OpenGL ES 3.0 and 3DLUT

fragment_shader.glsl

// http://mahisorn.blogspot.com/2009/01/3d-lut-using-glsl.html

uniform sampler2D image;
uniform sampler3D lookup;
uniform float     imageWidth;
uniform float     imageHeight;  
varying vec2      pos; 

void main(void) {
    // find the texture coordinate corresponding to this fragment
    vec2 texCoord = vec2(pos.x/imageWidth, pos.y/imageHeight);   

    // get the corresponding color
    vec4 colorIn = texture2D(image, texCoord);

    //apply look up tables  
    vec4 colorOut;    
    colorOut.rgb = texture3D(lookup, colorIn.rgb).rgb;   

    // final color
    gl_FragColor = colorOut;  
}

init_lut3d.c

GLuint g_TexturesArray[MAX_TEXTURES];
static const int dim = 256;
GLubyte lut3D[dim][dim][dim][3];

void init_lut3D() {
    for(int i = 0; i < dim; i++) {
        for(int j = 0; j < dim; j++) {
            for(int k = 0; k < dim; k++) {
                lut3D[k][j][i][0] = k;
                lut3D[k][j][i][1] = j;
                lut3D[k][j][i][2] = i;
            }
        }
    }
}

*****************************
Create 3D texture in OpenGL
*****************************
glActiveTexture(GL_TEXTURE1);
init_lut3D();
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glGenTextures(1, &g_TexturesArray[1]);
glBindTexture(GL_TEXTURE_3D, g_TexturesArray[1]);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_T, GL_CLAMP);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_R, GL_CLAMP);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexImage3D(GL_TEXTURE_3D, 0, GL_RGB8, dim, dim, dim, 0, GL_RGB, GL_UNSIGNED_BYTE, lut3D);

multitexturing.c

// http://mahisorn.blogspot.com/2009/01/3d-lut-using-glsl.html

// Multitexturing
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, imageName);

glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_3D, lutName);

// Set Texture in Shader Program
texLoc = glGetUniformLocation(programObj, "image");
glUniform1i(texLoc, 0); //texture0
texLoc = glGetUniformLocation(programObj, "lookup");
glUniform1i(texLoc, 1); //texture1

vertex_shader.glsl

// http://mahisorn.blogspot.com/2009/01/3d-lut-using-glsl.html

varying vec2 pos;

void main(void) { 
    pos = vec2(gl_Vertex.xy);   
    gl_Position = ftransform();
}