Image reading apparatus with determination of original size, and image forming apparatus, reading method, and image forming system therewith

A reading method for an image reading apparatus,

• the image reading apparatus including:
• an original table on which an original is to be placed;
• an original presser configured to press the original placed on the original table and
• a reader configured to read the original that is irradiated with light to output image information while moving the reading position in a first direction,
• the reading method comprising:
• obtaining image information output from the reader which is at a predetermined position in the first direction, by irradiating the original with light with the original presser being in a closed state;
• determining, based on a first difference among respective image information of pixels separated from a pixel of interest by a first distance in a second direction orthogonal to the first direction, based on N differences of N pixels each surrounding the pixel of interest, and based on a second difference between a maximum image information and a minimum image information within a plurality of ranges to a pixel separated from the pixel of interest by a second distance that is larger than the first distance in the second direction, whether the pixel of interest is an edge pixel at an original end portion;
• and
• determining the size of the original based on a result of the determining.

An image forming apparatus, comprising an image forming unit configured to form an image on a predetermined recording medium based on reading data read by an image reading apparatus, wherein:

• the image reading apparatus comprising:
• an original table on which an original is to be placed;
• an original presser configured to press the original placed on the original table;
• a light source configured to irradiate the original with light;
• a reader configured to read the original that is irradiated with light by the light source to output image information while moving the reading position in a firs direction;
• and
• a controller configured to determine a size of the original based on the image information output from the reader,
• wherein the controller is configured to:
• obtain image information output from the reader which is at a predetermined position in the first direction, by turning on the light source with the original presser being in a closed state;
• determine, based on a first difference among respective image information of pixels separated from a pixel of interest by a first distance in a second direction orthogonal to the first direction, based on N first differences of N pixels each surrounding the pixel of interest, and based on a second difference between a maximum image imformation and a minimum image information within a plurality of ranges to a pixel separated from the pixel of interest by a second distance that is larger than the first distance in the second direction, whether the pixel of interest is an edge pixel at an original end portion;
• and
• determine the size of the original based on a result of the determination.

An image forming system, comprising:

• an image reading apparatus;
• and
• an image forming apparatus configured to form an image on a predetermined recording medium based on reading data read by the image reading apparatus, wherein:
• the image reading apparatus comprising:
• an original table on which an original is to be placed;
• an original presser configured to press the original placed on the original table;
• a light source configured to irradiate the original with light;
• a reader configured to read the original that is irradiated with light by the light source to output image information while moving the reading position in a first direction;
• and
• a controller configured to determine a size of the original based on the image information output from the reader,
• wherein the controller is configured to:
• obtain image information output from the reader which is at a predetermined position in the first direction, by turning on the light source with the original presser being in a closed state;
• determine, based on a first difference among respective image information of pixels separated from a pixel of interest by a first distance in a second direction orthogonal to the first direction, based on N first differences of N pixels each surrounding the pixel of interest, and based on a second difference between a maximum image information and a minimum image information o within a plurality of ranges to a pixel separated from the pixel of interest by a second distance that is larger than the first distance in the second direction, whether the pixel of interest is an edge pixel at an original end portion;
• and
• determine the size of the original based on a result of the determination.