van eyck: follow the light
DESCRIPTION
Van Eyck: Follow the Light. Krista Kelly Kevin Ma. Advisors: Ingrid Daubechies & Rayan Saab. The Ghent Altarpiece. Finished in 1432 24 framed panels Religious painting Light source significance. Original size: [6668 4992 3] Pixels Rescaled and converted to black and white - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/1.jpg)
Van Eyck: Follow the LightKrista KellyKevin Ma
Advisors: Ingrid Daubechies & Rayan Saab
![Page 2: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/2.jpg)
The Ghent AltarpieceFinished in 143224 framed panelsReligious paintingLight source significance
![Page 3: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/3.jpg)
![Page 4: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/4.jpg)
![Page 5: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/5.jpg)
Original size: [6668 4992 3]
Pixels
Rescaled and converted to black
and white
Resized: [1111 832]
Reduced amount of data by a factor of
108
Which reduced calculation time
significantly
![Page 6: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/6.jpg)
How to Analyze the Image? There are other reflections but for
consistency and purest results- focus on one shape The pearl (dundundun…!)
Circuluar Uniform Existing codes available
Hough Gabor
![Page 7: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/7.jpg)
Canny Filter Matlab function:
e = edge(bwimage,`canny’, .5); Shows up in both Hough and Gabor
Canny .3 Canny .5
![Page 8: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/8.jpg)
Hough Transform Edge detection technique http://www.markschulze.net/java/hough/ Returns a 3-D accumulator array
Voting on circle locations & radii
![Page 9: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/9.jpg)
Hough Transform - Raw
![Page 10: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/10.jpg)
Gabor Annulus Circular wavelet filter Inputs:
Kernel Size --- 80 Wavelength (=100) --- f0
Gaussian deviation (1-10 usually) --- Radius of circle --- r
![Page 11: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/11.jpg)
Loop ControlThresholding for Gabor
![Page 12: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/12.jpg)
Gabor Annulus Without Thresholding
Gabor Annulus With Thresholding
Gabor Continued…
![Page 13: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/13.jpg)
Once the Gabor is used…Threshold
again using “loop control”
This is then put through a function called imdilate – a logical matrix that
will threshold further so we can locate the pearls.
![Page 14: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/14.jpg)
Plot of Rough Pearl Locations
![Page 15: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/15.jpg)
Plot of Thresholded Pearl Locations
![Page 16: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/16.jpg)
“Pcards” There are no Aces, Kings, or Queens.
Given the locations of where pearls may be found We create “Pcards”: small 40x40
images around each location and fill up what we call P, the deck of CARDS/images
The size of P is [40 40 #-of-cards]Sample Pcard
![Page 17: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/17.jpg)
Use and abuse the Pcards Apply the Hough Transform
Locates the relative center and radius on the Pcard
Extract the literal locations Able to cut out the pearl Now what about the light?
![Page 18: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/18.jpg)
Wedges – find the light Used two variables, alpha and delta. Cut out 20 degree wedges from -90 to
90 Average the values by summing the
pixel values and divide by the number of pixels.
Find the max If n<3, disregard
![Page 19: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/19.jpg)
Raw Angles
![Page 20: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/20.jpg)
ThresholdingWe discounted an angle using the
following rule: If the MaxValue<MeanValue*1.2Discount the angle
![Page 21: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/21.jpg)
Thresholded Angles
![Page 22: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/22.jpg)
![Page 23: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/23.jpg)
ConclusionsOur research suggests he was at least accurate enough to have a
general direction Is there more than one light source? Was he really that good? Error in our calculations is significant – The answer is still up in the air
Questions?
![Page 24: Van Eyck: Follow the Light](https://reader036.vdocuments.us/reader036/viewer/2022081418/56816733550346895ddbdfe2/html5/thumbnails/24.jpg)
References Hough Transform Code:
http://www.mathworks.com/matlabcentral/fileexchange/26978-hough-transform-for-circles
Gabor Annulus Code & Paper: http://red.cs.nott.ac.uk/~aqr//circle/ A. Rhodes and L. Bai. Circle Detection
Using a Gabor Annulus. Proceedings of the 22nd British Machine Vision Conference. Dundee, UK, 2011.