudes of the non-eliminated sampled video signals comprises the steps of: retrieving the magnitude of the non-eliminated sampled video signal; multiplying the magnitude of the non-eliminated sampled video signal by a first weighting factor to produce a first product; retrieving a previously stored weighted running average; multiplying the previously stored weighted running average by a second weighting factor to produce a second product; adding the first product and the second product to produce a sum which is the new weighted running average; and storing the new weighted running average for subsequent retrieval.