Patent GB-1394326-A (GB)
Title: Binary image processor
IPC: G06V10/34
Filed: 1973-05-31
Abstract: 1394326 Pattern recognition systems INFORMATION INTERNATIONAL Inc 31 May 1973 [15 Sept 1972] 26064/73 Heading G4R An image processor for a pattern recognition system includes means for comparing data bytes of stored arrays of bits, representing reference patterns and a pattern to be recognized, in order to generate a result array R. The nature of the result array and the size and position of the bytes are controlled by variable operating parameters. The processor is associated with a memory 21 which contains the arrays, &c. Data from an address register 52 in the processor causes an instruction to be read from the corresponding address in the memory to an instruction register 53 in the processor. The instruction extracts the relevant parameter data from the memory and passes it to a parameter register 54 in the processor. The parameters control read out from the memory of portions of the inkown array U and a reference (or mask) array M for the comparison process. Typically a 3 x 3 block of bits U0-U8 of the array is inspected in relation to a corresponding bit of the M array, Fig. 3. The block is "moved" to scan the whole of the U array. In one mode of operation the best correlation position for the U array relative to the selected M array is determined by performing at 70 a logical function, e.g. EXCL-OR on each of the bits of the block and the M bit. The function depends on the parameter data. If a 1-bit results from any of the 9 operations a corresponding counter 78 is incremented. When the block has been scanned over the whole array the accumulated counts indicative of the shape similarity are stored. Also, the counter holding the highest count indicates the best correlation position, and this indication is also stored in the memory 21. A result array R is generated in a "density' mode. In this mode the arithmetic value of a byte from the U array is compared at 72 with that of a corresponding byte from the M array. Dependent upon the relative magnitudes a 1 or 0-bit is set in the R array. A result array is also generated in a "binary" mode. In this mode the bits of a 3 Î 3 block of the U array, exluding the centre bit U8, are processed according to a logical function controlled by the parameter bits to provide a new set W of eight bits. In a modification some of the bits of the U array block are replaced by corresponding bits from a previously obtained R array. The set W is used in the determination of the Euler number of connectivity. The W-set is transformed, under the control of other parameters, to an 8-bit E-set. The number (0-9) of 1-bits is counted and compared with a threshold, set by the parameter data. The resulting bit P is combined at 74 with the centre bit U8 of the 3 Î 3 block of the U array and with the corresponding M bit according to a selected logical function, the result being the bit to be set in the R array. The array so generated may exclude isolated 1-bits in the U array. The result array bits are also passed to a unit 84 which inspects a 2 Î 2 bit block shown in Fig. 3. The bits are logically combined to detect the presence of 1-4 1-bits in the block, and to increment a corresponding one of counters 86. The number of 1-bits in R8 is also counted. By taking account of the values shown by the counters the character perimeter length and the average line width can be approximated. The relative number of bodies and holes in the image can be determined whereby to determine whether the image is too fragmented for recognition. The result array may be so generated that the image is in effect smeared or thinned. The P-bit from unit 76 may be generated in dependence on the effect that centre bit U8 has on the connectivity: those 1-bits which do not affect the connectivity are reset to 0, this operation being repeated until the result image line width is one bit wide. Further, patterns which do not touch but nevertheless overlap can be separated as described with reference to Figs. 12a, 12b (not shown), for separate recognition. Reference is made to the use of a graded density mask for determination of the centre of gravity of the image. Since each unknown pattern is compared with a number of masks in turn, knowledge of the previously identified patterns may be used to predict the likely nature of the next pattern and so to choose the order in which the masks are used.