Whether it's true or not, "Joker" feels like it was commissioned specifically as a tie-in to the biggest movie of the year. It's not an adaptation of "The Dark Knight," nor is it exactly a spin-off, but it's informed by that movie, even though -- given the lead time on projects like this -- it must have been written long before Azzarello saw the film in theaters. Yet there's a clear Heath Ledger influence here, and it seems as if Azzarello and Bermejo were working off early teaser trailer indications of the film, and then extrapolating from there. Their version of the Joker isn't the same as what we see in the movie, but it's certainly on the Ledger end of the spectrum. And I think that's a respectable choice, considering that Ledger has defined the character for our generation.
I'm getting angry e-mails demanding that I "check [my] facts" and telling me all about Bermejo developing the Joker look back in 2005. I understand all of that. Which is exactly why I included key words like "whether it's true or not," "feels," and "seems." I know they couldn't have seen the movie before they produced the graphic novel, and I even include the sentence saying, "it must have been written long before Azzarello saw the film in theaters."
So, please, relax. I didn't get any facts wrong. But I may have been a bit unclear.
Ledger's portrayal still informs the Joker of the graphic novel whether or not the creators saw his performance at any time during the project's development. His performance is the definitive Joker for this era, and with the Ichi the Killer look of both Ledger and the Bermejo version, it's impossible to separate them at this point. This graphic novel "feels" and "seems" related to the film version. That doesn't mean it was intended to be.