Based on the novel, "Do Androids Dream of Electric Sheep?" Bladerunner was the film that introduced Dick's work to people who had never previously heard of him or encountered his brand of science fiction. The story centers on Deckard (played by Harrison Ford), a policeman whose job is to track down and kill a group of renegade androids. One way in which the film differs markedly from the book is that there is an implication in the film that Deckard himself is actually an android. This possibility was never presented in the book, in fact the emotional impact of the ending is built on the fact that he is human. However, the idea of protagonists being androids or having some other identity that has been hidden from them is a common Dickian theme in many other stories. It seems that the director, Ridley Scott, may have been more interested in putting a generic Philip K Dick story on film than the particular book that he was adapting.
An interesting concept in the book that was included in the movie is a test to distinguish humans from androids. This is called a Voigt-Kampff machine (in the movie it is misspelt as Voight-Kampff), and it involves a series of questions along with sensitive measures of emotion and empathy.
A widely circulated myth about Blade Runner is that Dick hated the movie. While this is untrue, it is based on the fact that there were aspects of the movie that Dick was unhappy with. However, he did remark that the dystopian city created by Scott was "exactly as I had imagined it!" and, after discussing his disagreements with the director, publicly backed the movie.
Having conflicting opinions about an adaptation of one's work with the director of the film is probably par for the course in such a situation. Indeed it would be more surprising if there were no differences between the two men. However, the notion of Dick "hating" the movie, while untrue, is catchy and more sensational.
Perhaps it appeals to the notion of Dick as temperamental artist.