/*{
	"CREDIT": "by VIDVOX",
	"CATEGORIES": [
		"Stylize"
	],
	"INPUTS": [
		{
			"NAME": "inputImage",
			"TYPE": "image"
		},
		{
			"NAME": "intensity",
			"TYPE": "float",
			"MIN": 0.0,
			"MAX": 50.0,
			"DEFAULT": 50.0
		},
		{
			"NAME": "threshold",
			"TYPE": "float",
			"MIN": 0.0,
			"MAX": 1.0,
			"DEFAULT": 0.5
		},
		{
			"NAME": "sobel",
			"TYPE": "bool",
			"DEFAULT": 1.0
		},
		{
			"NAME": "opaque",
			"TYPE": "bool",
			"DEFAULT": true
		}
	]
}*/


varying vec2 left_coord;
varying vec2 right_coord;
varying vec2 above_coord;
varying vec2 below_coord;

varying vec2 lefta_coord;
varying vec2 righta_coord;
varying vec2 leftb_coord;
varying vec2 rightb_coord;

float gray(vec4 n)
{
	return (n.r + n.g + n.b)/3.0;
}

void main()
{

	vec4 color = IMG_THIS_PIXEL(inputImage);
	vec4 colorL = IMG_NORM_PIXEL(inputImage, left_coord);
	vec4 colorR = IMG_NORM_PIXEL(inputImage, right_coord);
	vec4 colorA = IMG_NORM_PIXEL(inputImage, above_coord);
	vec4 colorB = IMG_NORM_PIXEL(inputImage, below_coord);

	vec4 colorLA = IMG_NORM_PIXEL(inputImage, lefta_coord);
	vec4 colorRA = IMG_NORM_PIXEL(inputImage, righta_coord);
	vec4 colorLB = IMG_NORM_PIXEL(inputImage, leftb_coord);
	vec4 colorRB = IMG_NORM_PIXEL(inputImage, rightb_coord);

	float gx = (0.0);
	float gy = (0.0);
	if (sobel)	{
		gx = (-1.0 * gray(colorLA)) + (-2.0 * gray(colorL)) + (-1.0 * gray(colorLB)) + (1.0 * gray(colorRA)) + (2.0 * gray(colorR)) + (1.0 * gray(colorRB));
		gy = (1.0 * gray(colorLA)) + (2.0 * gray(colorA)) + (1.0 * gray(colorRA)) + (-1.0 * gray(colorRB)) + (-2.0 * gray(colorB)) + (-1.0 * gray(colorLB));
	}
	else	{
		gx = (-1.0 * gray(colorLA)) + (-1.0 * gray(colorL)) + (-1.0 * gray(colorLB)) + (1.0 * gray(colorRA)) + (1.0 * gray(colorR)) + (1.0 * gray(colorRB));
		gy = (1.0 * gray(colorLA)) + (1.0 * gray(colorA)) + (1.0 * gray(colorRA)) + (-1.0 * gray(colorRB)) + (-1.0 * gray(colorB)) + (-1.0 * gray(colorLB));
	}

	float bright = pow(gx*gx + gy*gy,0.5);
	vec4 final = color * bright;

	//	if the brightness is below the threshold draw black
	if (bright < threshold)	{
		if (opaque)
			final = vec4(0.0, 0.0, 0.0, 1.0);
		else
			final = vec4(0.0, 0.0, 0.0, 0.0);
	}
	else	{
		final = final * intensity;
		if (opaque)
			final.a = 1.0;
	}

	gl_FragColor = final;
}