<fxlayout>
  <page name="Adjust Levels">
<separator label="RGB"/>
    <control>in_rgb</control>
    <control>out_rgb</control>
<separator label="Red"/>
    <control>in_r</control>
    <control>out_r</control>
<separator label="Green"/>
    <control>in_g</control>
    <control>out_g</control>
<separator label="Blue"/>
    <control>in_b</control>
    <control>out_b</control>
<separator label="Alpha"/>
    <control>in_m</control>
    <control>out_m</control>
  </page>
  <page name="Gamma">
    <histogram/>
    <control>gamma_rgb</control>
    <control>gamma_r</control>
    <control>gamma_g</control>
    <control>gamma_b</control>
    <control>gamma_m</control>
  </page>
 
</fxlayout>