Printing apparatus and method of controlling the same that selectively perform predetermined image processing based on a detected sheet size

A printing apparatus comprising:

• a conveyance unit that includes a feeding roller and a registration roller that convey a sheet;
• a detection unit including a registration sensor that detects a size in a sheet conveying direction of a first sheet that is being conveyed by the conveyance unit;
• a printer engine that prints an image on the sheet conveyed by the conveyance unit;
• an image processor including an application-specific integrated circuit and software that execute image processing on image data to be printed by the printer engine;
• a memory that stores a set of instructions;
• and
• a processor that executes instructions, of the set of instructions:
• (a) to confirm whether the detection unit has detected the size of the first sheet;
• (b) to cause the conveyance unit to convey the first sheet to print an image on the first sheet by the printer engine in a free size printing mode in which the printing apparatus does not accept a designation of a size of sheets to be used for printing by the printer engine from a user, before a user instruction for starting printing is accepted;
• (c) to cause, in the free size printing mode, the conveyance unit to start conveying a portion of sheets of a plurality of sheets following the first sheet to print, by the printer engine, a portion of images on the portion of the sheets following the first sheet, before the detection unit detects the size of the first sheet;
• (d) to cause, in the free size printing mode, the conveyance unit to start conveying other sheets, of the plurality of sheets, following the portion of the sheets following the first sheet, to print other images on the other sheets, in accordance with having confirmed that the detection unit detects the size of the first sheet;
• (e) to cause, in the free size printing mode, the image processor to perform a predetermined image processing using a predetermined size in the sheet conveying direction, on image data of the portion of the images to be printed on the portion of the sheets following the first sheet, before the detection unit detects the size of the first sheet;
• (f) to cause, in the free size printing mode, the image processor to perform the predetermined image processing, using the size detected by the detection unit, on image data of the other images to be printed on the other sheets in accordance with having confirmed that the detection unit detects the size of the first sheet;
• and
• (g) to cause the printer engine to print the portion of the images, on the portion of sheets following the first sheet, based on image data on which the predetermined image processing using the predetermined size has been performed, and to print the other images on the other sheets based on the image data on which the predetermined image processing using the detected size has been performed,
• wherein the printing of the portion of the images and the printing of the other images in (g) starts after the conveyance of the portion of sheets following the first sheet in (c) or the conveyance of the other sheets in (d) has been started and the predetermined image processing in (e) or (f) has been completed.