Flambe - Alpha Hit Test

gistfile1.hx

// Checks if a point on a texture hits a pixel with 0 alpha
// @th3d0g


// ImageUtils.hx
import flambe.display.Texture;
import haxe.io.Bytes;
import haxe.io.BytesData;

class ImageUtils
{
  public static function hitTestAlpha( x:Float, y:Float, texture:Texture ):Bool {

    var bytes:Bytes = texture.readPixels( Math.round( x ), Math.round( y ), 1, 1 );
    var bytesData:BytesData = bytes.getData();
    
    var colourHex:String = bytes.toHex();
    var colourInt:Int = Std.parseInt( "0x" + colourHex );
    var hasHitAlpha:Bool = ( colourInt >> 24 == 0 );
    
    return hasHitAlpha;
  }
}

// Example
imageSprite.pointerDown.connect(function(event : PointerEvent){
  var imageSprite:ImageSprite = cast( event.hit, ImageSprite );
  var hasHitAlpha = ImageUtils.hitTestAlpha(  event.viewX - imageSprite.x._, 
                                                event.viewY - imageSprite.y._, 
                                                imageSprite.texture             );

  trace( hasHitAlpha );
});

Needs some optimisation.