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<math>\left[ \begin{array}{c} X \\ Y\\Z \end{array} \right] = \begin{bmatrix} a & b & c \\ d & e & f \\ g & h & i \end{bmatrix} \times \left[ \begin{array}{c} R^{\alpha} \\ G^{\alpha} \\ B^{\alpha} \end{array} \right]</math> | <math>\left[ \begin{array}{c} X \\ Y\\Z \end{array} \right] = \begin{bmatrix} a & b & c \\ d & e & f \\ g & h & i \end{bmatrix} \times \left[ \begin{array}{c} R^{\alpha} \\ G^{\alpha} \\ B^{\alpha} \end{array} \right]</math> | ||
| − | + | Where $R$, $G$, $B$ are red, green, and blue inputs in the range $0$ to $255$ that are used to modulate physically realizable color primaries. | |
<math>p_{0}(n) = \sum_{m=-\infty}^{\infty}x(m,n)</math><br> | <math>p_{0}(n) = \sum_{m=-\infty}^{\infty}x(m,n)</math><br> | ||
Revision as of 12:36, 2 December 2015
Communication, Networking, Signal and Image Processing (CS)
Question 5: Image Processing
August 2015
Question
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Problem 1. (50 pts)
Consider the emissive display device which is accurately modeled by the equation
$ \left[ \begin{array}{c} X \\ Y\\Z \end{array} \right] = \begin{bmatrix} a & b & c \\ d & e & f \\ g & h & i \end{bmatrix} \times \left[ \begin{array}{c} R^{\alpha} \\ G^{\alpha} \\ B^{\alpha} \end{array} \right] $
Where $R$, $G$, $B$ are red, green, and blue inputs in the range $0$ to $255$ that are used to modulate physically realizable color primaries.
$ p_{0}(n) = \sum_{m=-\infty}^{\infty}x(m,n) $
$ p_{1}(m) = \sum_{n=-\infty}^{\infty}x(m,n) $
with corresponding DTFT given by
$ P_{0}(e^{j\omega}) = \sum_{n=-\infty}^{\infty} p_{0}(n)e^{-jn\omega} $
$ P_{1}(e^{j\omega}) = \sum_{m=-\infty}^{\infty} p_{0}(m)e^{-jm\omega} $
a) Derive an expression for P0(ejω) in terms of X(ejμ,wjν).
b) Derive an expression P0(ejω) in terms of X(ejμ,ejν).
c) Derive an expression for $ \sum_{n = -\infty}^{\infty}p_0(n) $ interms of X(ejμ,ejν).
d) Do the function p0(n) and p1(m) together contains sufficient information to reconstruction the function x(m,n)? If so, provide a reconstruction algorithm; if not, provide a counter example.
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Problem 2. (50 pts)
Let r0(λ), g0(λ), and b0(λ) be the CIE color matching functions for red, green, and blue primaries at 700 nm, 546.1 nm, and 435.8 nm, respectively, and let [r,g,b] be the corresponding CIE tristimulus values. </span>
Furthermore, let f1(λ), f2(λ), and f3(λ) be the spectral response functions for the three color outputs of a color camera. So for each pixel of the camera sensor, there is a 3-dimensional output vector given by F = [F1,F2,F3]t, where
$ F_1 = \int_{-\infty}^{\infty}f_1(\lambda)I(\lambda)d\lambda $,
$ F_2 = \int_{-\infty}^{\infty}f_2(\lambda)I(\lambda)d\lambda $,
$ F_3 = \int_{-\infty}^{\infty}f_3(\lambda)I(\lambda)d\lambda $
where I(λ) is the energy spectrum of the incoming light and $ f_k(\lambda)\geq 0 $ for k = 0,1,2..
Furthermore, assume there exists a matrix, M, so that
$ \left[ {\begin{array}{*{20}{c}} f_1(\lambda)\\ f_1(\lambda)\\ f_1(\lambda) \end{array}} \right] = {\begin{array}{*{20}{c}} M \end{array}} \left[ {\begin{array}{*{20}{c}} r_0(\lambda)\\ g_0(\lambda)\\ b_0(\lambda) \end{array}} \right] $
a) Why is it necessary that $ f_k(\lambda) \geq 0 $ for k = 0,1,2?
b) Are the functions, $ r_0(\lambda) \geq 0 $, $ g_0(\lambda) \geq 0 $, and $ b_0(\lambda) \geq 0 $? If so, why? If not, why not?
c) Derive an formula for the tristimulus vector [r,g,b]t in terms of the tristimulus vector F = [F1,F2,F3]t.
d) Do functions fk(λ) exist, which meet these requirements? If so, give a specific example of such functions.
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