Visual computing part 1

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38 Terms

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What’s the location of pixel (x,y) in memory using rgb?
3 x (y x w + x)
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What’s the location of pixel (x,y) in memory using greyscale?
(y x w + x)
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What do HSL and HSV stand for?
Hue, saturation, lightness/value.
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Fourier transform linearity
knowt flashcard image
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Fourier transform shifting
g(x) = f(x-a)
g(x) = f(x-a)
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Fourier transform modulation
g(x) = e^{iax} f(x)
g(x) = e^{iax} f(x)
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Fourier transform scaling
g(x) = f(ax)
g(x) = f(ax)
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Fourier transform differentiation
do (iw)^n for higher order derivatives
do (iw)^n for higher order derivatives
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Fourier transform convolution
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What is the relation between focus(f), object distance(u), and image distance(v)
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What are the two types of image sensor?
CCD and CMOS
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How do LCD displays work?
Twist polarisation, max energy = 90 degress, min light
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How do we workout total number of colour for an 8-bit image?
knowt flashcard image
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How do we distribute quantisation error over multiple pixels?
Error diffusion!
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What is a horizontal gradient sobel filter?
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What is a vertical gradient sobel filter?
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What is a diagonal gradient sobel filter?
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How does erosion work?
Only keep a pixel white if all surrounding pixels are white.
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What is opening?
erosion then dilation
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What is closing?
dilation then erosion
21
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What is euler’s formula?
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What is the Fourier transform useful for?
* Low and high pass filtering
* Linear filtering
* Removing structured noise
* Compression
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What is the complexity of the fourier transform?
naive O(n^2), can split into two inputs of size n/2 which gives us O(n \\log n)
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What is uniform scaling?
Scalar is the same for each component (axis)
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Formula for anti-clockwise rotation?
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Formula for clockwise rotation?
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Formula for shear/skew
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What are projective transformations? How do we do them?

1. Parralel lines are not preserved
2. Fill in the bottom row of transformation matrix
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What is the formula for a 3d rotation about x axis?
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What is the formula for a 3d rotation about y axis?
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What is the formula for a 3d rotation about z axis?
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How do we project a 3d transformation through a pinhole onto the image plane?

1. Apply the transformation based of the focal length, and then transform so the result is in the top right, this is called the **intrinsic camera matrix**.
2. We then add a 3d transform from world to camera-co-ordinates.
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What is the difference between perspective and orthographic projection?
Perspective parralel lines don’t stay parallel, orthographic they do
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What are the different ways we can represent 3d projections?
* 3x3 matrix, not a minimal representation
* Euler angles, minimal parametisation, has gimbal lock
* Axis- angle, no gimbal lock minimal representation
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What is openGL?
is cross-language/platform and is most widely used and supported
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What is webGL?
is a JavaScript API this is based on OpenGL but can run in browser and dosen’t need to be compiled
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What is three.js?
is an easier to use wrapper for webGL.
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