Motion detection camera
First Claim
Patent Images
1. A method for detecting motion in an area, from first and second digital images of that area, comprising the steps of:
- identifying in a first image, at least one cell and determining a cell gradient value by;
subdividing a first cell into first and second halves having equal numbers of pixels;
obtaining for each pixel, a value;
adding the values in the first half to reach a first sum;
adding the values in the second half to reach a second sum;
subtracting the first and second sums to calculate a difference;
adding the first and second sums to calculate a denominator;
dividing the difference by the denominator to result in the first cell gradient value;
identifying the first cell in the second image and determining a second cell gradient value in accordance with the steps for determining the first cell gradient value;
obtaining an absolute difference between the first and second cell gradient values to produce a motion index;
comparing the motion index to a threshold value, so that motion is deemed to have occurred when the index equals or exceeds the threshold value.
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Abstract
A computationally inexpensive method for determining motion in a digital image stream is disclosed. The method and its software implementation provide good performance in changing light conditions and are achieved by using gradient information between adjacent areas. This gradient is normalised using the intensity or color value of the two areas, such that changing light conditions do not affect the result. The algorithm may be set up include or exclude portions of the view scene.
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Citations
14 Claims
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1. A method for detecting motion in an area, from first and second digital images of that area, comprising the steps of:
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identifying in a first image, at least one cell and determining a cell gradient value by;
subdividing a first cell into first and second halves having equal numbers of pixels;
obtaining for each pixel, a value;
adding the values in the first half to reach a first sum;
adding the values in the second half to reach a second sum;
subtracting the first and second sums to calculate a difference;
adding the first and second sums to calculate a denominator;
dividing the difference by the denominator to result in the first cell gradient value;
identifying the first cell in the second image and determining a second cell gradient value in accordance with the steps for determining the first cell gradient value;
obtaining an absolute difference between the first and second cell gradient values to produce a motion index;
comparing the motion index to a threshold value, so that motion is deemed to have occurred when the index equals or exceeds the threshold value. - View Dependent Claims (2, 3, 4, 5, 6, 9, 10, 11, 12)
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7. Software for detecting motion in an area, from inputs comprising first and second digital images of that area, comprising program steps for:
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identifying in a first image, at least one cell and determining a cell gradient value by;
subdividing a first cell into first and second halves having equal numbers of pixels;
obtaining for each pixel, a value;
adding the values in the first half to reach a first sum;
adding the values in the second half to reach a second sum;
subtracting the first and second sums to calculate a difference;
adding the first and second sums to calculate a denominator;
dividing the difference by the denominator to result in the first cell gradient value;
identifying the first cell in the second image and determining a second cell gradient value in accordance with the steps for determining the first cell gradient value;
obtaining an absolute difference between the first and second cell gradient values to produce a motion index;
comparing the motion index to a threshold value, so that motion is deemed to have occurred when the index equals or exceeds the threshold value. - View Dependent Claims (8, 13, 14)
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Specification