« Get first non transparent pixel in a bitmap, 3 approaches and benchmarks
Get first non transparent pixel in a bitmap Part III »

Get first non transparent pixel in a bitmap update

On the way home I realized I had made a mistake in my previous blog post. In my hitTest() version, for some reason I had used a Rectangle which was the full size of the target bitmap. Like the FloodFill version, this "hit test" rectangle only needs to be one pixel in height. This means a lot less checking.

Behold the updated version:

PLAIN TEXT
Actionscript:
  1. public static function getFirstNonTransparentPixelHitTest(bmd:flash.display.BitmapData,test_fill_color:uint=0xFFFFFF00):Point{
  2.     var hit_rect:Rectangle=new Rectangle(0,0,bmd.width,1);
  3.     for(var i:uint=0;i<bmd.height;i++){
  4.         if(bmd.hitTest(new Point(),0x01,hit_rect)){
  5.             var hit_bmd:BitmapData=new BitmapData(bmd.width,1,true,0);
  6.             var m:Matrix=new Matrix(1,0,0,1,0,-i);
  7.             hit_bmd.draw(bmd,m);
  8.             hit_bmd.floodFill(0,0,test_fill_color);//use yellow, assume that the image tested is monochrome... (black and transparent)
  9.             var bounds:Rectangle=hit_bmd.getColorBoundsRect(0xFFFFFFFF,test_fill_color);
  10.             return new Point(bounds.width,i);
  11.         }
  12.         hit_rect.y++;
  13.     }
  14.     return null;
  15. }

Now behold the new results:

Test with image w:100,h:100
testFirstBitmapHitTest() first:(x=30, y=30)
testFirstBitmapHitTest() test took : 2 milliseconds
testFirstBitmapLooping() first:(x=30, y=30)
testFirstBitmapLooping() test took : 1 milliseconds
testFirstBitmapFloodFill() first:(x=30, y=30)
testFirstBitmapFloodFill() test took : 3 milliseconds

Test with image w:500,h:500
testFirstBitmapHitTest() first:(x=150, y=150)
testFirstBitmapHitTest() test took : 8 milliseconds
testFirstBitmapLooping() first:(x=150, y=150)
testFirstBitmapLooping() test took : 32 milliseconds
testFirstBitmapFloodFill() first:(x=150, y=150)
testFirstBitmapFloodFill() test took : 20 milliseconds

Test with image w:1000,h:1000
testFirstBitmapHitTest() first:(x=300, y=300)
testFirstBitmapHitTest() test took : 13 milliseconds
testFirstBitmapLooping() first:(x=300, y=300)
testFirstBitmapLooping() test took : 117 milliseconds
testFirstBitmapFloodFill() first:(x=300, y=300)
testFirstBitmapFloodFill() test took : 42 milliseconds

Test with image w:2000,h:2000
testFirstBitmapHitTest() first:(x=600, y=600)
testFirstBitmapHitTest() test took : 23 milliseconds
testFirstBitmapLooping() first:(x=600, y=600)
testFirstBitmapLooping() test took : 282 milliseconds
testFirstBitmapFloodFill() first:(x=600, y=600)
testFirstBitmapFloodFill() test took : 102 milliseconds

So the hitTest approach wins after all :)

***EDIT :

AND CLICK HERE TO READ UPDATE!

***

Tags:

This entry was posted on Tuesday, February 10th, 2009 at 8:24 pm and is filed under AS3, Flash, experiment. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

Leave a Reply