r_e_c_u_r/Shaders/1-input/hsv_control.frag

//1-input
#ifdef GL_ES
precision mediump float;
#endif

varying vec2 v_texcoord;
uniform sampler2D u_tex0;
uniform sampler2D u_tex1;
uniform vec2 u_resolution;
uniform float u_time;
uniform float u_x0;
uniform float u_x1;
uniform float u_x2;
uniform float u_x3;

vec3 rgb2grayscale(vec3 c)
{
    return(vec3(dot(c, vec3(0.299, 0.587, 0.114))));
}

vec3 rgb2hsv(vec3 c)
{
    vec4 K = vec4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
    vec4 p = mix(vec4(c.bg, K.wz), vec4(c.gb, K.xy), step(c.b, c.g));
    vec4 q = mix(vec4(p.xyw, c.r), vec4(c.r, p.yzx), step(p.x, c.r));

    float d = q.x - min(q.w, q.y);
    float e = 1.0e-10;
    return vec3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);
}

vec3 hsv2rgb(vec3 c)
{
    vec4 K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
    vec3 p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www);
    return c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);
}

void main(){

vec2 pos = v_texcoord;
vec4 color = texture2D(u_tex0, pos);

vec3 hsv = rgb2hsv(color.rgb);
hsv.x += u_x0 - 0.5;
hsv.y += u_x1 - 0.5;
hsv.z += u_x2 - 0.5;
//hsv.x += -0.2;
vec3 rgb = hsv2rgb(hsv.xyz);


gl_FragColor = vec4(rgb, color.a);

}