external-image

Hi

is it possible to read the size of an external-image before to  
associate it to a port ?

I load a TIFF file by using 'read-external-image' and I use the  
function 'analize-external-image' to get the size of the image, but I  
have the next error

External image #<..> is not plain editable

Is it because I use a TIFF file or  am I using the wrong function ?

thanks for your help

Carlos Agon

P.S. I haven't problem drawing my TIFF in a window, It works fine !