• VidCapture
• CodeBlind
• MIDI Driver
• 3D Scanner
• Mouse on a Stick!

• BETAs
• Add-ons / Configs
• Code

• Products
• Updates

• Bug Reports
• News
• People

• Bob Stein of VisiBone, for his colorblindness information page and for letting me use his palettes.
  
• The coders at Nullsoft, for an excellent free installation package.
  
• Jace of TBL, who posted great info on integer-based RGB/HSI conversions that saved me a lot of cycles.
  
• All the people who responded to my Slashdot post when I first started trying to find something to do simulations with.
  

Table of Contents:

• Disclaimer, thanks, etc.
• Overview
• Usage
• Troubleshooting
• Further Reading
• Download CodeBlind

The simulation modes are not mathematically correct, nor do they necessarily accurately model any one colorblind person. However, they are designed to help show what colors are ambiguous for various types of colorblindness to assist you in choosing good colors for your project. If you would like a mathematically correct model, please see the links under Further Reading at the end of this document.

Specifically, the model I'm using attenuates the deficient color more strongly than other models, and does so in RGB space rather than LMS space as might be appropriate for computer simulation. However, I have heard reports of people with a red deficiency having difficulties telling if a red light was on at all or seeing full red text on a black background, so perhaps it is not entirely off. Either way, additional conversions between color spaces (already doing RGB->HSI->RGB for hue shift and compression) would make the program considerably slower.

You also may want to note that it is reported in Brettel et. al (see Further Reading) and elsewhere that many people deficient in one color seem more sensitive to changes in color that affect the other two colors, which is not simulated here (only got 256 values per channel).

CodeBlind requires a modern computer with a true color (32-bit) display to run properly. While it has been heavily optimized versus previous versions, it still takes a decent amount of processing power depending on how you configure it. Please see the Usage and Troubleshooting sections if you run into problems.

To see what CodeBlind can do, take a look below. The first row of pictures from left to right show a simulated picture of colored candy, then the same picture as it might be seen with a red, green, and blue color deficiency.

Notice the difficulty contrasting yellow and green with a red deficiency, or red and yellow with a green deficiency. Now look at the pictures below. From left to right, they are the second from the above table with a green deficiency, the original candy picture modified to have a compressed and shifted hue space with CodeBlind, and a simulation of the compressed hue image as seen with a green deficiency.

This is one way that CodeBlind can enhance viewing of colors. Another way is to simply convert one of them to grey. The pictures below show the same picture with the yellow channel converted to grey, then the simulation of that viewed with a green deficiency. The colors are no longer ambiguous.

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The screenshot above shows the two CodeBlind windows: On the left is the Options window, and on the right is the Magnifier window.

The Magnifier window

To resize the Magnifier window, click on the four-way arrow at the bottom right and drag it to your desired size. You can always restore the window to its default size by pressing the "*" restore button, or by clicking on the window, then pressing ALT-R. You may also make the window larger or smaller in increments by pressing ALT-1 and ALT-2 respectively.

One last feature of the magnifier is it will display the name of the color that your cursor is currently over. There are currently 8 colors recognized:

Black	White	Grey	Red	Yellow
Green	Green	Cyan	Blue	Magenta

In addition, if the intensity is less than half the maximum, it will be called "dark". The color label describes the color of the actual pixel - NOT the transformed magnification view within CodeBlind.

To configure the Magnifier window, click on the "Configure" button along the top bar. This will bring up the Options window.

The Options Window

You can always restore the "Default" configuration just by pressing the "Reset All to Defaults".

The other controls are grouped as follows:

• Performance
• Color Control
• Configuration
• RGB Modification
• Channel Brightness
• Convert Color To Greyscale
• Simulations

Performance Controls

If you want the magnifier to always be on top of any windows, regardless of focus, click the "Magnifier Always On Top" button in the top left of the Options Window.

To increase the magnification level in the Window, click on the "Magnify" knob and drag upwards. You can decrease the magnification level by dragging the knob downwards. For finer control, you can select any knob by clicking on it or using the Tab key, then press the arrow keys to turn it (up and down for coarse adjustments, left and right for fine-tuning).

The Refresh knob controls how fast the Magnification window is refreshed. This can be set anywhere from 1Hz to 50Hz. At 50Hz, it's obviously going to look best - however, depending on your hardware it may not be able to achieve that. The faster the refresh rate, the more processor it is going to take to run well. I'd recommend bringing up Task Manager or a similar Processor monitor and try to set the refresh to a level that takes under 30% of your processor's time.

The Filter knob controls whether or not the mouse tracking is filtered. If it is, then it will appear as if the magnification window follows behind your mouse, rather than updating directly from where the mouse is each time it refreshes. This can make it quite a bit easier to make sense of mouse movement in the window, but is really only advantageous at high refresh rates.

Color Control

The Compress knob sets the Hue compression. Since hue is a circular value (from the HSI or Hue, Saturation, and Intensity model), the compression simply reduces the amount of that circle that is traveled. In other words, it reduces all of the available colors into a smaller set of colors. Using the Hue knob as an offset, this allows you to reduce the 6 major colors down to as few as you would like, avoiding colors that you may have trouble seeing.

The Gamma knob simply performs gamma correction during the transform. By default, with the knob pointing straight up, no gamma is performed. To make the Magnification Window show everything darker, turn the Gamma down. To make everything brighter, turn it up.

Configuration controls

RGB Modification controls

Channel Brightness

Convert Color to Greyscale

Simulations

The big thing is contrast - any text or important objects should have a high contrast against their background, even in situations where multiple colors may be confused. In addition, if you are designing an interface, try to use multiple types of indicators for any single message - it will make it easier on everyone. Color, shape, and text should all be used if possible. You may want to check under Further Reading for additional resources and suggestions.

At any rate, four types of color blindness are simulated. You may depress any one of the buttons at a time. To control the level of color blindness, rotate the "Severity" knob beneath the buttons.

The top two, Red and Green deficiencies, are the most common and are often grouped together as "Red/Green" color blindness. See Further Reading for osites with good explanations of each type of color blindness.

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Some likely problems are the following:

• The Magnifier window refreshes too slowly: This is generally caused by the refresh knob being turned down. The default is fairly slow to help it run right off on older computers. Just turn up the knob. However, see the following....
  
• CodeBlind takes up all my processor!: It can do that - it's doing some pretty hefty image processing and copying a lot of data around. Turn down the Refresh rate, turn up the Magnification, or make the Magnifier window smaller to reduce processor usage. I recommend a 2Ghz Pentium-class processor, 256MB of RAM, and an ATI or NVidia video card. However, it should work on considerably less if you turn it down a little....
  
• Movement is too jerky in the Magnifier window: Turn up the Refresh and/or the Filter knobs. Also, see above.
  
• Where can I get the latest version? Here.
  
• The colors seem wrong or pixelized: You may be in 256 color mode, even if your hardware supports more. Right click on the desktop, select "Properties". The "Display Properties" dialog should appear. Now click on the "Settings" tab. Make sure the "Colors" drop-down is set to "True Color (32 bit)". Click "OK". Make sure to say "Yes" if it prompts you to keep them.
  

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Vision Tests

• Ishihara dot tests
• A test for kids with information

Designing with color

• VisiBone is a great place for webmasters and other designers to get color information for web design. There's a also page there dedicated to designing to accomodate color blindness as well.
  
• Joe Clark's book, Building Accessible Websites, has an excellent section on color blindness.
  

Color Blindness Simulation, Assistance, and Information

• VisCheck simulates different kinds of color blindness, and is most likely quite a bit more mathematically correct and accurate than CodeBlind. In addition, they have a proprietary algorithm for converting images to be useable by color blind people called Daltonization, and license it for use. You can play with the algorithm on their site as well. The Stanford Office of Technology Licensing may also license Daltonization.
  
• Colorblind Web Page filter
  
• H. Brettel, F. Vienot, and J.D. Mollon
  "Computerized Simulation of color appearance for dichromats"
  Journal of the Optical Society of America A
  Volume 14, No 10. October 1997
  
  Describes the mathematics for simulation of dichromatic color blindness.
  

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