1. A method of processing a stereoscopic image to be displayed on a target screen, wherein a disparity information is associated with said stereoscopic image and is adapted for the display of the stereoscopic image on an original screen, a size of the original screen being different from a size of the target screen, a format of the original screen being different from a format of the target screen, the stereoscopic image comprising a first image and a second image, the method comprising: selecting a part of said first image according to at least one property associated with the first image and according to the size and the format of the target screen, calculating a disparity budget associated with the target screen according to the original disparity information associated with the selected part of the first image, a lower limit of said disparity budget being equal to the opposite of the product of a value representative of an interocular distance, of a value representative of a viewing distance of a content displayed on the target screen and of a value representative of an admissible value of the vergence accommodation conflict, and an upper limit of said disparity budget being equal to the smallest value between the absolute value of said lower limit and the value representative of the interocular distance, calculating a target disparity information associated with the selected part of the first image according to said disparity budget and original disparity information associated with the selected part of the first image, and displaying said selected part of the first image and corresponding part of said second image according to said target disparity information.