Antonyms of gloomy :
light, elated, cheerful, bright, crystalline, glowing, lucid, shining, brilliant, dazzling, illumined, luminous, transparent, clear, gleaming, radiant, white, blithe, blithesome, buoyant, gay, jocund, jolly, joyful, joyous, merry, mirthful, encouraging, hopeful, optimistic, lighthearted, lightsome, cheering, cheery, comforting, cordial, festive, friendly, heartwarming, sunshiny, ecstatic, enraptured, entranced, euphoric, exhilarated, exuberant, exultant, overjoyed, rapturous, rhapsodic, jocose, jocular, jovial, excited, thrilled, rosy, sanguine, encouraged, heartened, animated, bouncing, energetic, frisky, jaunty, lively, peppy, perky, spirited, sprightful, sprightly, springy, vital, vivacious, zippy, content, gratified, pleased, satisfied, beaming, grinning, laughing, smiling, boon, carefree, careless, cavalier, devil-may-care, easygoing, happy-go-lucky, insouciant, unconcerned, blissful, buoyed, chipper, delighted, glad, gladdened, gladsome, gleeful, happy, jubilant, sunny, upbeat, ablaze, agleam, aglitter, alight, beamy, effulgent, glaring, incandescent, lambent, relucent, resplendent, sparkling, ultrabright, glossy, lustrous, shiny, floodlit, highlighted, spotlighted, moonlit, moony, starlit, sunlit, brightened, illuminated, lit, lucent.
Examples of usage:
When Lumley Ferrers left the room, his countenance was gloomy and excited rather than sad. "Ernest Maltravers, Complete", Edward Bulwer-Lytton.
He almost lifted her forward over the threshold into the cold and gloomy hall. "The Keeper of the Door", Ethel M. Dell.
John observed that he was getting a little less gloomy as he proceeded. "Fated to Be Free", Jean Ingelow.