A data-generating device for generating movie data from a still image comprising: a system control means arranged to determine a frame rate of the movie data to be generated; determine a number of frames, FN, according to said frame rate; determine a masking factor based on the said number of frames, and calculate a number of maskings, MN, by multiplying a total number of pixels of the still image with the masking factor, wherein the masking factor corresponds to the rate of the number of pixels to be masked with respect to the total number of pixels of the still image and wherein when said number of frames, FN, is greater, the masking factor is set higher; copy the still image FN-times to generate FN copy images; mask MN pixels in each copy, wherein for each of the MN pixels, a masking color of a coordinate of the pixel is determined as an intermediate color between a color of the pixel to be masked and a color of the pixels around the pixel to be masked, the pixel is masked using the masking color, and at least part of coordinates of the pixels to be masked are different between each copy (S9-S15), generate movie data by combining the FN copy images, wherein the system control means is arranged to divide each frame of said FN copy images in a plurality of regions and vary the masking factor in at least one of the regions of one frame from the masking factor in other regions of the same frame. a system control means arranged to determine a frame rate of the movie data to be generated; determine a number of frames, FN, according to said frame rate; determine a masking factor based on the said number of frames, and calculate a number of maskings, MN, by multiplying a total number of pixels of the still image with the masking factor, wherein the masking factor corresponds to the rate of the number of pixels to be masked with respect to the total number of pixels of the still image and wherein when said number of frames, FN, is greater, the masking factor is set higher; copy the still image FN-times to generate FN copy images; mask MN pixels in each copy, wherein for each of the MN pixels, a masking color of a coordinate of the pixel is determined as an intermediate color between a color of the pixel to be masked and a color of the pixels around the pixel to be masked, the pixel is masked using the masking color, and at least part of coordinates of the pixels to be masked are different between each copy (S9-S15), generate movie data by combining the FN copy images, wherein determine a frame rate of the movie data to be generated; determine a number of frames, FN, according to said frame rate; determine a masking factor based on the said number of frames, and calculate a number of maskings, MN, by multiplying a total number of pixels of the still image with the masking factor, wherein the masking factor corresponds to the rate of the number of pixels to be masked with respect to the total number of pixels of the still image and wherein when said number of frames, FN, is greater, the masking factor is set higher; copy the still image FN-times to generate FN copy images; mask MN pixels in each copy, wherein for each of the MN pixels, a masking color of a coordinate of the pixel is determined as an intermediate color between a color of the pixel to be masked and a color of the pixels around the pixel to be masked, the pixel is masked using the masking color, and at least part of coordinates of the pixels to be masked are different between each copy (S9-S15), for each of the MN pixels, a masking color of a coordinate of the pixel is determined as an intermediate color between a color of the pixel to be masked and a color of the pixels around the pixel to be masked, the pixel is masked using the masking color, and at least part of coordinates of the pixels to be masked are different between each copy (S9-S15), generate movie data by combining the FN copy images, wherein the system control means is arranged to divide each frame of said FN copy images in a plurality of regions and vary the masking factor in at least one of the regions of one frame from the masking factor in other regions of the same frame.