In magnifying a multivalued image, binary images are generated by using the respective density levels of the multivalued image as thresholds. The contour of each binary image is equivalent to an equidensity curve corresponding to each density gradient of the original multivalued image. Outline vectors of each binary image are extracted and magnified/smoothed. The contour of each binary image represents an equidensity curve corresponding to each density gradient of the magnified multivalued image. In a binary image area corresponding to a black pixel of each binary image, a pixel having a density equal to the threshold used to generate the binary image is written. This processing is sequentially performed for all the binary images from a low-density binary image to a high-density binary image to generate a multivalued image. The objected multivalued image is subjected to density gradient smoothing processing. As a result, a magnified multivalued image is obtained.

Conversion from odd to non-zero winding number convention for representation of polygons in a graphics system comprises entry of a polygon in a frame buffer using distinguished states. Special scanlines are determined and marked. Special scanlines are those of relative maxima and minima, and those bordering regions where the polygon touches itself. Each of the special scanlines is examined and entries for the polygon on a scanline are marked odd or even (down or up). The polygon is drawn for a second time. During this drawing, the distinguished state (temporary) entered on the first pass is replaced by a down or up state. The state entered is the current direction value, except for entries on special scanlines. For special scanlines the state entered is given by the marked entry in the frame buffer. This value also becomes the current direction value for subsequent entries.

In a device for processing a signal representative of a document image from a document reading unit to thereby reproduce the document image, a first comparator binarizes a multilevel image signal from the document reading unit with a first threshold value to thereby output a first bilevel image signal. A second comparator binarizes the multilevel image signal with a second threshold value to thereby output a second bilevel image signal. An area discriminating circuit outputs, in response to the second bilevel image signal, an area discriminate signal representative of the inside and or outside of an image area of the document image. An area separating circuit outputs, in response to the area discriminate signal and first bilevel image signal, an image signal representative of only an image portion of the first bilevel image signal which corresponds to the area discriminate signal. The device is capable of reproducing both a sheet document and a book document accurately.

An area filling method develops a binary graphic which has a contour described by direction codes of black picture elements into a raster graphic and fills an inside portion of the raster graphic by a raster scan. The area filling method prepares a start position table which defines area filling start positions for each of the direction codes. Then, a region of the binary graphic is scanned in a predetermined direction starting from an area filling start position, which region includes a black picture element which constitutes the contour. Each scanned white picture elements within the region is marked as a first type picture element and a black picture element which is scanned first within the region is marked as a second type picture element. An area filling start position which corresponds to a direction code of the second type picture element is obtained by referring to the start position table, and the region is successively moved with respect to all black picture elements which constitute the contour. A raster scan is made to fill an area based on the first and second type picture elements which are obtained with respect to the contour.

For a reproduction of optical sound information in a double variable-area track (DZ) an optoelectronic converter device scans the optical sound track of a film. The converter device generates a digital image signal for buffer storage in the memory of a program-controlled data processing device. The data processing device derives the profile of the two edges of the double variable-area track from data values of the buffer-stored image signal. Audio data for a sound reproduction are generated using data about the edge profile determined.