Planar Orientation from Blur Gradients in a Single Image Scott McCloskey Honeywell Labs Golden Valley, MN, USA Michael Langer McGill University Montreal, QC, Canada
Apr 01, 2015
Planar Orientation from Blur Gradients in a Single Image
Scott McCloskey
Honeywell Labs
Golden Valley, MN, USA
Michael Langer
McGill University
Montreal, QC, Canada
OutlineIntroductionRelation to Previous WorkModelling the Blur GradientPlanar Orientation Estimation Algorithm◦Estimating Tilt◦Estimating Slant
Test Data and Experimental Results
IntroductionA focus-based method to recover the
orientation of a textured planar surface patch from a single image
Relation to Previous WorkDepth from DefocusShape from Texture◦Distance effect◦Foreshortening effect
Modelling the Blur Gradient(1/3)The goal of planar orientation algorithms
is to accurately estimate the slant and tilt of a 3D plane
Modelling the Blur Gradient(2/3)Visible surface is a plane of depth
The slant and tilt are the same at all positions in the image patch
• Focal length :f• The distance from the sensor plane to the lens: sd
Modelling the Blur Gradient(3/3)
• camera’s aperture :F• focal length: f• sensor distance: • blur radius: • image position: (x,y)
sd
• is a linear function of inverse depth
• blur radius is a linear function of image position (x, y) • the blur gradient
Planar Orientation Estimation Algorithm(1/3)Image blur is best observed in the middle
to high spatial frequencies◦remove low frequencies by low pass filter
Comparing the blur along different lines in an image◦Sharpness measure
Planar Orientation Estimation Algorithm(2/3)Estimating Tilt◦Equifocal contour
A contour along which the amount of optical blur remains constant
◦Fnding surface tilt searches for the direction in which the sharpness gradient is maximized
Estimating Slant◦Slant is estimated as the angle whose back-
projection◦Produces the smallest gradient in the
sharpness measure in the direction of former depth variation
◦Uniformly blurred image (“doubly blurred image ”)
Perspective- induced size change
Test Data and Experimental Results(1/4)Test set: 1404 camera images◦9 planar textures◦26 carefully-controlled orientations◦6 different apertures
(F = 22, 16, 11, 8, 5.6, 4)26 planar orientations(Table 1.)
Test Data and Experimental Results(2/4)Orientation Estimation Results
Test Data and Experimental Results(3/4) Experiments with Image Size
Test Data and Experimental Results(4/4)Experiments with Natural Images