An image processing device, comprising: an extracting unit configured to extract boundaries of a document in a first direction and roughly-detected document corners in a document image captured for the document; characterized in that the image processing device further comprises: a determining unit configured to determine page corners of the document on the boundaries of the document in the first direction around the roughly-detected document corners; and a selecting unit configured to select the page corners with the closest intra-page area pixel feature to a page corner pixel feature of the document among the page corners as document corners, wherein the intra-page area pixel feature of a page corner refers to a pixel feature of the captured document image, belonging to an area inside the document in proximity to the page corner, and the page corner pixel feature of the document refers to a pixel feature included in a page corner area of the document, wherein the first direction is a horizontal direction or a vertical direction of the document image, wherein the extracting unit comprises: a first processing sub-unit configured to obtain a foreground area of the document image in a global binarization method to obtain four edges which surround the foreground area in the direction of upper, bottom, left and right and to determine intersections between the intersected edges of the foreground area as the roughly-detected document corners; and a second processing sub-unit configured to detect boundaries between the roughly-detected document corners in the first direction in a dynamic programming method as the boundaries of the document in the first direction. an extracting unit configured to extract boundaries of a document in a first direction and roughly-detected document corners in a document image captured for the document; characterized in that the image processing device further comprises: a determining unit configured to determine page corners of the document on the boundaries of the document in the first direction around the roughly-detected document corners; and a selecting unit configured to select the page corners with the closest intra-page area pixel feature to a page corner pixel feature of the document among the page corners as document corners, wherein the intra-page area pixel feature of a page corner refers to a pixel feature of the captured document image, belonging to an area inside the document in proximity to the page corner, and the page corner pixel feature of the document refers to a pixel feature included in a page corner area of the document, wherein the first direction is a horizontal direction or a vertical direction of the document image, wherein the extracting unit comprises: a first processing sub-unit configured to obtain a foreground area of the document image in a global binarization method to obtain four edges which surround the foreground area in the direction of upper, bottom, left and right and to determine intersections between the intersected edges of the foreground area as the roughly-detected document corners; and a second processing sub-unit configured to detect boundaries between the roughly-detected document corners in the first direction in a dynamic programming method as the boundaries of the document in the first direction. a determining unit configured to determine page corners of the document on the boundaries of the document in the first direction around the roughly-detected document corners; and a selecting unit configured to select the page corners with the closest intra-page area pixel feature to a page corner pixel feature of the document among the page corners as document corners, wherein the intra-page area pixel feature of a page corner refers to a pixel feature of the captured document image, belonging to an area inside the document in proximity to the page corner, and the page corner pixel feature of the document refers to a pixel feature included in a page corner area of the document, wherein the first direction is a horizontal direction or a vertical direction of the document image, wherein the extracting unit comprises: a first processing sub-unit configured to obtain a foreground area of the document image in a global binarization method to obtain four edges which surround the foreground area in the direction of upper, bottom, left and right and to determine intersections between the intersected edges of the foreground area as the roughly-detected document corners; and a second processing sub-unit configured to detect boundaries between the roughly-detected document corners in the first direction in a dynamic programming method as the boundaries of the document in the first direction. a first processing sub-unit configured to obtain a foreground area of the document image in a global binarization method to obtain four edges which surround the foreground area in the direction of upper, bottom, left and right and to determine intersections between the intersected edges of the foreground area as the roughly-detected document corners; and a second processing sub-unit configured to detect boundaries between the roughly-detected document corners in the first direction in a dynamic programming method as the boundaries of the document in the first direction.