PURPOSE: To decide whether the respective minimum recording elements of a picture recording device are picture-recorded or not based on a gradation value obtained from an original so as to obtain a dot picture.

CONSTITUTION: A matrix D where thresholds are set to be elements and one element among them is set to be a reference element is prepared in a size including dot blocks 5 arranged in a prescribed are pitch in a direction where they are inclinced at a prescribed angle against an orthogonal coordinate system based on the recording direction of a recording device. A point in the same dot block as a recording element A is obtained among reference points having a relatively constant position relation in the respective dot blocks. A matrix element where the relative position relation between the relative position relation of the recording element A and the reference element of the matrix D against the recording element where a value obtained by making the coordinate into an integer is set to be a coordinate is selected. It is set as the threshold and it is compared with the gradation value allocated to the recording element A and a recording signal is generated. Thus, the dot picture having the arbitrary screen angle screen pitch and having the desired form and size, which correspond to the gradation value, can be obtained.