var TO_RADIANS = Math.PI / 180; 

function ImageParticle(img, posx, posy)
{

	// the position of the particle
	this.posX = posx; 
	this.posY = posy; 
	// the velocity 
	this.velX = 0; 
	this.velY = 0; 
	
	// multiply the particle size by this every frame
	this.shrink = 1; 
	this.size = 1; 
	// if maxSize is a positive value, limit the size of 
	// the particle (this is for growing particles).
	this.maxSize = -1;
	
	// multiply the velocity by this every frame to create
	// drag. A number between 0 and 1, closer to one is 
	// more slippery, closer to 0 is more sticky. values
	// below 0.6 are pretty much stuck :) 
	this.drag = .75; 
	
	// add this to the yVel every frame to simulate gravity
	this.gravity = 0.5; 
	
	// current transparency of the image
	this.alpha = 1; 
	// subtracted from the alpha every frame to make it fade out
	this.fade = 0; 

	// the amount to rotate every frame
	this.spin = 0; 
	// the current rotation
	this.rotation = 0; 
	
	// the blendmode of the image render. 'source-over' is the default
	// 'lighter' is for additive blending.
	this.compositeOperation = 'source-over';

	// the image to use for the particle. 
	this.img = img; 

	this.update = function() 
	{
	
		// simulate drag
		this.velX *= this.drag; 
		this.velY *= this.drag;
		
		// add gravity force to the y velocity 
		this.velY += this.gravity; 
		
		// and the velocity to the position
		this.posX += this.velX;
		this.posY += this.velY; 
		
		// shrink the particle
		this.size *= this.shrink;
		// if maxSize is set and we're bigger, resize!
		if((this.maxSize>0) && (this.size>this.maxSize))
			this.size = this.maxSize; 
		
		// and fade it out
		this.alpha -= this.fade; 	
		if(this.alpha<0) this.alpha = 0; 
		
		// rotate the particle by the spin amount. 
		this.rotation += this.spin; 
		
	 
	}
	
	this.render = function(c)
	{
	
		// if we're fully transparent, no need to render!
		if(this.alpha ==0) return;
		
		// save the current canvas state
		c.save(); 
		
		// move to where the particle should be
		c.translate(this.posX, this.posY);
		
		// scale it dependent on the size of the particle
		c.scale(this.size,this.size);
		
		// and rotate
		c.rotate(this.rotation * TO_RADIANS);
						
		// move the draw position to the center of the image
		c.translate(img.width*-0.5, img.width*-0.5);
		
		// set the alpha to the particle's alpha
		c.globalAlpha = this.alpha; 
		
		// set the composition mode
		c.globalCompositeOperation = this.compositeOperation;
				
		// and draw it! 
		c.drawImage(img,0,0);
		
		// and restore the canvas state
		c.restore();
					
	}


}


function randomRange(min, max)
{
	return ((Math.random()*(max-min)) + min); 
}