+1 feature for RealWorld Photos

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+1 feature for RealWorld Photos

Published by on December 1st 2008.

The topic of color management is a one of those ugly untamed beasts. Many graphic applications choose to pretend it lives on another continent, but in reality it sits right next to you. No, the first release of RealWorld Photos will not be fully color managed. Instead, it will provide a simple solution for the most important scenario: sRGB profile.

And guess what: it even beats Photoshop in this area.

The symptoms - bad color blending

Open a graphic editor. Create a new (RGB) image, fill it with green color (by green, I mean R:0%, G:100%, B:0%). Now, draw a red anti-aliased circle over the green background. The supposed end result is a smooth red circle over a green background.

If you use white and black instead of red and green, you may notice that the edges are not as smooth as they should be.

Circles drawn with and without gamma-aware blending.

The left sides of the circles are correct while the right sides have problems. The differences are subtle, but visible. Note the dark outline of the lower right part of the red circle. Also, look closely at the black circle. The left half is smoother than the right half. I bet you want your shapes smooth…

Painting with brush with and without gamma correction.

The image above nicely demonstrates the same effect of dark outline. When painting with a smooth brush, it becomes more apparent. While the left stroke looks natural, the right one has an unwanted dark outline.

Another area, where you might have noticed incorrect results (or not if you do not care about details and blindly trust your software) is in changing image size - re-sampling. The classic techniques make areas with large difference between neighbor pixels darker than they should be.

Gamma correction brightness difference.

The diagnosis - ignoring gamma

The problem here is the fact that color profile of your display/CRT was ignored. The application assumed it was working in a linear color space, which was not true. Typical color profile, which is recommended for all web graphics (the sRGB color profile) can be approximated by a gamma correction of 2.2.

Let’s look on how a red → green color gradient looks like when colors are interpolated with gamma in mind and when gamma is ignored.

Red-Green gradients with and without gamma correction.

The left (gamma-correction of 2.2) image should actually appear linear, while the right should appear too dark in the middle due to the uncompensated correction performed by your display. This effect causes the dark outline of the circle on the upper image.

Now, typical PC and Mac displays have different gammas and viewing conditions also play a role, so do not beat me if the above images look a bit differently on your display. Instead, consider calibrating it. If you make your own graphics or edit photographs, calibration should not be neglected.

The problem - it is too complex

Professional graphic apps can do color management, but they also assume that users are aware of the problems and use the right functions at the right time. If they don’t, the results are sub-optimal.

Simple graphic apps often ignore color management and just produce incorrect images.

The problem is that if you follow the trivial procedure described above (drawing red circle over green background), many applications produce the wrong result (and yes, Photoshop gets this wrong too).

A graphic editor either does not support color management at all or the user must actively know and use the functions for color management. That’s bad.

The solution - choosing the right defaults

RealWorld Photos takes an unique approach towards solving the above problem. It does the gamma-aware color blending for you. If you are OK with the default 2.2 gamma correction, you do not need to do anything. If you want a different gamma correction, you can change it in the application options (setting it to 1 will make RealWorld Photos act just like every other application).

Color options configuration.

The advantages of RWPhotos solution

  • Simplicity - users without detailed knowledge get the right results.
  • Consistency - the color pickers show the actual colors. (Compare: if you do manual gamma correction afterward, your picked colors visually change.)
  • Accuracy - RealWorld Photos uses internally more bits for gamma-aware blending. (Compare: if you remove gamma correction, resample picture, restore gamma correction for example in Paint.NET, you’ll lose precision).

Summary

Keeping things simple for the end user is one of the core values of RealWorld Designer framework. Computers should not ask questions when the correct answer is obvious (at least under typical conditions). I am always happy when I find area, where I can apply this rule.

The upcoming version of RealWorld Photos will deliver correct results by default and will save the user the need to remember all the complicated stuff behind gamma correction. Applications are supposed to make life easier, aren’t they?

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