Patent GB-1353912-A (GB)
Title: Binary image processor
IPC: G06V10/36
Filed: 1971-06-22
Abstract: 1353912 Character recognition systems INFORMATION INTERNATIONAL Inc 22 June 1971 [22 June 1970] 29271/71 Heading G4R Data representing successive scan lines of a character to be recognized is passed to three serially connected shift registers 41, 42, 43, Fig. 2, which hold three lines. The last 3 bits in each register are read out, providing successive 3 x 3 bit blocks, each block containing 2 x 3 bits of the previous block. The blocks are fed to logic units 55, 57. These two units are also fed with data representing a single scan line of a known character, the line being stored in shift register 59. The known and unknown character signals are stored in the memory of a computer, not shown, which feeds registers 41, 42, 43, 59. The 9 bits of each block fed to logic unit 57 are subjected to a logical operation defined by a signal on lead 64 from the computer. The unit provides a single bit on each of 9 output leads in respect of each block. The bits are counted in respective counters 70-78 so that when the entire unknown character has passed through registers 41-43 the counters will indicate the relationship of the unknown character to the known character not only at the centred position (corresponding to the central bits of all the blocks) but also for eight shifted positions of the unknown relative to the known character. The counter outputs are fed to the computer and also to unit 79 which indicates to the computer which counter is exhibiting the largest count and consequently which of the 9 positions gives the best correlation between the characters. These outputs may be used to centralize the unknown character relative to the known character by appropriately shifting data within the registers or from one register to the next. The bits of each block are also subjected to logical operations in unit 55, the operations being defined by a signal (Result Code) from the computer. There is produced, in respect of each block, a single result bit R which is fed to serially connected registers 81, 83. The output of the last 3 stages of the first register is fed to the logic unit 55. In unit 55, Fig. 4 (not shown), these 3 bits are combined (91) with the bits of the current block, except for the centre bit, to provide an 8-bit block (V#-V7). This block is operated upon (92) to provide a second 8-bit block (W#-W7) and the second (93) to provide a third block (X#-X7). The particular logical operations performed are controlled by the Result Code signal. The number of 1-bits in the third block is counted (94) and a bit (P) generated whose state depends on the count. This bit is logically combined (96) with the centre bit (U8) of the 9-bit block and the corresponding bit (M) from the known character scan line to provide the result bit R. When the entire unknown character has passed through registers 41-43 corresponding result image data will have been passed from register 83 to the computer. By appropriate choice of the controlling Result Code signal the result image represents a modified form of the unknown character, e.g. the character can be smeared as in an out of focus scan, which may be useful in finding the end of a line of characters, or be thinned, or be broadened to close up small breaks. The last two bits in registers 81, 83 are passed to unit 100, effectively scanning the result image by a 2 x 2 bit block. Unit 100 performs a logical operation on the 4 bits, providing signals to 5 counters 101-105. The counts accumulated represent the number of times certain features occur in the result image. For example the features may be outside corners (2 Î 2 block having only one 1-bit), solid black portions (block having 4 1-bits) &c. These counts are passed to the computer, and from them the perimeter length, mass, average line length, and line thickness can be determined. The computer may determine the connectivity (or Euler number) of the unknown or result characters, and unit 55 can be controlled to remove all bits whose removal does not cause the connectivity to change, so thinning the result images. The centre of gravity may also be found.