Image forming apparatus and image forming method including preview and pre-heating features

An image forming apparatus, comprising:

• a conveyer having a sheet conveying roller configured to convey a sheet;
• an image formation engine configured to form a developing agent image on the sheet conveyed by the conveyer;
• a fixing device having a heater configured to apply heat to the sheet, the fixing device being configured to fix the developing agent image on the sheet;
• a sensor assembly configured to read an image on an original document;
• a display device configured to display an image;
• and
• a controller including hardware,
• wherein the controller is configured to perform:
• reading an image of the original document with use of the sensor assembly;
• determining whether a preview setting to display a preview image that corresponds to the read image on the display is enabled or disabled;
• when the preview setting is disabled, performing a pre-heating the heater to heat the fixing device to a temperature lower than a fixing temperature to fix the image onto the sheet;
• when the preview setting is enabled, displaying the preview image on the display without performing the pre-heating of the heater to heat the fixing device;
• raising a temperature of the fixing device so that the temperature is the fixing temperature;
• forming the developing agent image on the sheet with the image formation engine after performing the raising of the temperature to the fixing temperature;
• and
• fixing the developing agent image on the sheet with the fixing device.