How can I find brick part number from a picture? I found some books I like, but the book only give pictures of the parts. For example, this one



How can I know the part number (for example in bricklink) from the picture?
You'll need to start learning the nomenclature for those pieces.
For example the long straight pieces you have there with holes on top are &quot;Technic, Brick 1 x 12 with Holes&quot;
The pieces with rounded ends are lift arms. You can browse through the list of them here or take a stab at their descriptions using the width and number of pin holes. For example the purple on you have there is

1 hole wide

9 holes long

as think as a normal LEGO brick (some are half that thickness)

Bent with 6 on one line and 4 on the other
so &quot;Technic, Liftarm 1 x 9 Bent (6 - 4) Thick&quot;