Circle Warp.fs

Code

uniform sampler2D inputImage;
uniform float radius;
uniform float width;
uniform float resultRotation;
precision mediump float;
/*{
    "CATEGORIES": [
        "Distortion Effect"
    ],
    "CREDIT": "VIDVOX",
    "DESCRIPTION": "Warps an image to fit in a circle by fitting the height of the image to the height of a circle",
    "INPUTS": [
        {
            "NAME": "inputImage",
            "TYPE": "image"
        },
        {
            "DEFAULT": 0.5,
            "MAX": 0.5,
            "MIN": 0,
            "NAME": "radius",
            "TYPE": "float"
        },
        {
            "DEFAULT": 1,
            "MAX": 2,
            "MIN": 0,
            "NAME": "width",
            "TYPE": "float"
        },
        {
            "DEFAULT": 0,
            "MAX": 1,
            "MIN": 0,
            "NAME": "resultRotation",
            "TYPE": "float"
        }
    ],
    "ISFVSN": "2"
}
*/


const float pi = 3.1415926535897932384626433832795;

vec2 rotatePointNorm(vec2 pt, float rot)	{
	vec2 returnMe = pt;

	float r = distance(vec2(0.50), returnMe);
	float a = atan((returnMe.y-0.5),(returnMe.x-0.5));

	returnMe.x = r * cos(a + 2.0 * pi * rot - pi) + 0.5;
	returnMe.y = r * sin(a + 2.0 * pi * rot - pi) + 0.5;
	
	returnMe = returnMe;
	
	return returnMe;
}

void main()	{
	vec4		inputPixelColor;
	vec2		pt = (gl_FragCoord.xy / u_resolution.xy);
	vec2		ct = vec2(0.5,0.5);
	
	pt -= ct;
	pt.x /= width;
	pt += ct;
	
	pt = mix(vec2((pt.x*u_resolution.x/u_resolution.y)-(u_resolution.x*.5-u_resolution.y*.5)/u_resolution.y,pt.y), 
				vec2(pt.x,pt.y*(u_resolution.y/u_resolution.x)-(u_resolution.y*.5-u_resolution.x*.5)/u_resolution.x), 
				step(u_resolution.x,u_resolution.y));
	pt = rotatePointNorm(pt,resultRotation+0.5);
	if (distance(pt,ct) < radius)	{
		float		a = (atan(ct.y-pt.y,ct.x-pt.x) + pi) / (2.0*pi);
		//inputPixelColor = texture2D(inputImage, pt);
		pt.y -= 0.5;
		pt.y /= 2.0*sqrt(pow(radius,2.0)-pow((pt.x-0.5),2.0));
		pt.y += 0.5;
		inputPixelColor = texture2D(inputImage, pt);
	}
	
	gl_FragColor = inputPixelColor;
}