Document image analysis apparatus



<P>PROBLEM TO BE SOLVED: To accurately detect unwanted streaks in an image generated during printing of a document. <P>SOLUTION: An image analysis apparatus includes a step of detecting a luminance gradient direction of each of pixels constituting the image and its strength, based on Y (luminance) data of images of a document, respectively (S105). While switching a pixel to be defined as a pixel of interest sequentially over an entire screen, pixels being present within a predetermined region (e.g., a rectangular region of five pixels respectively in longitudinal and lateral directions) around the pixel of interest are then classified based on the luminance gradient direction of these pixels (S106). When the pixels within the predetermined region are classified eccentrically to a specific direction range group and there is considerable luminance fluctuation in the luminance gradient direction in the pixel of interest, the pixel of interest is determined as an edge pixel (S107). Further, based on a distribution density of pixels determined to correspond to the edge pixel, presence of unwanted streaks in the document is discriminated and moreover, a direction of the unwanted streaks is discriminated based on the luminance gradient direction of the edge pixels (S108). <P>COPYRIGHT: (C)2011,JPO&INPIT
【課題】原稿の印刷の際に生じた画像の不要なスジを精度良く検出する。 【解決手段】原稿の画像のY(輝度)データに基づいて、画像を構成する各画素の輝度勾配方向とその強さをそれぞれ検出する(S105)。そして、注目画素とする画素を画面の全体に亘って順次切り換えつつ、注目画素を中心とする所定領域内(例えば縦横5画素ずつの矩形領域)に存在する各画素を、それらの各画素の輝度勾配方向に基づいて分類する(S106)。所定領域内の画素が特定の方向範囲群に偏って分類されており、かつ、注目画素において輝度勾配方向に大きな輝度の変動があれば、その注目画素をエッジ画素であると判定する(S107)。さらに、エッジ画素に該当すると判定された画素の分布密度に基づいて、原稿に不要なスジが存在するか否かの判別を行い、また、各エッジ画素の輝度勾配方向に基づいて、不要なスジの方向を判別する(S108)。 【選択図】図2




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