Please help bitmap hitTesting code

programming flash
1

I have asked twice to no avail, please will somebody explain this to me in detail, as I don’t understand it:

[FONT=Courier New][LEFT][COLOR=#0000FF]import[/COLOR] flash.[COLOR=#000080]display[/COLOR].[COLOR=#000080]BitmapData[/COLOR];
[COLOR=#0000FF]import[/COLOR] flash.[COLOR=#000080]geom[/COLOR].[COLOR=#000080]Point[/COLOR];
[COLOR=#0000FF]MovieClip[/COLOR].[COLOR=#0000FF]prototype[/COLOR].[COLOR=#000080]pixelHitTest[/COLOR] = [COLOR=#000000]function[/COLOR][COLOR=#000000]([/COLOR]mc:[COLOR=#0000FF]MovieClip[/COLOR], threshold:[COLOR=#0000FF]Number[/COLOR][COLOR=#000000])[/COLOR]:[COLOR=#0000FF]Boolean[/COLOR] [COLOR=#000000]{[/COLOR]
threshold = threshold ? treshold : [COLOR=#000080]1[/COLOR];

[COLOR=#000000]var[/COLOR] thisBitmap:BitmapData = [COLOR=#000000]new[/COLOR] BitmapData[COLOR=#000000]([/COLOR][COLOR=#0000FF]this[/COLOR].[COLOR=#0000FF]_width[/COLOR], [COLOR=#0000FF]this[/COLOR].[COLOR=#0000FF]_height[/COLOR], [COLOR=#000000]true[/COLOR], [COLOR=#000080]0[/COLOR][COLOR=#000000])[/COLOR];
thisBitmap.[COLOR=#000080]draw[/COLOR]COLOR=#000000[/COLOR];
[COLOR=#000000]var[/COLOR] mcBitmap:BitmapData = [COLOR=#000000]new[/COLOR] BitmapData[COLOR=#000000]([/COLOR]mc.[COLOR=#0000FF]_width[/COLOR], mc.[COLOR=#0000FF]_height[/COLOR], [COLOR=#000000]true[/COLOR], [COLOR=#000080]0[/COLOR][COLOR=#000000])[/COLOR];
mcBitmap.[COLOR=#000080]draw[/COLOR]COLOR=#000000[/COLOR];

[COLOR=#0000FF]if[/COLOR][COLOR=#000000]([/COLOR]thisBitmap.[COLOR=#0000FF]hitTest[/COLOR][COLOR=#000000]([/COLOR][COLOR=#000000]new[/COLOR] Point[COLOR=#000000]([/COLOR][COLOR=#0000FF]this[/COLOR].[COLOR=#0000FF]_x[/COLOR], [COLOR=#0000FF]this[/COLOR].[COLOR=#0000FF]_y[/COLOR][COLOR=#000000])[/COLOR], threshold, mcBitmap, [COLOR=#000000]new[/COLOR] Point[COLOR=#000000]([/COLOR]mc.[COLOR=#0000FF]_x[/COLOR], mc.[COLOR=#0000FF]_y[/COLOR][COLOR=#000000])[/COLOR], threshold[COLOR=#000000])[/COLOR][COLOR=#000000])[/COLOR] [COLOR=#000000]{[/COLOR]
[COLOR=#0000FF]return[/COLOR] [COLOR=#000000]true[/COLOR];
[COLOR=#000000]}[/COLOR]
[COLOR=#0000FF]return[/COLOR] [COLOR=#000000]false[/COLOR];
[COLOR=#000000]}[/COLOR]
[/LEFT]
[/FONT]
Thank you very much if you answer.