2D Effect library of code snippets (Shadertoy:https://www.shadertoy.com/view/ldSXzt)

colorspace.inc.glsl

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// *** COLOR TRANSFORMATION ***
//http://beesbuzz.biz/code/hsv_color_transforms.php

vec3 rgb2yiq(vec3 color){return color * mat3(0.299,0.587,0.114,0.596,-0.274,-0.321,0.211,-0.523,0.311);}
vec3 yiq2rgb(vec3 color){return color * mat3(1.,0.956,0.621,1,-0.272,-0.647,1.,-1.107,1.705);}

// Direkt HSV transzformacio 
vec3 hsvTransform(vec3 color, vec3 hsv){float  _h = hsv.x, _s = hsv.y, _v = hsv.y; float  VSU = _v*_s*cos(_h*PI/180.), VSW = _v*_s*sin(_h*PI/180.), rr = (.299*_v+.701*VSU+.168*VSW)*color.x + (.587*_v-.587*VSU+.330*VSW)*color.y + (.114*_v-.114*VSU-.497*VSW)*color.z, gg = (.299*_v-.299*VSU-.328*VSW)*color.x + (.587*_v+.413*VSU+.035*VSW)*color.y + (.114*_v-.114*VSU+.292*VSW)*color.z, bb = (.299*_v-.300*VSU+1.25*VSW)*color.x + (.587*_v-.588*VSU-1.05*VSW)*color.y + (.114*_v+.886*VSU-.203*VSW)*color.z; return vec3(rr,gg,bb); }

vec3 convertRGB4quant(vec3 color){ vec3 out0 = mod(color,1./16.); return out0;}
vec3 convertRGB4(vec3 color){return color-convertRGB4quant(color);}

vec3 convertRGB443quant(vec3 color){ vec3 out0 = mod(color,1./16.); out0.b = mod(color.b, 1./8.); return out0;}
vec3 convertRGB443(vec3 color){return color-convertRGB443quant(color);}

// Smooth HSV to RGB conversion 
vec3 hsv2rgb_smooth( in vec3 c ){vec3 rgb = clamp( abs(mod(c.x*6.0+vec3(0.0,4.0,2.0),6.0)-3.0)-1.0, 0.0, 1.0 ); rgb = rgb*rgb*(3.0-2.0*rgb); return c.z * mix( vec3(1.0), rgb, c.y);}
vec3 hsv2rgb_trigonometric( in vec3 c ){vec3 rgb = 0.5 + 0.5*cos((c.x*6.0+vec3(0.0,4.0,2.0))*3.14159/3.0);return c.z * mix( vec3(1.0), rgb, c.y);}

kaleidoscope.inc.glsl

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// *** KALEIDOSCOPE ***
vec2 kaleidoscope( vec2 uv, float n, float bias ) { 
	float angle = PI / n; float r = length( uv ); 
	float a = atan( uv.y, uv.x ) / angle; a = mix( fract( a ), 1.0 - fract( a ), mod( floor( a ), 2.0 ) ) * angle; 
	return vec2( cos( a ), sin( a ) ) * r;
}

noise.inc.glsl

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// *** PERLIN ZAJ ***
/// 2D random
vec2 random2(vec2 c) { float j = 4906.0*sin(dot(c,vec2(169.7, 5.8))); vec2 r; r.x = fract(512.0*j); j *= .125; r.y = fract(512.0*j);return r-0.5;}

/// 1D random / hash
float hash(float f){ return fract(56546.235423 * sin(f*235345.345345));}

const float F2 =  0.3660254;
const float G2 = -0.2113249;

/// simplex 2D zaj; perlin zaj egy frekvenciajahoz tartozo ertekek
float simplex2d(vec2 p){vec2 s = floor(p + (p.x+p.y)*F2),x = p - s - (s.x+s.y)*G2; float e = step(0.0, x.x-x.y); vec2 i1 = vec2(e, 1.0-e),  x1 = x - i1 - G2, x2 = x - 1.0 - 2.0*G2; vec3 w, d; w.x = dot(x, x); w.y = dot(x1, x1); w.z = dot(x2, x2); w = max(0.5 - w, 0.0); d.x = dot(random2(s + 0.0), x); d.y = dot(random2(s +  i1), x1); d.z = dot(random2(s + 1.0), x2); w *= w; w *= w; d *= w; return dot(d, vec3(70.0));}

texture.inc.glsl

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// *** 2D TEXTURA FX ***
float checker(vec2 p){ return mod(floor(p.x)+floor(p.y), 2.);}
float stripe(float p, float h){return (abs(1.-mod(p,2.)) < h) ? 1. : 0.;}
float gradient(float p){return abs(1.-mod(p,2.));}

transformation.inc.glsl

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// *** TRANSZFORMACIOK ***
vec2 sincos( float x ){return vec2(sin(x), cos(x));}
vec2 rotate2d(vec2 uv, float phi){vec2 t = sincos(phi); return vec2(uv.x*t.y-uv.y*t.x, uv.x*t.x+uv.y*t.y);}
vec3 rotate3d(vec3 p, vec3 v, float phi){ v = normalize(v); vec2 t = sincos(-phi); float s = t.x, c = t.y, x =-v.x, y =-v.y, z =-v.z; mat4 M = mat4(x*x*(1.-c)+c,x*y*(1.-c)-z*s,x*z*(1.-c)+y*s,0.,y*x*(1.-c)+z*s,y*y*(1.-c)+c,y*z*(1.-c)-x*s,0.,z*x*(1.-c)-y*s,z*y*(1.-c)+x*s,z*z*(1.-c)+c,0.,0.,0.,0.,1.);return (vec4(p,1.)*M).xyz;}

tunnel.inc.glsl

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// *** TUNNEL ***
vec3 tunnel_uvw(vec2 pos){ float u = length(pos); return vec3 (u, atan(pos.y, pos.x), 1.0/u);}
vec3 tunnel_coord(vec2 p, float frekv, float radius, mat4 mat){
    vec3 o = mat[3].xzy, d = normalize(mat[2].xyz*radius + mat[0].xyz*p.x + mat[1].xyz*p.y);
    float D=1./(d.y*d.y+d.z*d.z), a=(o.y*d.y+o.z*d.z)*D, b=(o.y*o.y+o.z*o.z-36.)*D, t=-a-sqrt(a*a-b); o+=t*d;// t = sqrt(a*a-b);
    return vec3(o.x, atan(o.y,o.z)*(frekv/PI), t);
}