Abstract: Special effects are produced on video images by means of a method of geometrical transformation which can involve a translation, a rotation, an affine transformation or an effect of perspective. The method consists:in locating each point of the initial image by means of coordinates (X, Y, O) in a cartesian reference frame designated as a movable reference frame and related to the initial image;in representing each point of the initial image by a binary word;in storing the initial image in a storage device having two read address inputs and one data output, the function of the device being to deliver a binary word corresponding to the point with coordinates (X, Y, O) in the initial image when read address values X and Y are applied respectively to the two inputs:in causing each point of the transformed image resulting from an initial-image transformation to be located by means of coordinates (X.sub.3, Y.sub.

Abstract: A generator for generating shapes derived from a square comprises a memory for storing the values of the function .vertline.X.vertline. and a memory for storing the values of the function .vertline.Y.vertline., an adder for delivering a value M=.vertline.X.vertline.+.vertline.Y.vertline., and a memory for delivering control signals to a video switcher as a function of the value of M. In the case of points located inside a square corresponding to the equation .vertline.X.vertline.+.vertline.Y.vertline.=K, the value of M is smaller than K. The address values X and Y are computed as a function of the coordinates of the point considered in the image to be generated and as a function of the geometrical transformations to be made in the figure in order to vary its shape and its position.

Abstract: The method consists in computing a luminance and/or chrominance gradient indicator (I.sub.g) at each point of the image, in computing a threshold value (S(X.sub.o)) as a function of each gradient obtained, in measuring the inter-image luminance and/or chrominance difference of each point of the image, in comparing the inter-image difference obtained at each point with the corresponding computed threshold value, in applying the result of the comparison to the input of a density-filtering device in order to detect the density of moving points in proximity to each scanned point and to compare the density obtained in respect of each point with a predetermined density threshold value in order to provide an indication of moving points when the density at each point considered exceeds the predetermined density threshold value.