Ok i forgot many things..... sorry
(( <blends-background>true</blends-background> - this makes the effect preview in the editor.))
If the fx is almost here for you ?
"current" is declared so try this;
color.rgb = texture2D(samplerFront, vec2(current, uv.y)).rgb;
instead this : color.rgb = texture2D(samplerFront, vec2(float (((color.r + color.g + color.b) / 3.0)*1.0), 0.5)).rgb;
Mix is missing but try any way, i can add mix later with intensity...
Btw; I think this fx is not same c-dex fx.. i must meditate.. <img src="{SMILIES_PATH}/icon_e_smile.gif" alt=":)" title="Smile">
With mix it become : color.rgb = mix(color.rgb,texture2D(samplerFront, vec2(uv.x, uv.y)).rgb*current,intensity);
http://gigatron3k.free.fr/html5/C2/FX/cmixer