Image digitizing systems

• US 4,493,106 A
• Filed: 03/31/1982
• Issued: 01/08/1985
• Est. Priority Date: 12/24/1981
• Status: Expired due to Fees

• Current Assignee: International Computers Limited (Fujitsu Limited)
• Original Assignee: International Computers Limited (Fujitsu Limited)
• Inventors: Miles, Peter R., Farhangi, Hassan, Daskalakis, Costas N.
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US06/363,764
• Time in Patent Office: 1,014 Days
• Field of Search: 382/4, 382/18, 382/51, 382/41, 340/722, 358/166, 358/282, 358/284, 364/553-555
• US Class Current: 382/271
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene

Abstract

An image is scanned by a TV camera 9 and the resultant signal digitized in an analogue to digital converter 12 the output of which represents the measured intensity of each picture element of the image. The values relating to selected lines may be captured in a line store 13. Alternatively the number of picture elements of a selected intensity may be counted during the count of a scan in a level counter 14, using a look-up table 15 as a mask to select the desired level. After all levels have been similarly counted the resultant histogram is modified by mapping each intensity into a new value with a smaller number of bits in such a way as to tend to equalize the number of picture elements in each new level. The new values are loaded into the look-up table 15 and in subsequent scans the measured intensities are converted into the new values, which may be displayed on a monitor 16 or captured in the line store 13.

Claims

1. A system for digitising an image comprising:

means arranged repeatedly to scan an image and on each scan to output an analogue signal representing the image;

conversion means arranged periodically to convert the analogue signal to a digital signal output from the conversion means, the successive values of which signal represent a display value for each individual picture element of the image;

counting means arranged to be operative during each of a plurality of scans to accumulate a count of the number of picture elements in the entire image whose display values meet a selected criterion;

selection means settable to select the said criterion; and

means for resetting the setting for the said selection means between scans of the said plurality in such a manner as to ensure that at the end of the said plurality of scans the sequence of counts accumulated during the said plurality of scans suffices to define a display-value histogram for the picture elements of the image.

2. A system as claimed in claim 1 in which:

the selection means comprises storage means addressed in operation by the said digital signal;

each possible value of the digital signal causing the contents of a corresponding location of the storage means to be read out;

each of the said locations being loadable with a bit to thereby select the display value represented by the value of the digital signal to which that location corresponds;

the said bits when read out being supplied to the said counting means for counting.

3. A system as claimed in claim 2, in which each of the said locations is loadable in addition with a transformed display value, which value is read out when the storage means is addressed by the value of the said digital signal to which its location corresponds.

4. A method of digitising an image which comprises repeatedly scanning an image and on each scan outputting an analogue signal representing the image, periodically converting the analogue signal to a digital signal the successive values of which represent a display value for each individual picture element of the image, and in the course of each of a plurality of scans accumulating a count of the number of picture elements in the entire image whose display values meet a selected criterion, the criterion being varied in successive scans of the said plurality in such a manner that the sequence of counts accumulated during the said plurality of scans suffices to define a display-value histogram for the picture elements of the image.

5. A method as claimed in claim 4, in which the selection is achieved by applying the said digital signal as an addressing signal to storage means, any location of which that corresponds to a value of the digital signal representing a display value that is to be selected being loaded with a bit.

6. A method as claimed in claim 5, in which each of the said locations is loadable in addition with a transformed display value, which value is read out when the storage means is addressed by the value of the said digital signal to which its location corresponds.

7. A method of obtaining a digitised transformed representation of an image which comprises repeatedly scanning an image, on each scan producing an analogue signal representing the image, and periodically converting the analogue signal to an equivalen binary signal the successive values of which each represent a display value for an individual picture element of the image, in a first stage in each of a plurality of scans counting the number of picture elements in the entire image meeting a selected criterion relating to the display value of the picture elements, the criterion being varied between scans of the said plurality of scans in such a manner that at the end of the said plurality of scans the information that has been accumulated suffices to define the number of picture elements of each display value, and calculating for each value of the binary signal a corresponding transformed display value, and then in a subsequent second stage converting, for at least a complete scan of the image, each value of the binary signal to its corresponding transformed display value.