A few studios have reason to be thankful this week, foremost among them Cannon Films. Cannon won't be thanking the critics for the way they've attacked the studio's "Raiders of the Lost Ark"-style adventure, "King Solomon's Mines" -- but it ought to thank moviegoers who turned the Richard Chamberlain movie into the weekend's top grosser by buying $5 million worth of tickets. If the movie beats the odds and holds its own against heavyweights like "Rocky IV," Cannon can really be thankful -- especially since the studio has already shot a sequel.

Columbia Pictures also should be pleased. Its "White Nights," the Mikhail Baryshnikov/Gregory Hines drama, was released in only 21 theaters, but it averaged nearly $23,000 per screen; that's five times the per-screen total for "King Solomon's Mines." 'Chorus' Opening Line

In Columbia's quest to hang on to business come Christmas, it will give another dancing movie a bigger opening than planned. Richard Attenborough's "A Chorus Line" -- an Embassy picture Columbia is distributing -- was originally slated to open on 475 screens in 18 cities. However, a severe shortage of holiday movies developed when studios started pulling movies from the Christmas season lineup. (Columbia, for example, delayed release of "A Fine Mess" and "Jo Jo Dancer Your Life Is Calling.") Many theater owners apparently were enthusiastic about using "Chorus Line" to plug the gap, so the studio has reportedly decided to almost double the size of the film's opening.

"A Chorus Line" will now compete with more youth-oriented films like the Steven Spielberg-produced "Young Sherlock Holmes." That's the movie, incidentally, in which Spielberg and director Barry Levinson have accomplished what seems like an impossible feat: they've made a movie about Victorian England that includes such Spielberg staples as "Gremlins"-style special effects, a Temple of Doom fully staffed with foreigners adept at grisly rituals, and a flight over moonlit rooftops. Wonder Where the Money Went

One of Christmas' chanciest commercial properties would seem to be "Santa Claus: The Movie," whose producers have repeatedly talked about its $45 million price tag. Ordinarily, a budget that big would mean the film has to make about $150 million to break even -- but in this case, the producers insist that its overseas sales already guarantee it'll break even. Of course, a few critics have already grumbled that "Santa Claus" has a low-tech look uncharacteristic of its enormous budget. Snapped The Hollywood Reporter: "The Defense Department must have been involved in the cost accounting . . ." Awards, Making Whoopi, Etc. ----

Woody Allen's "The Purple Rose of Cairo" is the best English-language film of the year, according to the London film critics, who gave out their seventh annual awards early this week. Their best director citation went to Roland Joffe' for "The Killing Fields," a 1984 film that was released in Great Britain this year. Playwright Tom Stoppard accepted for Allen . . . Actress-turned-director Penny Marshall took over the reins of the Whoopi Goldberg action comedy "Jumpin' Jack Flash" early this week, after 20th Century-Fox apparently was unhappy with the 10 days of footage shot by original director Howard Zieff. Earlier this year, Marshall was hired for "Peggy Sue Got Married" when its first director, Jonathan Demme, was replaced -- but after some unforeseen delays, she herself was replaced by Francis Coppola . . . Martin Scorsese got marginally cheerier when he made the black comedy "After Hours," and one assumes he'll lighten up even more with "The Color of Money," a Paul Newman/Tom Cruise feature he'll start filming in Chicago in January. He's making the movie for Disney . . .

Was that a promise? At the "Rocky IV" premiere, Sylvester Stallone said this is it for Rocky Balboa.