"Black" runs thinned from a substantially two-tone original pattern and having a pattern stroke width of a substantially single picture element are classified into four states where a black run in a present scanning line is (1) linked with a leading side of black run in a next previous line, (2) linked with a trailing side of the latter, (3) aligned with the latter in both sides, and (4) not linked with the latter. The former is defined to be linked with the latter when they have either a vertex or a side of a picture element alone in common. The former is encoded according to the successively classified states by using, for states (1) and (2), a black run length. For state (4), the black run length is used in combination with a "white" run length measured up or down to the leading side of the former, if any, from the trailing side of that black run in the previous line which either next leads the former or has more common picture element side or sides than specified on defining linkage with leading and/or trailing sides staggered in relation to the corresponding sides of the former. Thinning processes are iterated preferably not transforming a "black" picture element into a "white" one when situated, in addition to known neighborhood conditions, at a vertex of an acute "black" triangle. The encoded signal is decoded and then subjected to iterative thickening processes into a reproduction approximately representative of the original.
A character image data compression system for compressing binary data from an image corresponding to a two-dimensional character image, making it possible to optionally output the coded data in conformity with the characteristic of a character image having complicated composition, thereby to improve the data compression ratio as a whole character and make the capacity of a character data memory compact.
An image processing method comprising the step of converting a read image signal into an intermediate code which is then stored in an image memory. The method further includes the steps of reading out the stored intermediate code and converting the pixel density of the read-out intermediate code. Then, the intermediate code, the pixel density of which has been converted, is converted into a final code.
Two-dimensional pattern detecting apparatus provided with register for serially receiving binary signals obtained from analog signals of a two-dimensional pattern and adapted to divide the pattern into pixels and to represent the density of bright and dark for pixels by the binary signals. The apparatus further includes a processing circuit adapted to compare with predetermined patterns a pattern composed of 8 peripheral pixels of a partial area of 3.times.3 pixels within the two-dimensional pattern, on the basis of the binary signals stored in the register. The processing circuit outputs a binary signal of a logic value stored in said register corresponding to a central pixel of the partial area when the pattern of the 8 pixels coincides with one of said predetermined patterns, and to outputs a binary signal of a logic value prevailing in 8 binary signals stored in the register corresponding to the 8 pixels when the pattern of the 8 pixels does not coincide with any of the predetermined patterns.
In this invention, an original image is read to be formed as a tour bit map, and the bit map is read out for each plurality of picture elements. Then, in the position to which the aforementioned unit plurality of picture elements corresponds on the original image, a predetermined bit map data is to be written by a logical sum. If the operation is indicated as a shadowing process, a bit map of a predetermined oblique line for a shadow designated by a direction and a length is to be written. The aforementioned operation is carried out for every plurality of picture elements on the contour bit map so as to thicken or shadow the original image at a high speed. When the method of this invention is applied as to a large size region, since the work area for the reservation of the contour data becomes larger to exhibit less effectiveness of the space usage, the processing area is designed to be divided, if required, to be processed. In such a division method, it is required to set up as work areas a reservation area for keeping the contour bit map and a writing-in region for writing in the synthetic unit data in the use of the logical sum. Providing the latter mentioned writing-in region makes it possible to save a clipping treatment, and also give an advantage for effecting the thinning operation.
A system is disclosed for arithmetically compressing bi-level data of an image by sampling history pels, which are adjacent pels to a current pel to be processed, and pels so separated from the adjacent pels as to adapt to a period of a dither matrix for a dither image. From the sampled pels it is determined whether the sampled image has a dither dominant image pattern or a text-graphic dominant image pattern and an appropriate signal is generated, a first signal representing that the image has the dither dominant image pattern, a second signal representing that the image has the text-graphic dominant image pattern, and a third signal representing that the image is not classified as either of these image patterns. The first, second and third signals are applied to an up-down counter which accumulates the occurrences of the signals to produce, when the accumulated value exceeds an upper threshold or a lower threshold, a control signal for selectively switching access to first and second statistical tables, which store, at each entry, the more probable symbol and the probability of the less probable symbol for the image of the text-graphic image and the dither image, respectively.
