Image reading apparatus
AssigneeCanon Kabushiki Kaisha
InventorsYoichiro Makino, Koji Kobayashi, Nobuyuki Bannai
Life of this patent
Estimating the term…
Abstract
A method is provided for processing image data read from a book document placed on a platen of an image reading apparatus. The method includes determining a background pixel of the image data based on a luminance difference or a color difference between neighboring pixel arrays, identifying a shadow region based on a luminance change between the neighboring background pixel arrays, discriminatively detecting a shadow of a binding portion and a shadow of a front edge in a document region with reference to a changing direction of shadow luminance, and performing a luminance correction on the shadow region according to characteristics of the shadows.
Claims17
A method for processing image data read from a book document placed on a platen, the method comprising:
- determining a target pixel of the image data as a background pixel when a difference between the target pixel and a neighboring pixel is less than a threshold, the neighboring pixel being in a first direction perpendicular to a binding portion of the book document (step 1);
- performing a preliminary luminance correction calculation using a same correction value candidate for a luminance value of a background pixel positioned on a line parallel to the binding portion of the book document (step 2);
- integrating an absolute value of a difference between a value obtained by the preliminary luminance correction calculation and a luminance value of a neighboring background pixel positioned in the first direction with respect to background pixels on the line, and selecting a correction value candidate that minimizes the integrated value among a plurality of correction value candidates as a correction value of the background pixel on the line (step 3);
- calculating a cumulative luminance correction value for each line by successively performing a luminance correction calculation in neighboring order of the line based on the selected correction value (step 4);
- extracting a shadow region of at least one of a shadow of a binding portion or a shadow of a front edge portion involved in the image data based on the cumulative luminance correction value (step 5);
- and
- performing a luminance correction on the shadow region based on the cumulative luminance correction value (step 6).
A computer-readable medium storing instructions which, when executed by an apparatus, causes the apparatus to perform operations comprising:
- obtaining image data generated by scanning and reading a book document placed on a platen of an image scanner;
- determining a target pixel of the image data as a background pixel when a difference between the target pixel and a neighboring pixel is less than a threshold, the neighboring pixel being in a first direction perpendicular to a binding portion of the book document;
- performing a preliminary luminance correction calculation using a correction value candidate for a luminance value of a background pixel positioned on a line parallel to the binding portion of the book document;
- selecting a correction value candidate from a plurality of correction value candidates as a correction value of the background pixel on the line;
- calculating a cumulative luminance correction value for each line by successively performing a luminance correction calculation in neighboring order of the line based on the selected correction value;
- extracting a shadow region of at least one of a shadow of a binding portion or a shadow of a front edge portion included in the image data based on the cumulative luminance correction value;
- and
- performing a luminance correction on the shadow region based on the cumulative luminance correction value.
Dependencies are inferred from the claim text.