1. An image processing system comprising: a bus for transmitting image data; means for generating a first form of image data representing a frame of an original image; first and second processing means, connected to said bus, for receiving and processing image data transmitted on said bus, said first processing means adapted to process said first form of the image data, and said second processing means being adapted to process a second form of the image data, said second form being different from said first form; converting means, connected to said generating means, for converting said first form of image data generated by said generating means into the second form of image data representing a frame of the original image; storage means, connected to said converting means, for storing said second form of image data output from said converting means; and transmitting means, connected to said bus, said generating means and said storage means, for intermittently transmitting a frame of said first form of image data generated by said generating means on a basis of a predetermined amount through said bus to said first processing means, while transmitting said second form of image data stored in said storage means through said bus to said second processing means in blank intervals which occur between the intermittent transmissions of a frame of said first form of image data.