High quality image copier with exact reproduction of digitally halftoned images
First Claim
1. A method of generating print data from a printed image produced by a printing device operating at a first dots per inch (dpi) value, so that the image is composed of a plurality of dots, the image incorporating defects resulting during printing of the image, such as rotation of a print medium and blemishes of the image, the method comprising the steps of:
- scanning the printed image, at a sampling rate which corresponds to a second dpi value that exceeds the first dpi value by a predetermined factor, which is such that each dot of the image results in the generation of a set of at least two markers;
generating data relating to the position and color value of each marker;
detecting the defects in the image and assigning a data value to such defects;
processing said data and applying the data value assigned to the defects to determine which of each of the markers generated for a respective dot should be recorded as a center for that dot; and
generating print data as a result of the processing step, the print data relating to the position and print value of the markers determined as a result of processing the data.
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Accused Products
Abstract
The invention relates to a method of generating print data from a printed image produced by a printing device operating at a first dots per inch (dpi) value, so that the image is composed of a plurality of dots, the image incorporating defects resulting during printing of the image, such as rotation of a print medium and blemishes of the image. The method includes the step of scanning the printed image, at a sampling rate which corresponds to a second dpi value that exceeds the first dpi value by a predetermined factor so that each dot of the image results in the generation of at least two markers. Data relating to the position and colour value of each marker is generated. The defects in the image are detected and a data value is assigned to such defects. The data is processed and the data value is used to determine which of each of the markers generated for a respective dot should be recorded as a center for that dot. Print data is generated as a result of the processing step, the print data relating to the position and print value of the markers determined as a result of processing the data.
4 Citations
17 Claims
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1. A method of generating print data from a printed image produced by a printing device operating at a first dots per inch (dpi) value, so that the image is composed of a plurality of dots, the image incorporating defects resulting during printing of the image, such as rotation of a print medium and blemishes of the image, the method comprising the steps of:
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scanning the printed image, at a sampling rate which corresponds to a second dpi value that exceeds the first dpi value by a predetermined factor, which is such that each dot of the image results in the generation of a set of at least two markers;
generating data relating to the position and color value of each marker;
detecting the defects in the image and assigning a data value to such defects;
processing said data and applying the data value assigned to the defects to determine which of each of the markers generated for a respective dot should be recorded as a center for that dot; and
generating print data as a result of the processing step, the print data relating to the position and print value of the markers determined as a result of processing the data. - View Dependent Claims (2, 3, 4, 5, 6)
(a) selecting data relating to an initial group of sets of markers and applying the defect value to the selected data to determine which marker of each selected set is to be recorded as related to the center associated with that set;
(b) determining which marker of each set of at least one further set should be recorded as a center of a corresponding dot by using a relationship existing between the positions of the recorded markers of the initial group of sets;
(c) adding data related to the position of the, or each, marker, recorded as a result of the determination, to the data relating to recorded markers of the initial group of sets of markers; and
(d) repeating steps (b) and (c) until print data for a further, substantially identical image is obtained.
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6. A method as claimed in claim 1, which includes the step of printing an image with said apparatus, using said generated print data.
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7. An apparatus for generating print data from a printed image, the apparatus comprising:
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a printing device that operates at a first dots per inch (dpi) value to generate the printed image, so that the image is composed of a plurality of dots, the image incorporating defects resulting during printing of the image, such as rotation of a print medium and blemishes of the image;
a scanning device positioned downstream of the printing device for scanning the printed image, the scanning device being configured to operate at a sampling rate which corresponds to a second dpi value that exceeds the first dpi value by a predetermined factor, which is such that each dot of the image results in the generation of a set of at least two markers, the scanning device being configured to generate data relating to the position and color value of each marker; and
a processor that is connected to the scanning device and is configured to receive said data from the scanning device, the processor being capable of analysing said data for the defects, applying a data value to the defects, and processing said data together with the data value to determine which of each of the markers generated for a respective dot should be recorded as a center for that dot, and generating print data relating to the position and color value of the markers so determined. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
(a) selecting data relating to an initial group of sets of markers and applying the defect value to the selected data to determine which marker of each selected set is to be recorded as related to the center associated with that set;
(b) determining which marker of each set of at least one further set should be recorded as a center of a corresponding dot by using a relationship existing between the positions of the recorded markers of the initial group of sets;
(c) adding data related to the position of the, or each, marker, recorded as result of the determination, to the data relating to recorded markers of the initial group of sets of markers; and
(d) repeating steps (b) and (c) until print data for a further, substantially identical image is obtained.
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14. An apparatus as claimed in claim 13, which includes a memory arrangement that is connected to the processor to store the print data.
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15. An apparatus as claimed in claim 13, in which the processor and the memory arrangement are operatively connected to the printing device so that the printing device can print, on demand, said further, substantially identical image.
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16. A digital camera which includes an apparatus as claimed in claim 7.
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17. A digital camera as claimed in claim 16, in which the processor is defined by a processor unit of a digital camera and the memory arrangement is defined by a memory device of the digital camera.
Specification