TextureManager#getPixelAlpha throws exception with compressed textures about phaser

[photonstorm]

Yeah this isn't possible. We'll find a way to handle this more elegantly though!

[BenjaminDRichards]

I've added some checks to getPixel and getPixelAlpha to ensure they fail gracefully, rather than throwing exceptions.

The "impossibility" is because these methods work by drawing the texture to a 1x1 canvas, then pulling the canvas data and extracting the color channels. But a canvas can only accept data from sources compatible with the DOM: Image, Canvas, and Video. Other texture sources, such as compressed textures, render textures (using framebuffers under WebGL), etc will be rejected by the browser's Canvas API.

There are other ways to do this, but they're more complex and Phaser hasn't got them yet. A roundabout hack might be to use a RenderTexture and take a snapshot, which can pass the data back out to a DOM-compatible Image, although I haven't tested this.

For now, 0a2bede checks whether the texture source is DOM-compatible. That should give you enough to check validity yourself while we put together the next release.

[yaustar]

Awesome, thanks!