Abstract: An original image is divided into a plurality of pixel blocks each consisting of a plurality of pixels. A density histogram represented by an electric signal is obtained for each pixel block. Respective pixel blocks are analyzed to find adjacent pixel blocks which are uniform and continuous in density. If the pixel blocks thus found are continuous in density with the reference pixel blocks located at the corner of the original image, the pixel blocks are regarded as those representing the background portion of the original image. The numbers of pixels in the density histogram is corrected for each background pixel block, and highlight and shadow points for determining a gradation curve is determined. The gradation curve is set in a signal-converter to convert an image signal representative of the original image.

Abstract: An original image is divided into a plurality of pixel blocks each consisting of a plurality of pixels. A density histogram represented by an electric signal is obtained for each pixel block. Respective pixel blocks are analyzed to find adjacent pixel blocks which are uniform and continuous in density. If the pixel blocks thus found are continuous in density with the reference pixel blocks located at the corner of the original image, the pixel blocks are regarded as those representing the background portion of the original image. The numbers of pixels in the density histogram is corrected for each background pixel block, and highlight and shadow points for determining a gradation curve is determined. The gradation curve is set in a signal-converter to convert an image signal representative of the original image.

Abstract: On a conversion plane of image data, first through third points (Q.sub.H, Q.sub.S, Q.sub.D) are provided. The first and second points are determined in accordance with highlight and shadow points of an original image, respectively, while the third point is determined in accordance with a dummy shadow point of the original image. A conversion curve (C.sub.a, C.sub.b) is so determined as to pass through the first and second points and to extend along a straight line (L) connecting the first and third points in the highlight region of the coordinate plane.

Abstract: A color original image is pre-scanned in order to detect respective color components of sample pixels. Then, it is decided whether each sample pixel has color components corresponding to a designated "memory color" within a predetermined allowable error range. A "memory color" represents colors with respect to which persons have preconceived notions, i.e., memories, as to their correct tone, hue, etc., for example, the color of the sky, trees, or the like. When the number of sample pixels having the memory color is larger than a threshold value, a predetermined color separation rule is corrected to obtain a corrected color separation rule which is used for separating the color original image into components suited for reproduction of an image corresponding thereto.

Abstract: An original image is read with an image reader for each pixel, whereby color component signals (Yi, Mi, Ci, Ki) expressing the original image are obtained. A sharp signal generator extracts the gray component from the combination of the color component signals, to output the gray component as a sharp signal (S.sub.O). The difference between the sharp signal (S.sub.O) and an unsharp signal (U) is linearly combined with the color component signals, to thereby give sharpness-enhanced signals (ES.sub.Y, ES.sub.M, ES.sub.C, ES.sub.K).

Abstract: A color scanner capable of displaying a plurality of images in parallel comprises a scanning head for scanning a plurality of images for inputting image signals thereof; a first memory for storing image signals of the plurality of images inputted by the scanning head; a color correction circuit for correcting image signals stored in the first memory to set desired conditions for reproduction; an output skipping circuit for reducing the number of image signals corrected by the color correction circuit to a predetermined number so that they can be displayed on a color monitor; a second memory for storing image signals of the plurality of images skipped by the output skipping circuit; and a color monitor for simultaneously displaying on one screen the plurality of images corrected, based on the image signals stored in the second memory.

Abstract: A method of and an apparatus for heating a road surface, in which hot air controlled to a predetermined temperature is blown against the road surface so as to heat the road surface. The apparatus includes a hot air generator provided with a burner and a thermal control unit, and a duct formed with blowing pores for blowing the hot air against the road surface.