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Re: Measuring colours accurately in mobile apps

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From: Abi James
Date: Jun 23, 2021 1:01AM

On iOS there is an app called Color Contrast (https://apps.apple.com/gb/app/color-contrast/id1095478187) that allows you to identify colours at a pixel level and calculate contrast either from screenshots (for apps) or websites directly. Used be free but now has small monthly charge.

I generally test with that and if colours are close to failing then I ask the developer and design to share HEX codes to confirm (in part to make sure they agree as sometimes the wrong colour has been used).

Abi James

Sent from my iPhone

On 23 Jun 2021, at 06:03, Steve Green < <EMAIL REMOVED> > wrote:

CAUTION: This e-mail originated outside the University of Southampton.

Does anyone have a method for accurately measuring the text and background colours in mobile apps in order to make colour contrast measurements? For context, we are independent testers, so we never have access to the development environment. Sorry this is a bit long, but it's perhaps the most challenging test process issue we currently have.

Aside from an accessibility scanner app for Android, I am not aware of any tools that can make the measurements on a mobile device. All the methods we have tried involve making the measurements on a desktop machine, which means transferring an image of the device screen.

We have done extensive testing and found that every method we can think of is wildly inaccurate. Such methods include:

* Taking screenshots and emailing them as attachments.
* Taking screenshots and emailing them as embedded images.
* Taking screenshots and transferring them through the file system.
* Screen mirroring using Mobizen and Lonely Screen.
* Setting up a Zoom call between the mobile device and the desktop machine.

The key findings are:
* For any given colour in the app, each method of measurement gives a different result. The differences can be massive. None are close enough to be useful.
* For any given method of measurement, some colours might be measured fairly accurately, but the measurement of other colours is hopelessly inaccurate.

The accessibility scanner app for Android is useful, but only up to a point. It reports the colour values in combinations that do not have sufficient contrast, which is good. However, it does not report the colour values in combinations that pass. That won't bother a lot of people, but our process requires all combinations to be measured and recorded as proof of what the colours were on that day and proof that all combinations were tested.

Also, we don't have any solution for iOS and there is the issue of measuring non-text contrast.

As far as I can tell, the errors are due to compression during the mirroring or streaming process and the different colour spaces on different devices. It is also possible that the screenshot application on mobile devices introduces errors. Images may also be degraded when embedded in emails sent from mobile devices. As such, making the measurement on the mobile device would seem to be best if that's possible.

Are we the only people who don't know how to do this? What does everyone else do?

Is it possible to download an app from the App Store or Play Store and somehow pull it into XCode or another development environment in order to see all the colours? Or are there any decompilers, like we used to use to pull apart Flash movies?

Regards,
Steve Green
Managing Director
Test Partners Ltd
020 3002 4176 (direct)
0800 612 2780 (switchboard)
07957 246 276 (mobile)
020 7692 5517 (fax)
Skype: testpartners
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