1. A digital circuit for object identification in an image or a sequence of images, each image comprising an array of pixels; the circuit comprising a plurality of synchronously-operating like pixel processing elements, one for each pixel in the pixel array of an image, each pixel processing element comprising a pixel value register receiving a value for that pixel, a neighbour value register, and a processor connected with said pixel value register and said a neighbour value register, the processor being adapted to receive adjacent pixel values and adjacent neighbour values for at least two adjacent pixels in that one image or in either of the images respectively preceding and succeeding that one image in the sequence of images, the processor being adapted in a series of iterations to replace the value in the neighbour value register with a function of: the current value in the neighbour value register; the adjacent pixel value from an adjacent pixel whose pixel value is different from the current value of the pixel value register or the adjacent neighbour value from an adjacent pixel whose pixel value is the same as the current value of the pixel value register.