in Config Variables, 
if cge_prettyhtml or cge_minhtml is set to TRUE,
html elements <picture> are removed.

I do not know if it is deliberate,
and do not find where to ask it
at  http://www.bioinformatics.org/phplabware/internal_utilities/htmLawed/

but i fix it like this :

CGExtensions/lib/htmLawed.php


#---Add the html element picture to elements:
L20 after 
'param'=>1,
add
'picture'=>1,


#---define picture as flow content 
L156 after
'object'=>1,
add
'picture'=>1,

#---define -picture as immediate parent-child for img and source :
L160 after
'option'=>array('#pcdata'=>1),
add
'picture'=>array('img'=>1, 'source'=>1),

#---allow img and source  has childs for pictures
L162 after
'object'=>array('param'=>1, 'embed'=>1),
add
'picture'=>array('source'=>1, 'img'=>1),

#---define picture as inline type for output
L166 after
'output'=>1,
add
'picture'=>1,

#---add srcset  as parameters for source
#---add sizes as parameters for source
L447
'srcset'=>array('img'=>1)
modify
'srcset'=>array('img'=>1,'source'=>1)

'sizes'=>array('link'=>1)
modify
'sizes'=>array('link'=>1,'source'=>1)

Then picture tags are not removed anymore.