Tag Archives: SVG

SVG RadialGradients

If you are interested into how radial gradients are drawn in SVG, you might want to have a look at the following file.

It shows a radial gradient, overlaid with the different features of the gradient (center, focal point and radius). It shows an animation of a circle used to compute the gradient, all points belonging to that circle, at the same instant, have the same color (see a formal definition here). In short, there are three interpolations going on: one determines the center of that construction circle, one the radius of that circle and one the color of circle stroke. If you dig in the file and uncomment the color animation, you should see that when the circle’s stroke color is animated, the stroke perfectly matches the gradient behind and is therefore not visible (inside the gradient circle).

I’ve put here another example of an edge case, when the focal point is located on the edge of the center defined by the gradient element.


GPAC Widgets Video on YouTube

I have finally had a bit of  time to post on YouTube some old videos that we did to demonstrate the combined use of the W3C Widgets Packaging and Configuration specification and of the MPEG-U Widgets standard. These videos show: simple widget managment (with different GUI styles), communication between widgets and widget migration. Let me know if you have comments. Continue reading GPAC Widgets Video on YouTube

Test suite and validation

Most standards produce test suites to demonstrate the features of the standard. This is also very useful to test implementations. GPAC also has a (very limited) test suite to test that the code does not regress. However, when the tests need to be clicked on or when there is animation, the validation of a test may get quite complex.

There are several ways to solve this problem. Erik Dahlström from Opera told me that they use additional JavaScript with specific APIs to do their regression testing. This is interesting but I’m concerned by the time it takes to author this Javascript. So I  thought about another way.

Within GPAC, I’ve implemented a small plugin which enables two things:

  • to play a test, record the interactions (in an XML file) and take PNG snapshots upon specific events;
  • and then to replay the content, reproduce the interactions and compare the snapshots to indicate if the result is valid or not.

A playlist of test sequences can then be created and the validation can be automatic. It doesn’t take much time to record the interactions, what I called the validation script.

You should see this soon on GPAC SVN.

Late news

Just for the record, in case you haven’t noticed. Our team organized two standardisation meetings this September:

We are working on both topics at the moment. We should have some demos soon.