- From: Daniel Weck <daniel.weck@gmail.com>
- Date: Tue, 9 Dec 2008 00:56:04 +0000
- To: Sean Hayes <Sean.Hayes@microsoft.com>
- Cc: "public-tt@w3.org" <public-tt@w3.org>
On 8 Dec 2008, at 23:05, Sean Hayes wrote: > I notice that opacity is specified as a float value, implying an > inordinate (and completely untestable) set of gradations of alpha; > while colour alpha is specified as only 255 steps. This seems > completely skewed to me. > > I would recommend that we align opacity and colour alpha by > specifying <alpha> expressions as component-value. > > Whether we wish also to anticipate 16bit colour is a separate > question we probably ought to look at. I disagree with the "completely untestable" statement. For media and region opacity, the SMIL 3.0 specification uses percentage values in the range 0-100% or numbers in the range 0.0-1.0, with 100% or 1.0 meaning fully opaque. http://www.w3.org/TR/SMIL3/smil-extended-media-object.html#smilMediaNS-MediaOpacity The SMIL 3.0 test-suite includes tests for basic opacity as well as for more complex chromaKey processing. Testing a reference implementation does not consist in asserting every possible values, even in a discrete scenario. It is about evaluating a set of judiciously chosen parameters, such as a couple of random values as well as edge cases that can be potentially misinterpreted by the specification readers/implementors. In fact, the test-suite is not meant to test implementations of the standard, it is meant to prove (to a certain extent, as with any tests) that the specification is clear enough to be implementable consistently without ambiguity. At least that is my understanding of the role of the test-suite. In the case of SMIL 3.0, the test-suite coverage satisfies the new features brought into since 2.1. Here's 2 examples of tests (may require member access): http://www.w3.org/2007/SMIL30/testsuite/New-SMIL30/files/Layout/ColorQuad_NoText.png http://www.w3.org/2007/SMIL30/testsuite/New-SMIL30/files/Layout/ColorQuad_WithText.png http://www.w3.org/2007/SMIL30/testsuite/New-SMIL30/files/Layout/layout-background-opacity-region-override.txt http://www.w3.org/2007/SMIL30/testsuite/New-SMIL30/files/Layout/ColorGrid.png http://www.w3.org/2007/SMIL30/testsuite/New-SMIL30/files/Layout/layout-background-opacity-region.txt More to see here: http://www.w3.org/2007/SMIL30/testsuite/New-SMIL30/SMILtestsuite.html Regards, Dan
Received on Tuesday, 9 December 2008 00:56:46 UTC