GB1374521A - Image reproducing methods and apparatus - Google Patents

Abstract

1374521 Copying by scanning CROSFIELD ELECTRONICS Ltd 2 Jan 1973 [5 Jan 1972] 477/72 Heading H4F In a facsimile system defects in an original are compensated for by producing a copy of the original, marking the defective parts of the copy, e.g. with red paint, to produce a retouching mask, and scanning the retouching mask in synchronism with rescanning of the original or replay from a store of the signals derived from the original when the copy was made. The signals derived by scanning the retouching mask are used to control insertion of replacement signals in place of those corresponding to the defective elements of the original, e.g. by repeating the last signal representing a non-deflective element in that scanned line or by averaging or linear interpolation in one or two dimensions using the signals from surrounding elements. Alternatively the replacement signals may be derived by subtracting a sharp luminance signal from an unsharp luminance signal derived by an unsharp scanner (Fig. 2, not shown). The retouching mask may also be used to control editorial changes, e.g. areas of flesh may be painted blue, detection of the blue painted areas by the mask scanner causing modifications in any flesh tones detected in the original. In one embodiment using digital signals the successive picture signals are stored in a store 12, writing and reading being controlled by respective clock pulse sources connected to switches 16, 20, the output being taken on line 24 from the third last storage location. If a defect is detected by the mask scanner, switch 16 is operated to connect the input clock pulses to a counter 28 and the defective signals are not read into the store 12. When the defect signal from the mask scanner ceases switch 16 is returned to the position shown and the next picture signal is written into store 12, the output of counter 28 also being written into an associated location in the store as a length of fault code, and counter 28 being reset. When this picture signal following the defect is read from location 14x, the length-of-fault code is also read and circuit 30 causes the contacts of switches 20, 26 to switch from their positions shown, reading from store 12 on line 24 being stopped and the output 34 receiving a signal from circuit 36 which derives the average of the two signals preceding the defect and the two signals following the defect. When the count in counter 32, which is receiving the output clock pulses 20, equals the length-of-fault code read from the store; circuit 30 causes the switches 20, 26 to return to their positions shown, the following signals being read from store 12 and counter 32 being reset. For signals not immediately following a defect a zero is stored as the corresponding length-of-fault code in store 12.