Abstract: An embodiment of the present invention provides a printer configured to print on a print medium. The printer includes a thermal head and a control unit. The thermal head has a plurality of heating elements that are arranged in a line. The control unit is configured to control thermal energy to be applied to the plurality of heating elements, in accordance with information based on image data. The information includes whether to apply a pulse of energizing current in each of a plurality of periods being preset during a scanning line time for one line. The plurality of periods is set in an order from a long period to a short period during the scanning line time.

Abstract: A printer is configured to print on a print medium having a thermal color developing layer and includes: a thermal head having a plurality of heating elements that are arranged in a line; and a processor configured to: set a first application period of a pulse of energizing current, during a scanning line time for one line, the pulse of energizing current applying thermal energy that causes the thermal color developing layer to develop color, to the plurality of heating elements, correct a length of the first application period, which is set by the processor, based on an image to be printed, and determine print speed to be applied in printing the whole image at a constant speed, by extending the scanning line time so as to contain a maximum length of the first application period that has been corrected by the processor.