Radial gradient fill

I first tried using gradient fills (via the beginGradientFill method of the Graphics class) in Bug Tunnel Defense. I wanted to use them for shading along the tunnels but could never get them to work, and eventually did it the long way by drawing a series of differently coloured rectangles. The problem was the createGradientBox Matrix function, which no matter what I passed to it would never return the right matrix for a linear fill.

BitmapData recolouring

There are at least four straightforward ways to recolour BitmapData. They all work by modifying the data directly, so the resulting BitmapData can be used as any other. Because of this they have no rendering cost, and so can be used fairly freely without impacting runtime performance.

Why BitmapData?

One topic I've seen discussed a few times online is what the best format for graphics in Flash is. And the answer is almost always the Bitmap and BitmapData classes. The overriding reason for this is performance, but it is worth looking at the alternatives to consider why this might be.

More on copyPixels

Yesterday I mentioned that the BitmapData function copyPixels can be used to combine image data and alpha data from two different sources. This function has a number of uses, in addition to adding transparency to images that don't have any.

JPEG data with alpha

The GIF and PNG graphics formats have alpha channels but JPEG does not. There may be times though when it's useful to load JPEG data with an alpha channel. Here's how.

Drawing a bitmap

This is something I've found very useful for both prototyping and making final art. The idea is to use vector drawing commands to create a bitmap, or more precisely a BitmapData. This can then be instanced hundreds or even thousands of time very cheaply, much more so than using drawing commands.