Abstract: Interpolation of gradation levels of an image without degradation of the quality of the image is disclosed. The image is searched in the vertical direction from an objective pixel (Pt) to be subjected to the gradation level interpolation for a high-level pixel (Pvh) located closest to the objective pixel (Pt), and then searched in the horizontal direction from the objective pixel (Pt) for a high-level pixel (Phh) located closest to the objective pixel (Pt). A comparison is made between the high-level pixels (Pvh, Phh) to determine the distance from the objective pixel (Pt) to one of the high-level pixels which is closer to the objective pixel (Pt) as a high-level distance (Dhigh). Similar operation is performed to extract low-level pixels (Pvl, Phl), and a comparison is made therebetween to determine a low-level distance (Dlow). The gradation level of the objective pixel (Pt) is determined based on the high-level distance (Dhigh) and low-level distance (Dlow).

Abstract: All possible image levels of image data are input to tone conversion characteristics, and a tone jump included in the image after tone conversion is detected from the resultant output data. An A-type contour line and a B-type contour line constituting the contours of a target area for tone interpolation are obtained from the multi-tone image. The target area is then detected by checking the inclusive relationship between the A-type and B-type contour lines to extract at least one set of contour lines indicating the contour of the target area. In the target area, an area defined by the A-type contour line and the B-type contour line is divided into (N+1) divided areas, and N intermediate image levels are sequentially allocated to the N divided areas of the (N+1) divided areas.

Abstract: A mask area is specified as a target area of modification in a multi-tone image. The multi-tone image is converted to a plurality of binary images with a plurality of threshold values. A plurality of density-contours corresponding to the plurality of binary images are extracted. Without implementing any contraction or expansion, a portion overlapping the contour of the mask area is deleted from each extracted density-contour. A plurality of modified density-contours which do not include the portions overlapping the contour of the mask area are converted back to a modified multi-tone image.

Abstract: The multi-tone image data is converted to a plural sets of binary image data with a plurality of density levels as threshold values. Contraction and expansion are sequentially executed on the plural sets of binary image data to correct a contour of each binary image. The plural sets of the processed binary image data are re-converted to multi-tone image data which represents a multi-tone image having a corrected contour.

Abstract: The present invention provides an improved technique for extracting contours in an image without waiting for processing of all the scanning lines in the image. Run-data on two boundary scanning lines, each representing the boundary coordinates at which the image changes, are stored in a run-data buffer. A contour extraction unit compares two sets of the run-data with one another to extract segment vectors and detect a set of closed-loop vectors defining a contour of a image area. Three registers in a working buffer store specific data representing the relationship between a starting point and a terminal point of each vector sequence and are used in detecting closed-loop vectors. A vector data memory stores vector data including coordinate values of start and end points of closed-loop vectors.

Abstract: Segment data expressing segments which form the contour of a graphic figure are provided. Connection mode data expressing the connection modes between the segments are generated. The loops included in the graphic figure are detected on the basis of the segment data and the connection mode data. Even if the segments imperfectly define the contour, the loops can be detected through the step of correcting the segment data and the connection mode data.

Abstract: A laser exposure system for use in scanning and recording images, the system comprising subdividing the laser beam from the laser source into several parallel traces of laser beams; modulating the laser beams individually in response to the image signals be means of a multi-channel optical modulator; directing the modulated laser beams through a first mirror and a second mirror so as to enable the laser beams from the second mirror to be in parallel with the reference plane with respect to the sub-scanning direction; varying the distance between the modulator and the first mirror; and adjusting the angles of the first and second mirrors to the reference plane so that a possible decline of the laser beams in the sub-scanning direction is compensated.

Abstract: A laser exposure system for use in scanning and recording images, the system comprising subdividing the laser beam from the laser source into several parallel traces of laser beams; modulating the laser beams individually in response to the image signals by means of a multi-channel optical modulator; directing the modulated laser beams through a first mirror and a second mirror so as to enable the laser beams from the second mirror to be in parallel with the reference plane with respect to the sub-scanning direction; varying the distance between the modulator and the first mirror; and adjusting the angles of the first and second mirrors to the reference plane so that a possible decline of the laser beams in the subscanning direction is compensated.