This is documentation for Mathematica 6, which was
based on an earlier version of the Wolfram Language.
View current documentation (Version 11.1)

Graphics As Input

An image is equivalent to its symbolic expression. You can operate on an image as you would a symbolic expression.
This input produces some disks.
In[1]:=
Click for copyable input
Out[1]=
Type // InputForm after the graphic to get the symbolic expression that corresponds to the graphic.
In[2]:=
Click for copyable input
In[3]:=
Click for copyable input
Out[3]//InputForm=
Type a Mathematica Replace command after the output graphic and evaluate.
In[4]:=
Click for copyable input
The disks are now replaced by squares.
Out[5]=