Chromatic Glass

Version 3.0

How to Use

Chromatic Glass helps people with color vision deficiency (protan, deutan, and tritan types) tell colors apart more easily.
It changes colors of the device camera image or of an image file from Photos in real time. It changes only the necessary parts, keeping the original colors as much as possible, so that colors that are hard to tell apart look clearly different.
The app has a Settings screen, restores the last state, supports text size settings, and supports VoiceOver and TalkBack.

Three Modes

Switch the three modes with the Mode Tab at the very bottom of the screen (at launch, the app opens in the mode you used last).

• Distinguish Color　For telling apart colors that are hard to distinguish. This is the mode at the first launch.
• Find Color　For finding colors similar to the cursor color, or to one of the basic 11 colors, in the image.
• Simulation　Calculates how people of the P, D, and T color vision types may see colors, and shows it to people with common color vision (type C). It helps to understand which colors are hard to distinguish.

The Main Screen

All fundamental operations are performed on the main screen. It has status texts at the top, buttons on the left and right of the upper half, and the parts for each mode at the bottom. When you do not touch the screen for 10 seconds, all texts and buttons disappear except the cursor, the color name pop-up, the chromaticity diagram, and the basic 11 colors ribbon. Tap the screen once to show them again.

Status texts at the top

• Upper left: the color zone (the range of colors that are changed) as "Start~End". In Distinguish Color, an R at the end means the zone is reversed. In Find Color, it shows the searching radius. In Simulation, it shows the simulation color vision type.
• Upper center: the color vision type. The second line shows the zoom ratio.
• Upper right: the color change as "Variation/Direction". A B after the variation means Boost Mode. In Simulation, it shows the simulation strength.

Buttons at the top (left column and right column)

• Settings　Opens the Settings screen.
• Color Name　Shows the name of the color under the cursor (the color name pop-up).
• Chromaticity Diagram　Shows an xy or u'v' chromaticity diagram at the lower left. Choose which in Settings (the button's picture also changes to the shape of the chosen diagram). The small ring on the diagram is the position of the color under the cursor.
• Simulation　Shows the image changed in Distinguish Color or Find Color as it may appear for the simulation color vision type and strength. (When the screen is not tall enough, this button is hidden.)
• Save　Saves the currently displayed image, after the color change, to Photos.
• Switch Input　Chooses the rear camera, the front camera (if available), or an image file from Photos.
• Light　Turns the camera light on. Press again to turn it off. Unavailable on devices without a light, while frozen, or for image files (hidden when the screen is not tall enough).
• Freeze　Stops the video. Press again to resume. Unavailable for image files.

"Distinguish Color" Mode

This mode makes colors that people of the P, D, and T types tend to confuse easier to tell apart. The app builds "color zones" along the confusion lines (lines connecting confused colors), and changes the colors in the zone into the most distinguishable ones, keeping the original colors as much as possible. Zones and changes are calculated in a perceptually uniform color space (CIELUV).
The changed image is shown alternately with the original image, so the changed parts look as if they blink (0.33 seconds changed, 0.5 seconds original).

The toolbar

• Left "↑"　Opens the preset menu. After you choose one and confirm, its parameters are loaded. Long-press an item to save the current parameters to that preset.
• Zone Range Slider　Sets the range of colors to change. It has two thumbs, left and right; hold the part between them (blue) to move the whole range. The far left (0.0) is the side containing green, and the far right (1.0) is the side containing red (for type T, blue on the left and green on the right). Double-tap to turn the range on and off (width 0 and the former width).
• Right "↑"　Opens or closes the color change slider and the color vision type selector.

Color Change Slider (opened with the right "↑")

• Move the thumb inside the circle. The distance from the center is the variation (0.0 to 0.5), and the clockwise angle from the top is the direction (0.0 to 1.0). The color of the disc shows how a middle gray changes when you put the thumb there.
• Double-tap the thumb to turn Boost Mode on and off. When on, the disc becomes darker and the thumb becomes gold.

Color Vision Type Selector

Chooses the color vision type that is hard to distinguish (P, D, or T). It is linked with "Color Vision Type" in Settings.

"Find Color" Mode

Changes only the colors close to the cursor color, so you can find similar colors in the image. "Close" here ignores the difference in brightness and uses closeness of hue (a bright yellow and a dark yellow are close). The distance is measured in u'v' chromaticity.

• Cursor　Tap the screen to move the cursor. The color under it becomes the color to search for.
• Munsell Ribbon (Basic 11 Colors)　A ribbon of 11 colors: achromatic (N), red (R), yellow-red (YR), yellow (Y), yellow-green (GY), green (G), blue-green (BG), blue (B), purple-blue (PB), purple (P), and red-purple (RP). Tap a color to search for it. The colors are calculated at run time from Munsell notation (they are not images), and are shown in the display color space (sRGB or Display P3).
• Left "↑"　Opens the menu of the same 11 colors as the Munsell ribbon. The color you choose becomes the color to search for.
• Searching Radius Slider　Sets how far from the color to search. A small value finds only close colors, and a large one also finds different colors. The value 1.0 corresponds to 0.1 in u'v'. Double-tap to turn it on and off.
• Right "↑"　Opens or closes the color change slider and the color vision type selector. Their values are independent of Distinguish Color. This mode has no Boost Mode.

"Simulation" Mode

Makes an image showing how people of the selected color vision type may see the input image.

• Color Vision Type (C, P, D, T)　The type to simulate. C shows the original image.
• Strength Slider　0.0 means no simulation and 1.0 means full simulation. In between, the original and the simulated image are blended. The simulation strength is a value for showing the intermediate image between the color appearance of the most severe form of dichromacy of each type (100%) and the original image (0%). It does not simulate the color appearance of anomalous trichromacy (mild color vision deficiency).
• When you turn on the Simulation button (eye) at the top, the results of Distinguish Color and Find Color are also simulated with the settings of this mode.

Color Names (Color Cursor)

Turn on "Color Name" at the top (or "Show Color Name" in Settings) to show the cursor and the name of the color under it. Choose the content of the four lines in Settings (CIELAB, Oklab, CIELUV, RGB, XYZ, xyY, Munsell, JIS systematic and traditional color names, ISCC-NBS systematic names, TCCA traditional names, or none).
The color under the cursor is a weighted average over about 5 by 5 pixels (Gaussian filter). Values and names assume the image is in sRGB under a D65 light source, and follow the standards, but they are not necessarily accurate.

Chromaticity Diagram

When the "Chromaticity Diagram" button at the top is on, a chromaticity diagram (a triangle) is shown at the lower left. In Settings, "Chromaticity Diagram" chooses between the xy diagram and the u'v' diagram.

• The triangle is the range of colors the screen can show (the gamut). The colors inside the diagram are the colors of those chromaticities.
• The small ring on the diagram is the position of the color under the cursor. It moves when you move the cursor.
• The diagram is only drawn on top of the screen. It is not affected by color changes, and is not included in saved images.

Presets

A preset stores the parameters of "Distinguish Color" (the zone start and end, the strength and direction of the color change, and the five switches) as one set. You can keep up to eight sets. If you make a set for each color or situation you want to tell apart (for example, looking for a red object, or looking at an outdoor scene), you can switch between them at once without setting everything up again.

How to use a preset

1. 1. In "Distinguish Color", tap the "↑" button on the left of the bottom bar. The preset menu opens (from "1: name" to "8: name").
2. 2. Tap the preset you want. There is no confirmation: the parameters of the preset are loaded at once and replace the current ones (the color vision type does not change).

Saving the current parameters

Press and hold an item in the menu for about two seconds. A confirmation appears; tap OK and the current parameters are saved to that preset (the old values are lost).

Initial values (eight sets)　The names, and part of the zone positions, differ between types P and D and type T.

• 1　Brighten Red (type T: "Brighten Green")　Zone 0.80 to 1.00, strength 0.20.
• 2　Darken Green (type T: "Darken Blue")　Zone 0.00 to 0.25, strength 0.20.
• 3　Brighten Red / Darken Green (type T: "Brighten Green / Darken Blue")　The zone is reversed, so the outside of 0.25 to 0.80 (both ends) is changed. Strength 0.20.
• 4　Dist. Orange and YellowGreen (type T: "Dist. Green and PurpleGreen")　The zone is placed near the achromatic colors (white and gray) and reversed. Strength 0.45, direction 0.20, and the achromatic zone is not kept.
• 5　Auto Color Zone / 0.2 / Bright　Auto Color Zone is on. A zone of width 0.2 follows the color under the cursor. Strength 0.20.
• 6　Yellow WarmCol. / Blue ColdCol. (type T: "Redden Green / BlueGreen Blue")　The whole zone (0.00 to 1.00), strength 0.40, direction 0.25, Boost Mode on.
• 7　Blue Cold Colors (type T: "Redden B, BP, P, RP")　Zone from 0.00 to the achromatic position, strength 0.25, direction 0.75, Boost Mode on.
• 8　No Change　Strength 0. The colors are not changed.

The "Preset Parameters" screen　Open "Preset Parameters" in Settings to see the list of the eight sets. Choose one to edit the following items.

• Preset Name　The name shown in the menu. If you leave it empty or make it the same as the initial name, it returns to the initial name. A short, clear name makes it easy to find in the menu. Spaces at the start and end are removed when the name is saved.
• Color Zone Start / End (0.00 to 1.00)　The range of colors to change. They correspond to the two handles of the zone range slider.
• Variation (distance) (0.00 to 0.50) and Direction (angle) (0.00 to 1.00)　They correspond to the distance from the center and the angle of the circular slider for the color change.
• The five switches　Auto Color Zone, Reverse Color Zone, Inversion on Both Sides, Keep Achromatic Zone, and Boost Mode. Their meanings are the same as in "Color change options" in Settings above.

The three buttons (each one shows a confirmation when you tap it)

• Use This Preset Immediately　Loads the parameters of this preset and switches to "Distinguish Color". The current parameters are replaced.
• Save Current Parameters Here　Saves the parameters currently used in "Distinguish Color" to this preset (the old values are lost; the name does not change).
• Reset Parameters to Default　Returns the name and the values of this preset to the initial ones.

The presets are kept even after you quit the app. The app does not overwrite the switches with Preset 1 at every launch. It restores the state at the last exit (mode, color vision type, and all parameters) as it was.

Gestures

• Tap　Moves the cursor. When the controls are hidden, shows them.
• Double-tap　Resets zoom, pan, and the cursor. On the zone range slider or the searching radius slider, turns the range on and off. On the thumb of the color change slider, switches Boost Mode.
• Pinch　Zooms in and out (up to 500%).
• Pan　Moves the image while frozen or when the image is from a file.
• Long press　Freezes after 1 second (can be turned off in Settings).
• Volume buttons　When turned on in Settings, the device volume buttons also save the image.

Saving Images

The Save button saves the currently displayed image, after the color change, to Photos. Whatever the blinking phase is, the saved image is always the one after the color change. When "Embed Text in Saved Images" in Settings is on, the mode and the parameters (mode name, color vision type, zoom, zone, color change, and so on) are written at the top of the image. Location is not saved. The color space follows "Color Space" in Settings (with Automatic, images are saved in Display P3 on screens that support it).

Settings

• Embed Text in Saved Images　See "Saving Images" above.
• Color Changing Options　Color Vision Type (P, D, or T); Auto Color Zone (centers the zone on the cursor color; the zone range slider turns yellow); Reverse Color Zone (changes the outside of the chosen range; for example, with 0.3 to 0.5, it changes 0.0 to 0.3 and 0.5 to 1.0); Inversion on Both Sides (turns the color change direction by 0.5 for colors on the green side of achromatic); Keep Achromatic Zone (does not change colors near white and gray); Boost Mode (a strong change that moves colors close to spectral lights: 575 nm and 475 nm for types P and D, 660 nm and 485 nm for type T).
• Controls　Freeze on Long Press, Save on Volume (iOS 17.2 or later), Cont. Auto Focus OFF, the Chromaticity Diagram (xy or u'v'), and Zone Allocation (see the next item).
• Zone Allocation　Chooses how the value of the zone range slider decides which colors are changed in "Distinguish Color". Chart Angle Method (the default, the same as 2.21) uses the angle on the chromaticity diagram. Color Appearance Gap Method uses the distance between the original color and the color moved along the confusion line (including the difference in lightness). Chroma Gap Method uses the same kind of distance by hue and saturation only, regardless of lightness. With a different method, the same slider value changes different colors. The formulas and figures are on the "Theory" page of the website (the theory of Chromatic Glass 3.0, section 6).
• Color Name Display　Turns color names on and off, and sets the four lines of the pop-up.
• Sound　The save sound on and off and its volume, and vibration.
• Color Space　Automatic (Display P3 on screens that support a wide gamut) or sRGB.
• Preset Parameters　See "Presets" above.
• Others　Reset (resets all settings, the state, and the presets to the initial values), How to Use (shows this manual), and Privacy Policy.
• Application Info.　Shows the version and the copyright.

VoiceOver and TalkBack

The app supports screen readers. It gives names and states to the buttons, sliders, the Mode Tab, the color vision type selector, and the pop-up menus. Sliders can be increased and decreased with the screen reader actions. When the controls are hidden, the app tells you to tap the screen to show them. Text follows the text size setting of the device (texts and buttons over the video have an upper limit so that they do not become too large).

Troubleshooting

• No image is displayed.　If camera access is not allowed, allow it in Settings > Privacy on the device (App permissions on Android).
• Cannot save.　If adding photos is not allowed, allow Photos on the same screen.
• The colors do not change as expected.　Check the color vision type (P, D, T), the zone range, and the variation and the direction. Also check that "Reverse Color Zone" and "Auto Color Zone" in Settings are not on by mistake.

Others

• This application software was developed by Kazunori Asada (MD, PhD in Media Design) and is released free of charge.
  
• Color changes are made on color zones based on confusion lines, in a perceptually uniform color space (CIELUV). Simulation images are based on the method proposed in the following paper.
  H. Brettel, F. Viénot, and J. D. Mollon: Computerized simulation of color appearance for dichromats, Journal of the Optical Society of America A, vol.14, no.10, pp.2647-2655 (Oct. 1997).
  
• Changed images and simulation images are calculated under specific methods and conditions, and do not necessarily show how colors look exactly. Please use them as a rough guide.
  
• Color names shown are calculated under specific assumptions according to the standards, and are not necessarily accurate. How they look also depends on the color of the device screen.
  
• Terms such as "P type", "D type", and "T type" used in this manual are academic terms.
  
• Details of the theory are on the "Theory" page of the website.
  
• The Android version and the iPhone/iPad version behave the same (the differences are only where "iOS 17.2 or later" and the like are written above).
  

Licenses

Chromatic Glass uses the open-source software and font listed below. The full license texts are in the second half of this section.

Components and copyright notices

• Android Jetpack (AndroidX, Compose, CameraX): Copyright The Android Open Source Project (Apache-2.0)
• Kotlin standard library, kotlinx (coroutines, serialization, atomicfu): Copyright JetBrains s.r.o. and Kotlin Programming Language contributors (Apache-2.0)
• JetBrains annotations: Copyright JetBrains s.r.o. (Apache-2.0)
• Dagger: Copyright Google, Inc. (Apache-2.0)
• AutoValue annotations: Copyright (C) 2012 Google, Inc. (Apache-2.0)
• JSpecify: Copyright The JSpecify Authors (Apache-2.0)
• Jakarta Inject: Copyright Eclipse Foundation and the respective authors (Apache-2.0)
• javax.inject (JSR-330), Guava ListenableFuture: Apache-2.0
• libyuv (included in CameraX): Copyright 2011 The LibYuv Project Authors. All rights reserved. Licensed under BSD-3-Clause.
• Roboto Bold font (a subset of Latin characters): Copyright 2011 Google Inc. All Rights Reserved. (Apache-2.0)

Sources of the color name data: NBS Circular 553 (ISCC-NBS); NBS Special Publication 440 (the figures of the ISCC-NBS regions); Kelly, J. Res. NBS 61(5), 1958 (the central notations of the ISCC-NBS color-name blocks); NBS Research Paper RP1700 (Reimann, Judd and Keegan, 1946; the TCCA standard color cards). All are publications of the U.S. National Bureau of Standards (NBS).

The full texts of the Apache-2.0 and BSD-3-Clause licenses follow.

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