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= Introduction =
= Introduction =


Color vision deficiency (often called "colorblindness") affects hundreds of millions of people around the world.  The deficiency is sex linked: approximately 8% of men have a CVD versus only  0.5% of females.  This project aims to simulate the most common types of CVDs for people with normal color perception.
Color vision deficiency (often called "colorblindness") affects hundreds of millions of people around the world.  The deficiency is sex linked: approximately 8% of men have a CVD versus only  0.5% of females.  This project aims to simulate the most common types of CVDs for people with normal color perception.  The simulation will be run in realtime on an iOS device.




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== Overview ==
== Overview ==


Anomalous trichromacy can be simulated by shifting the sensitivity of the L, M, and S cones in the following ways[[#cvd |1]]:
Simulation steps are as follows:


* Protanomaly - Shift L cone toward M cone (<math>L(\lambda)_a = L(\lambda +\Delta \lambda_L)</math>)
* Precompute matrices mapping from RGB to opponent color space for range of CVD types and severities.
* Deuteranomaly - Shift M cone toward L cone (<math>M(\lambda)_a = M(\lambda +\Delta \lambda_M)</math>)
* Linearize RGB values from input camera in preparation for calculations in LMS space.
* Trianomaly - Shift S cone (<math>S(\lambda)_a = S(\lambda +\Delta \lambda_S)</math>)
* Multiply linear RGB value with opponent CVD matrix to get opponent color space representation of what a color deficient person receives as input to their neural pathways.
* Multiply deficient opponent colorspace representation by the inverse opponent matrix conversion of a normal color perceiver to get trichromat representation.
* Reapply gamma and display on screen.


== Computations ==


Anomalous trichromacy can be simulated by shifting the sensitivity of the L, M, and S cones in the following ways[[#cvd |1]]:


= Results - What you found =
* Protanomaly - Shift L cone toward M cone <math>L(\lambda)_a = L(\lambda +\Delta \lambda_L)</math>
 
* Deuteranomaly - Shift M cone toward L cone <math>M(\lambda)_a = M(\lambda +\Delta \lambda_M)</math>
== Retinotopic models in native space ==
* Trianomaly - Shift S cone: <math>S(\lambda)_a = S(\lambda +\Delta \lambda_S)</math>
Some text. Some analysis. Some figures.


== Retinotopic models in individual subjects transformed into MNI space ==
Some text. Some analysis. Some figures.


== Retinotopic models in group-averaged data on the MNI template brain ==
Some text. Some analysis. Some figures. Maybe some equations.




=== Equations===
= Results - What you found =
If you want to use equations, you can use the same formats that are use on wikipedia. <br>
''See wikimedia help on  [http://meta.wikimedia.org/wiki/Help:Displaying_a_formula formulas] for help.'' <br>
This example of equation use is copied and pasted from [http://en.wikipedia.org/wiki/Discrete_Fourier_transform wikipedia's article on the DFT].
 
The [[sequence]] of ''N'' [[complex number]]s ''x''<sub>0</sub>, ..., ''x''<sub>''N''−1</sub> is transformed into the  sequence of ''N'' complex numbers ''X''<sub>0</sub>, ..., ''X''<sub>''N''−1</sub> by the DFT according to the formula:
 
:<math>X_k = \sum_{n=0}^{N-1} x_n e^{-\frac{2 \pi i}{N} k n} \quad \quad k = 0, \dots, N-1</math> 
           
where i is the imaginary unit and <math>e^{\frac{2 \pi i}{N}}</math>  is a primitive N'th [[root of unity]]. (This expression can also be written in terms of a [[DFT matrix]]; when scaled appropriately it becomes a [[unitary matrix]] and the ''X''<sub>''k''</sub> can thus be viewed as coefficients of ''x'' in an [[orthonormal basis]].)
 
The transform is sometimes denoted by the symbol <math>\mathcal{F}</math>, as in <math>\mathbf{X} = \mathcal{F} \left \{ \mathbf{x} \right \} </math> or <math>\mathcal{F} \left ( \mathbf{x} \right )</math> or <math>\mathcal{F} \mathbf{x}</math>. 
 
The '''inverse discrete Fourier transform (IDFT)''' is given by
 
:<math>x_n = \frac{1}{N} \sum_{k=0}^{N-1} X_k e^{\frac{2\pi i}{N} k n} \quad \quad n = 0,\dots,N-1.</math>


== Retinotopic models in group-averaged data projected back into native space ==
Some text. Some analysis. Some figures.




= Conclusions =
= Conclusions =


Here is where you say what your results mean.
Applying the previously described color vision deficiency simulation to a realtime device yielded and interesting and hopefully useful


= References =
= References =


<span id="fernandes">[1]</span>[http://www.inf.ufrgs.br/~oliveira/pubs_files/CVD_Simulation/Machado_Oliveira_Fernandes_CVD_Vis2009_final.pdf Gustavo M. Machado, Manuel M. Oliveira, and Leandro A. F. Fernandes "A Physiologically-based Model for Simulation of Color Vision Deficiency". IEEE Transactions on Visualization and Computer Graphics. Volume 15 (2009), Number 6, November/December 2009. pp. 1291-1298.]
<span id="fernandes">[1]</span>[http://www.inf.ufrgs.br/~oliveira/pubs_files/CVD_Simulation/Machado_Oliveira_Fernandes_CVD_Vis2009_final.pdf Gustavo M. Machado, Manuel M. Oliveira, and Leandro A. F. Fernandes "A Physiologically-based Model for Simulation of Color Vision Deficiency". IEEE Transactions on Visualization and Computer Graphics. Volume 15 (2009), Number 6, November/December 2009. pp. 1291-1298.]
Software


= Appendix I - Code and Data =
= Appendix I - Code and Data =


==Code==
Will update with link to app store upon approval (any day now!).
[[File:CodeFile.zip]]
 
==Data==
[[File:DataFile.zip | zip file with my data]]




[http://white.stanford.edu/teach/index.php/Psych221-Projects-2011#Projects_Wiki_Pages Back to Main Page]
[http://white.stanford.edu/teach/index.php/Psych221-Projects-2011#Projects_Wiki_Pages Back to Main Page]

Revision as of 04:38, 19 March 2011

Introduction

Color vision deficiency (often called "colorblindness") affects hundreds of millions of people around the world. The deficiency is sex linked: approximately 8% of men have a CVD versus only 0.5% of females. This project aims to simulate the most common types of CVDs for people with normal color perception. The simulation will be run in realtime on an iOS device.


Background

Color vision deficiencies are characterized by reduced sensitivity to color as a result of anomalies in the eye's color receptors (called cones). In extremely rare cases, the cones in the eye are either completely absent or totally dysfunctional which results in monochromacy (no color perception). When only one cone is missing a person is said to be dichromatic. The most common CVDs are caused by a shift in the sensitivity of one of the types of cone in the eye and is known as anomalous trichromacy.

CVDs are classified according to which cone type is affected:

  • Protanomaly - L cone sensitivity is defective.
  • Deuteranomaly - M cone sensitivity is defective.
  • Tritanomaly - S cone sensitivity is defective.

Likewise, someone with dichromatic vision is completely missing either their L, M or S cones, and is called either a protanope, deuteranope, or tritanope, respectively.

Protanopia and deuteranopia reduce senstivity to red-green colors, while tritanopia reduces sensitivity to blue-yellow colors.


Methods

Overview

Simulation steps are as follows:

  • Precompute matrices mapping from RGB to opponent color space for range of CVD types and severities.
  • Linearize RGB values from input camera in preparation for calculations in LMS space.
  • Multiply linear RGB value with opponent CVD matrix to get opponent color space representation of what a color deficient person receives as input to their neural pathways.
  • Multiply deficient opponent colorspace representation by the inverse opponent matrix conversion of a normal color perceiver to get trichromat representation.
  • Reapply gamma and display on screen.

Computations

Anomalous trichromacy can be simulated by shifting the sensitivity of the L, M, and S cones in the following ways1:

  • Protanomaly - Shift L cone toward M cone L(λ)a=L(λ+ΔλL)
  • Deuteranomaly - Shift M cone toward L cone M(λ)a=M(λ+ΔλM)
  • Trianomaly - Shift S cone: S(λ)a=S(λ+ΔλS)



Results - What you found

Conclusions

Applying the previously described color vision deficiency simulation to a realtime device yielded and interesting and hopefully useful

References

[1]Gustavo M. Machado, Manuel M. Oliveira, and Leandro A. F. Fernandes "A Physiologically-based Model for Simulation of Color Vision Deficiency". IEEE Transactions on Visualization and Computer Graphics. Volume 15 (2009), Number 6, November/December 2009. pp. 1291-1298.

Appendix I - Code and Data

Will update with link to app store upon approval (any day now!).


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