RBG/YUV/HSV

const char fragmentShader_yuv420p[] =
{
"precision mediump float;\n"
"uniform sampler2D Ytex;\n"
"uniform sampler2D Utex,Vtex;\n"
"varying vec2 vTextureCoord;\n"
"void main(void) {\n"
" float nx,ny,r,g,b,y,u,v;\n"
" mediump vec4 txl,ux,vx;"
" nx=vTextureCoord[0];\n"
" ny=vTextureCoord[1];\n"
" y=texture2D(Ytex,vec2(nx,ny)).r;\n"
" u=texture2D(Utex,vec2(nx,ny)).r;\n"
" v=texture2D(Vtex,vec2(nx,ny)).r;\n"

" y=1.1643*(y-0.0625);\n"
" u=u-0.5;\n"
" v=v-0.5;\n"

" r=y+1.5958*v;\n"
" g=y-0.39173*u-0.81290*v;\n"
" b=y+2.017*u;\n"
" gl_FragColor=vec4(r,g,b,1.0);\n"
"}\n"
};

https://bbs.csdn.net/topics/390408474?list=lz

https://blog.csdn.net/qq_28299311/article/details/105101378

ec3 rgb2hsb( in 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);
}