1. Field of the Invention
The present invention relates to a method and apparatus for processing a linework image, and more particularly to a method and apparatus for finding and reconnecting a break in a linework image.
2. Description of the Related Art
A block copy is prepared as an original of characters and lineworks in a prepress process for a color printing plate. The block copy is formed by arranging phototype-setting characters and drafted keylines on a layout sheet in the same dimensions and quality as the final products. Instructions for the subsequent processes are also given on the layout sheet; that is, the layout sheet acts as an instruction paper for the prepress process.
Tint laying is generally performed in the prepress process. Tint laying is processing in which a specified region within an image is uniformly filled with a desired color. Automatic tint laying is employed in some of the modern image processing systems. In such systems, tint laying is completed, for example, by obtaining binary image data of a block copy image with an image scanner and filling a certain closed region in the block copy image with a desired color with an image processor.
A linework, which is supposed to define a closed region in a block copy image, is sometimes found incomplete or broken when filling of the closed region is executed. The incomplete or broken linework is generally attributable to an incomplete draft or layout sheet, or unsuccessful image reading with an image scanner.
Line breaks are generally reconnected manually; an operator directly detects line breaks in a block copy image displayed on a CRT and fills them to correct the block copy image.
A line break has generally a width of one to several pixels. Accordingly, only experienced operators can efficiently detect breaks on the CRT. When there are several breaks in a linework, it takes rather a long time to detect and reconnect all of them.
JAPANESE PATENT LAYING-OPEN GAZETTE No. Sho-61-139892 proposes a method of reconnecting line breaks which utilizes a technique of changing binary image data into vector data. Vector data processors for executing this method are rather complicated and expensive.
On the other hand, those image processors for processing lineworks (hereinafter referred to as linework processors), which change the level of binary image data for each pixel, are relatively simple. Accordingly, addition of a specific function of vector data processing to linework processors drastically increases the price of the processors.
Furthermore, the method including vector data processing does not perfectly detect line breaks and requires operators confirmation for the existence thereof. It means that the total time for processing is not shortened greatly.