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Welcome to reHue.net

How to use reHue.net
What's the point of reHue.net?
The filters
Some other color blindness resources

reHue.net is an HTML5 web app written in Javascript that allows people without colorblindness to simulate how images appear to colorblind people. reHue.net also allows you to daltonize images, which is a process that adjusts the hues in an image to make them more easily distinguished by colorblind people. Several different types of colorblindness can be simulated and adjusted for, with each function implemented as a color filter that can be selected from a drop-down list and applied to an image. A full list of the color filters that can be applied to an image is enumerated here. This site does not contain any medical information about colorblindness, nor does it offer any medical advice. It also does not contain any tests for colorblindness.

How to use reHue.net:

To open an image, first you need to return to the main page. There are several ways of getting an image into the app. The easiest is to screencap an application or webpage using the PrintScreen key or Alt-Printscreen key combination and then paste it onto the reHue.net page using Ctrl-V (or ⌘-V on a Mac). In some browsers it is also possible to copy an image from a webpage (right-click then Copy Image) and then paste it onto reHue.net. Alternatively, if your browser supports the HTML5 FileReader object you can browse for a file on your local file system, or else drag and drop an image file on to the page to open it. All the image processing in the reHue.net web app happens client-side in your web browser, so your image will not be uploaded to any server for processing.

Once the image has opened you can select a color filter from the drop-down list. By default it simulates red-green colorblindness, the most common form of colorblindness. When you choose another filter, the image will be updated immediately with the new filter. For large images this may take a few seconds.

A check-box lets you fit the image to your browser window if checked. If unchecked, the image will display at its actual size. You can click and drag the image around the screen, which is useful for scrolling around images that are larger than the browser window.

That's it!

What's the point of reHue.net?

There are plenty of excellent, functional and often free tools on the Internet for simulating colorblindness and daltonizing images. The advantages of reHue.net are that it does not require uploading images to a web server, so there are no upload file size limits and no waiting for filtered image to download from the server, and it also does not require installing a native application for your particular desktop operating system or mobile device. It can be used for all image files that can be read by the browser. However one thing it can't do is daltonize or simulate color blindness on a web page directly as you browse it (a Javascript bookmarklet that can do that is here).

I hope reHue.net is useful for someone!

The filters:

The filters that can be applied are listed below. Click on the "Show example" links for example images and more information about the filters, or click on the filter name to return to the main page to apply the filter to an image.

Normal Color Vision (No Filter)
Displays the image as-is.
Simulates various forms of color blindness. The formula used is taken from here, but the implementation is different. reHue.net uses a precalculated color table to speed up the filtering of images.

Show example
Simulates various forms of partial color blindness. This is implemented as a cross-fade between normal color vision and the simulated color blindness modes above, according to a user-supplied percentage.

Show example
Daltonizes an image to adjust for various forms of color blindness. The formula used is taken from here but as with the simulation filter the implementation is different.

Show example
Daltonizes an image to adjust for a particular form of color blindness, and then simulates how a person with that form of color blindness will perceive the daltonized image. You can compare the results with the results of the first three color blindness simulation filters in this list to get an idea of how much difference daltonization will make.

Show example
Simulate Achromatopsia (Monochromacy)
Simulates monochromacy by converting the image to greyscale. The formula is V = Red * 0.299 + Green * 0.587 + Blue * 0.114

Show example
Simulate Achromatomaly (Partial Monochromacy)
Simulates partial monochromacy using a color matrix transform to give a result intermediate between normal color vision and monochromacy.

Show example
Gamma-corrected Greyscale Image
Displays the image in greyscale. This is identical to Simulate Achromatopsia (Monochromacy), but applies a gamma power value of 2.2 to the color components before the calculation and then 1/2.2 to the greyscale value afterwards.

Show example
Color-adjusted Greyscale Image
This filter converts the image to greyscale, but takes account of the colors that are in the image and tries to avoid mapping colors with the same brightness but different hues to the same greyscale value. This means that it is possible to tell areas of different color apart in the greyscale image, even if you can't tell what colors they are. The algorithm is based on the one described in this paper.

Show example
Brightness-adjusted Daltonized Image
This filter adjusts the brightness of the colors in the image so that different hues that are easily confused by colorblind people are more easily distinguished because they are set to a different brightness.

Show example
Displays the red, green and blue channels of the image.

Show example
Displays the long, medium and short wave components of the image, normalized to have the same brightness range. In theory these correspond to the light that is detected by the three different types of cones in the human eye, roughly corresponding to red, green and blue.

Show example
Display LMS as RGB
Maps the LMS channels to RGB. This looks similar but not identical to the original image. It's not identical because the LMS channels do not exactly correspond to RGB.

Show example
Invert Colors
Inverts the colors in the image.

Show example

Some other color blindness resources:

http://www.daltonize.org

http://en.wikipedia.org/wiki/Color_blindness

http://colorvisiontesting.com

http://www.vischeck.com

http://www.wearecolorblind.com


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