[whatwg] Colour correction (was: Canvas ImageData comments)

[Henri Sivonen]

On Jan 20, 2008, at 19:58, Darin Adler wrote:

> On Jan 20, 2008, at 9:10 AM, Henri Sivonen wrote:
>
>> Most of the time, the solutions to the color space problem are  
>> worse that the problem itself. The easiest fix for this whole mess  
>> would be making Mac OS X default to 2.2 gamma (i.e. be compatible  
>> with the overall legacy instead of the Mac legacy) and then  
>> continue to treat Web color values as being in the system color  
>> space.
>>
>> At least in order to avoid Breaking the Web, browsers need to treat  
>> all untagged colors in a mutually consistent way within a browser  
>> window regardless of the source of the color: image files, CSS,  
>> plugins, video, legacy HTML attributes, etc. The usual way to do  
>> this is to treat all untagged color values as being in the system  
>> color space.
>
>
> Good explanation.
>
> The proposal from color experts here at Apple is to interpret  
> untagged colors in the sRGB color space. This is what's done with  
> most other untagged color in Mac OS X.

It sure looks like most untagged color is taken to be in the system  
color space.

> But this rule not yet implemented in WebKit. Instead, when  
> displaying on screen, today's WebKit treats untagged color as if it  
> was in the system's primary display device's color space. This means  
> that no color correction is applied to such colors.

Yes, and the sRGB approach would Break the Web as long as the Flash  
plug-in doesn't participate.

> I'm not certain exactly what the "system" color space is

I mean the profile selected in System Preferences > Displays > Color >  
Display Profile.

> or whether the Mac OS X gamma difference from Windows is important  
> when designing this.

The gamma difference is the foremost problem being "solved" but it  
would be by far easier to solve by changing the Mac OS X default gamma  
to match Windows. Computing color space transformation just because  
Mac OS X is stuck with an unusual default gamma value is an overkill.  
Sure, there are other color space differences, but most of the time  
for most people, the non-gamma differences are less important.

> I think the sRGB design is a good one.

I disagree. Why would you want a brand new Cinema display emulate the  
gamut of an office CRT from the previous millennium potentially by  
clipping instead of stretching the colors to gamut of the device at  
hand?

> When displaying color on devices with unusual color characteristics,  
> it doesn't make sense to display color with no correction at all.

Yeah, but most Web browsing systems don't have too unusual  
characteristics except for the Mac default gamma.

-- 
Henri Sivonen
hsivonen at iki.fi
http://hsivonen.iki.fi/