1. An image generating method for acquiring a plurality of frames of data from video data having a multitude of frames of data, the data representing tones of an image by means of a multitude of pixels, and synthesizing the plurality of frames of data to generate image data for representing by means of multitude of pixels the tones of an output image for an image output device, the method comprising the steps of: (a) determining, on the basis of image quality setting data that allows setting of image quality of the output image, a number of frames of data for acquisition from the video data, and acquiring the determined number of frames of data from the video data; and (b) synthesizing the acquired number of frames of data and generating the image data.