I don’t have any answers (yet) from from previous question on GDAL memory raster + OpenLayers, so i’ll try to ask an easier question 
Anyone knows how to access GDAL memory with command lines when using the -of MEM output ? As ex, after this command :
gdaldem color-relief -of MEM -alpha C:tmpmyImg.tiff C:tmpmyLgd.txt myMemOuput