A method of generating a frame of video data comprising a pixel array from a stream of graphical objects, the method comprising: providing a pixel array corresponding to the video frame; receiving said stream of graphical objects, each graphical object having a set of parameters that define an image, said parameters including a shape (102; 202), at least one fill value (104; 204) and at least one transparency value (106; 206); processing said stream of graphical objects on an object by object basis to determine a pixel value for each pixel in said array, wherein processing said stream of graphical objects comprises: for each object: determining a first pixel value for each pixel in said array, said first pixel value being the product of said fill value and a first factor, said first factor being the product of said transparency value and an edge value, the edge value indicating the proportion of a particular pixel that is inside said shape; and blending the first pixel value for each pixel with a previous pixel value for that pixel by: multiplying the previous pixel value by a second factor, said second factor being complementary to said first factor, and summing the first pixel value and the multiplied previous pixel value. providing a pixel array corresponding to the video frame; receiving said stream of graphical objects, each graphical object having a set of parameters that define an image, said parameters including a shape (102; 202), at least one fill value (104; 204) and at least one transparency value (106; 206); processing said stream of graphical objects on an object by object basis to determine a pixel value for each pixel in said array, wherein processing said stream of graphical objects comprises: for each object: determining a first pixel value for each pixel in said array, said first pixel value being the product of said fill value and a first factor, said first factor being the product of said transparency value and an edge value, the edge value indicating the proportion of a particular pixel that is inside said shape; and blending the first pixel value for each pixel with a previous pixel value for that pixel by: multiplying the previous pixel value by a second factor, said second factor being complementary to said first factor, and summing the first pixel value and the multiplied previous pixel value. for each object: determining a first pixel value for each pixel in said array, said first pixel value being the product of said fill value and a first factor, said first factor being the product of said transparency value and an edge value, the edge value indicating the proportion of a particular pixel that is inside said shape; and blending the first pixel value for each pixel with a previous pixel value for that pixel by: multiplying the previous pixel value by a second factor, said second factor being complementary to said first factor, and summing the first pixel value and the multiplied previous pixel value. determining a first pixel value for each pixel in said array, said first pixel value being the product of said fill value and a first factor, said first factor being the product of said transparency value and an edge value, the edge value indicating the proportion of a particular pixel that is inside said shape; and blending the first pixel value for each pixel with a previous pixel value for that pixel by: multiplying the previous pixel value by a second factor, said second factor being complementary to said first factor, and summing the first pixel value and the multiplied previous pixel value. multiplying the previous pixel value by a second factor, said second factor being complementary to said first factor, and summing the first pixel value and the multiplied previous pixel value.