Diff images using external diff tool with P4Merge

Description

Hi, I'm using:

• SourceTree 2.1.2.5 on 64-bit Windows 10
• Git 2.13.2
• P4Merge
  and I have configured P4Merge as the external diff/merge tool.

I have 2 branches:

• master - commit 09f5e69
  This commit has pushed this picture (pic1).
• master - commit 09f5e69
  This commit has pushed this picture (pic2).

Since P4Merge can diff pictures, I want to diff those 2 commits with P4Merge. If I click that action, P4Merge returns an error.

Questions

I want to diff 2 commits to compare text codes or pictures.
Do I have to add "Diff commands" or parameters to diff those 2 commits?
Or is this feature impossible?

-Best Regards