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United States Patent iw
de Cosnac et al.
[li] 4,075,658  Feb. 21, 1978
 METHOD AND DEVICE FOR ISOLATING FIGURES IN AN IMAGE
 Inventors: Bertrand de Cosnac; Alain Spiwack, both of Paris, France
 Assignee: Commissariat a l'Energie Atomique, Paris, France
 Appl. No.: 681,300
 Filed: Apr. 29,1976
 Foreign Application Priority Data
Apr. 29, 1975 France 75 13434
 Int. CI.* H04N7/18
 U.S. CI 358/96; 358/138
 Field of Search 358/93, 96, 83, 138
 References Cited
U.S. PATENT DOCUMENTS
2,933,008 4/1960 Barnett 358/96
3,354,266 11/1967 Dinenno 358/96
3,674,926 7/1972 Dewey 358/93
3,706,851 12/1972 Froehlich 358/96
3,729,584 4/1973 de Vos 358/280
Primary Examiner—Howard W. Britton
Attorney, Agent, or Firm—Sughrue, Rothwell, Mion,
Zinn and Macpeak
The graphic information contained in the image is converted by means of a television camera to a video signal constituted by a succession of lines, each line being sampled sequentially so as to obtain an ordered series of points which is stored in memory. The method consists in selecting a parent point forming part of an isolated figure of the image. All the points in which the level of blackening on the image exceeds an adjustable threshold value are isolated automatically by marking with an automaton coupled with the memory. All the marked points corresponding to the figure are extracted from the memory and the figure is reconstituted from the points.
10 Claims, 3 Drawing Figures
U.S. Patent Feb. 21, 1978 Sheet 1 of 2 4,075,658
U.S. Patent Feb. 21, 1978 Sheet 2 of 2 4,075,658
METHOD AND DEVICE FOR ISOLATING
FIGURES IN AN IMAGE
This invention relates to an automatic method for 5 isolating figures in an image as well as to a device for the practical application of the method in accordance with the invention.
As is generally known, it is often necessary for processing and analyzing information to isolate a certain 10 number of figures in an image in order to be able to observe them separately and to calculate automatically the parameters which are related to each figure. Moreover, in order to achieve better visualization of said figure and to avoid any risk of oversight, it is important 15 to ensure that isolation of the figures takes place automatically by erasing each figure of the image after processing in order to pass to the following figure.
The method and device in accordance with the invention are advantageously employed in the field of 20 biomedical research for automatic sorting of chromosomes (karyotype) which are attached at the time of a metaphase. In this case the preparation observed under the microscope produces an image which consists of a set of dark grey shapes on a bright background. The 25 problem is therefore as follows: to isolate one figure among others which form part of the same image in order to extract the parameters therefrom.
It is important to ensure that this isolation of figures takes place fairly rapidly and in a reliable manner. 30 Moreover, the memory devices which are associated for the purpose of storing the electrical signals corresponding to the sampling of the image must have a relatively small capacity in order to reduce the cost of the equipment. 35
The present invention provides a method of solving the problem by satisfying the technical criteria which have been mentioned in the foregoing.
The method in accordance with the invention consists in memorizing the graphic information contained 40 in an image, in sampling said image point by point, in coupling with the memory device an isolating automaton which distinguishes the points of the figures with respect to the background by virtue of the definition of a grey level threshold; said automation then isolates the 45 component points of the figure by marking the words in memory.
In more precise terms, the method of isolation of figures in an image according to the invention consists in converting the visual information contained in the 50 image to an electrical video signal obtained by means of a television camera, the video signal being constituted by a succession of lines separated by line-synchronizing pulses, then in sampling said video signal at uniform time intervals so as to obtain an ordered series of points 55 having associated numerical values which are a function of the level of blackening of the points of the initial image, then in storing said ordered series of points in a memory device. The method according to the invention further consists in selecting a parent point which forms 60 part of a figure F,to be isolated and all those points of said figure in which the level of blackening on the image exceeds a threshold of adjustable value are isolated automatically by marking with the aid of an isolating automaton coupled with said memory device, all the 65 marked points corresponding to said figure are extracted from the memory device and said figure F,of the image is reconstituted from said points, whereupon the
process of isolation is repeated for another figure, starting from another parent point.
In order to reduce the size of the memory device required for storage of information, a preferential alternative embodiment of the method according to the invention consists in compressing the information contained in the video signal before storing the ordered series of numerical values in memory. Said compression consists in recording in the memory device two signals having different formats according to the blackening level of the sampling is lower or higher than the adjustable threshold value. In the case of the background signals in which the blackening is lower than the threshold value, the format of the stored word format is a certain number of bits, the value in binary notation of the number of bits written in memory in respect of said points being equal to the length of that portion of the line which corresponds to the background.
The different marking of the points of the image F, will be described hereinafter.
The above-mentioned compression of information makes is possible to employ memories which have a much smaller capacity than those employed in the prior art.
After having completely isolated a figure F, of the image, that is, after having marked all the points corresponding to said figure, and after display and processing of the figure F,-obtained by connecting all these points, said points are all marked by a certain number of bits which are written in memory in such a manner as to ensure that, at the time of isolation of the other figures of the image (Fj,j i), the points of said figure Fi are considered and processed as background points.
Further properties and advantages of the invention will become apparent from the following description of exemplified embodiments which are given by way of explanation and not in any limiting sense, reference being made to the accompanying drawings, wherein:
FIG. 1 is a block diagram showing the different elements of the device for carrying out the method according to the invention;
FIG. 2 is a schematic representation of a video line delivered by the television camera;
FIG. 3 is a block diagram showing the isolating automaton in accordance with the invention.
The device for isolating a figure contained in an image 2 comprises a television camera 4 in which the output signal is scanned by an analog-to-digital converter 6 associated with a clock-pulse generator 8. The output signal of the analog-to-digital converter 6 passes through an image compressor 10 of conventional type in which the associated threshold value is set either by hand or automatically by control means represented by the arrow 12. At the output of the compressor 10, the signals are fed into a memory device 14. The isolating automaton shown at 16 processes the output signals of the memory device and feeds them back to the input of the memory device after marking, via channel 70. The signals are transmitted from the memory device to the isolating automaton 16 via channel 20. The isolating unit or device for designating the parent point is shown at 22; the device 22 along the action channel 24 feeds signals into the memory device via automaton 16 and receives the output signals from said memory device via channel 28. The device 22 is connected to the isolating automaton 16 via channel 30. At the output of the memory device 14, the signals pass through channel 28 into an image decompressor 32, then into a digital-to-analog