Abstract: For every point of an image in a special effects digital optical image formation method and apparatus the value of a border key signal is obtained by conducting a search for the maximum value of the subject's key signal in an analysis window centered on this point. The subject's key signals of the points in the window are delayed so as to make them simultaneous and are supplied to the same comparator which may be controlled in order to inhibit some of its inputs so as to define, for example, a circular analysis window; such a process makes it possible to obtain a regular border.

Abstract: The method for the inlaying of color video images consists on the one hand in generating a switching signal, or dividing key, applying a gain on the image points belonging to the contour of the subject to be inlaid, in proportion to the distance value (DIST) between the color of the point and that of the back-ground, and on the other hand in carrying out a mixing of the source image and a new background image which is a function of the value of the dividing key signal at the point in question and such that the values of the source signal and of the new background signal are fixed at constants over the width of the contour.

Abstract: The obtaining of a geometrical effect, with an image, is done by a two-dimensional filter with variable characteristics controlled by a computer to compute the points of a pre-established conversion grid, superimposed on the image, as a function of neighboring points of the original image and of the desired effect. A memory contains the original image. Auxiliary images, obtained by successive reductions, in fixed proportion, of the original image, are stored and a point of the conversion grid is computed by selecting that of the memories for which the reduction factor enables the easiest computation while, at the same time, preserving the quality of the image.

Abstract: A programmable circuit is provided for the series-parallel transformation of a digital signal and application thereof to a digital video signal receiver, comprising a circuit for detecting the synchronizing words in the series digital signal, a phase comparator generating pulses I and I characteristic of the coincidences and non coincidences between the parallel clock signal generated by a programmable divider from the series clock signal and pulses characteristic of the times when synchronizing words are detected; a logic circuit receives the pulses from the phase comparator and transfers them to the sync control input of a programmable divider when a predetermined programmable number of successive non coincidences or coincidences has been detected. This logic circuit also has a disconnecting control input. This circuit is implanted in a prediffused integrated network.