In case someone cares, the code below is an example of replacing the gui chosen effects of a slideshow component with the one asked for. The slideshow component is expected to be named slideshow1. Remus' example is great, performs better (less cpu load) and only requires flash 7. The code below is just to show it's possible to add a custom effect to the slideshow component. Most code is used to create the bitmap image representing the effect.
Code:
// effect code
sw = slideshow1._miw;
sh = slideshow1._mih;
bs = 50;
cols = Math.ceil(sw / bs);
rows = Math.ceil(sh / bs);
_global.KC8_Transit0 = new flash.display.BitmapData(sw + 1,sh + 1,false);
mf = 255 / ((cols-1) * 5 + bs / 2 - 1);
for (col = 0; col < cols; col++){
for (i = 0; i < bs / 2; i++){
KC8_Transit0.fillRect(new flash.geom.Rectangle(col * bs + i, i, bs - i * 2, bs - i * 2),(col * 5 + bs / 2 - i - 1)*mf);
}
}
for (row = 0; row < rows; row++){
KC8_Transit0.copyPixels(KC8_Transit0, new flash.geom.Rectangle(0,0,cols * bs, bs),new flash.geom.Point(0,row * bs));
}
// assign user effect to slides
slideshow1.onLoad = function(){
for (var i = 0; i <= this._lastslide; i++) this._slides[i][0] = 0xf80ffcc0;
}