Simplify command

tools/2d_auto_threshold/auto_threshold.xml

@@ -23,9 +23,7 @@
     '$th_method.method_id'
     '$th_method.block_size'
     '$th_method.threshold'
-    #if $invert_output:
-        --invert_output
-    #end if
+    $invert_output
     ]]>
     </command>
     <inputs>
@@ -74,7 +72,7 @@
                 <param name="block_size" type="integer" value="5" label="Odd size of pixel neighborhood for determining the threshold" />
             </when>
         </conditional>
-        <param name="invert_output" type="boolean" checked="false" truevalue="True" falsevalue="False" label="Invert output labels" help="Pixels are usually assigned the label 0 if the pixel value is below (or equal to) the threshold, and 255 if it is above the threshold. If this option is activated, pixels are assigned the label 255 if the pixel value is below (or equal to) the threshold, and 0 if it is above the threshold." />
+        <param name="invert_output" type="boolean" checked="false" truevalue="--invert_output" falsevalue="" label="Invert output labels" help="Pixels are usually assigned the label 0 if the pixel value is below (or equal to) the threshold, and 255 if it is above the threshold. If this option is activated, pixels are assigned the label 255 if the pixel value is below (or equal to) the threshold, and 0 if it is above the threshold." />
     </inputs>
     <outputs>
        <data format="tiff" name="output" from_work_dir="out.tif" />