Graphics as Input

An image is equivalent to its symbolic expression. You can operate on an image as you would on 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
Type a Wolfram Language Replace command after the output graphic and evaluate.
In[4]:=
Click for copyable input
The disks are now replaced by squares.
Out[5]=