Spatial standard observer
First Claim
Patent Images
1. A method of processing an image, the method comprising:
- producing a test image;
producing a test luminance image from the test image;
producing a reference image;
producing a reference luminance image from the reference image;
producing a local mean luminance reference image as a convolution of the reference luminance image and a luminance filter function;
producing a test contrast image in the absence of temporal filtering;
producing a reference contrast image;
producing a difference image; and
producing a just noticeable difference image as a mathematical combination of the difference image,wherein the convolution is defined as confined convolution, which comprises;
receiving an image;
padding the image with zeros to provide a first intermediate image;
convolving the first intermediate image with a selected non-negative kernel function to obtain a second intermediate image;
cropping the second intermediate image to obtain a third intermediate image;
receiving said third intermediate image, I3(x,y)=PCC{K(x,y),I(x,y)}; and
forming a fourth intermediate image,defined as I4(x,y)=K(x,yc I(x,y)=PCC{K(x,y), I(x,y)}/PCC {K(x,y)/Σ
xΣ
yK(x,y),I(x,y)}.
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Abstract
The present invention relates to devices and methods for the measurement and/or for the specification of the perceptual intensity of a visual image, or the perceptual distance between a pair of images. Grayscale test and reference images are processed to produce test and reference luminance images. A luminance filter function is convolved with the reference luminance image to produce a local mean luminance reference image. Test and reference contrast images are produced from the local mean luminance reference image and the test and reference luminance images respectively, followed by application of a contrast sensitivity filter. The resulting images are combined according to mathematical prescriptions to produce a Just Noticeable Difference, JND value, indicative of a Spatial Standard Observer, SSO. Some embodiments include masking functions, window functions, special treatment for images lying on or near borders and pre-processing of test images.
13 Citations
29 Claims
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1. A method of processing an image, the method comprising:
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producing a test image; producing a test luminance image from the test image; producing a reference image; producing a reference luminance image from the reference image; producing a local mean luminance reference image as a convolution of the reference luminance image and a luminance filter function; producing a test contrast image in the absence of temporal filtering; producing a reference contrast image; producing a difference image; and producing a just noticeable difference image as a mathematical combination of the difference image, wherein the convolution is defined as confined convolution, which comprises; receiving an image; padding the image with zeros to provide a first intermediate image; convolving the first intermediate image with a selected non-negative kernel function to obtain a second intermediate image; cropping the second intermediate image to obtain a third intermediate image; receiving said third intermediate image, I3(x,y)=PCC{K(x,y),I(x,y)}; and forming a fourth intermediate image, defined as I4(x,y)=K(x,y c I(x,y)=PCC{K(x,y), I(x,y)}/PCC {K(x,y)/Σ
xΣ
yK(x,y),I(x,y)}.
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2. A method of spatially processing an image, the method comprising:
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spatially producing a test image with a test image dimension of nx pixels in the x direction (width) and ny pixels in the y direction (height) having Gtest (x,y) which is defined to be the grayscale of the pixel at column x and row y; spatially producing a reference image with a reference image dimension of nx pixels in the x direction (width) and ny pixels in the y direction (height) having Greference (x,y) which is defined to be the grayscale of the pixel at column x and row y; wherein spatially producing the test and reference images includes; providing viewing angles subtended in each image in the x and y directions defined by sx and sy respectively, the viewing angles sx, sy can be derived from a viewing distance and an image size in a display by the equation as follows, once to compute sx and once to compute sy;
tan {(π
*size(degrees)/360}=(0.5*size)/viewing distanceand providing a width and height for each pixel, px and py as follows; - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 29)
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24. A method of performing confined convolution, the method comprising:
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receiving an image; padding the image with zeros to provide a first intermediate image; convolving the first intermediate image with a selected non-negative kernel function to obtain a second intermediate image; cropping the second intermediate image to obtain a third intermediate image; receiving said third intermediate image, I3(x,y)=PCC{K(x,y),I(x,y)}; and forming a fourth intermediate image, defined as I4(x,y)=K(x,y c I(x,y)=PCC{K(x,y), I(x,y)}/PCC {K(x,y)/Σ
xΣ
yK(x,y),I(x,y)}.
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25. A method of processing a spatial image, the method comprising:
producing a spatial test image with a test image dimension of nx pixels in the x direction (width) and ny pixels in the y direction (height) having Gtest (x,y) which is defined to be the grayscale of the pixel at column x and row y; producing a spatial reference image from the spatial test image with a reference image dimension of nx pixels in the x direction (width) and ny pixels in the y direction (height) having Greference (x,y) which is defined to be the grayscale of the pixel at column x and row y; wherein spatially producing the test and reference images includes; providing viewing angles subtended in each image in the x and y directions defined by sx and sy respectively, the viewing angles sx, sy can be derived from a viewing distance and an image size in a display by the equation as follows, once to compute sx and once to compute sy;
tan {(π
*size(degrees)/360}=(0.5*size)/viewing distanceand providing a width and height for each pixel, px and py as follows;
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26. A method of spatially processing an image, the method comprising:
producing a spatial test image with a test image dimension of nx pixels in the x direction (width) and ny pixels in the y direction (height) having Gtest (x,y) which is defined to be the grayscale of the pixel at column x and row y; producing a spatial reference image with a reference image dimension of nx pixels in the x direction (width) and ny pixels in the y direction (height) having Greference (x,y) which is defined to be the grayscale of the pixel at column x and row y; wherein spatially producing the test and reference images includes; providing viewing angles subtended in each image in the x and y directions defined by sx and sy respectively, the viewing angles sx, sy can be derived from a viewing distance and an image size in a display by the equation as follows, once to compute sx and once to compute sy;
tan {(π
size(degrees)/360}=(0.5*size)/viewing distanceand providing a width and height for each pixel, px and py as follows; - View Dependent Claims (27, 28)
Specification
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Current AssigneeUnited States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
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Original AssigneeUnited States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
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InventorsWatson, Andrew B.
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Primary Examiner(s)Le, Vu
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Assistant Examiner(s)Abdi, Amara
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Application NumberUS12/807,375Publication NumberTime in Patent Office589 DaysField of Search382/286, 382/275, 382/254, 348/180, 348/189US Class Current382/279CPC Class CodesG06T 2207/30168 Image quality inspectionG06T 7/0002 Inspection of images, e.g. ...H04N 17/04 for receiversH04N 19/60 using transform codingH04N 19/86 involving reduction of codi...
