EP0576003A1
Expired / Lapsed
EP
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Apparatus for converting image signal representing image having gradation
Assignee: Dainippon Screen Manufacturing Co Ltd
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Filing: 1993-06-24
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Granted: —
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Expires: 2013-06-24
Abstract
Abstract First density histogram generation means (8A) generates a first density histogram based on a first image signal which is obtained by reading a data read region. Of peak portions formed in the first density histogram, the density rank value of a peak portion which satisfies a predetermined condition is detected. Pixel-to-be-removed detection means (8C) determines pixels-to-be-removed whose average densities are included in a pixel removal density range which corresponds to said detected peak portion density rank value. Regarding all pixels without said pixels-to-be-removed, a second density histogram is generated. Based on the second density histogram, cumulative density histogram is generated to thereby find a highlight point and a shadow point through which a gradation curve must passes. Then, the gradation curve is established, in accordance with which an image processing part (3) converts the first image signal into a second image signal.
Inventors
- 👤 Yasuharu c/o Dainippon Screen Mfg.Co. Yonezawa
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 20:27
CPC Classifications
G; G06; G06T; G06T5/00; G06T5/90; G06T5/92; G06T5/40; G06V; G06V10/00; G06V10/20; G06V10/28; H; H04; H04N; H04N1/00; H04N1/40; H04N1/407; H04N1/4072; H04N1/4074
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
331 words
An image signal conversion apparatus for converting a first image signal representative of an original image having gradation into a second image signal to modify said gradation, wherein said original image consists of a pixel array and said first image signal represents respective densities of pixels included in said pixel array, said image signal conversion apparatus being characterised by comprising: (a) means for classifying said pixels into a plurality of density ranks in accordance with the respective values of said first image signal and generating a first density histogram representing the number of pixels which belong to the respective density ranks, said first density histogram including at least one peak portion; (b) means for extracting a peak portion which satisfies a predetermined condition from said at least one peak portion to thereby obtain a detected peak portion; (c) means for calculating a pixel removal density range in accordance with a density rank value which corresponds to said detected peak portion; (d) means for extracting pixels whose value of said first image signal belongs to said pixel removal density range from pixels which form said data read region to thereby obtain pixels-to-be-removed; (e) means for classifying pixels which remain after removal of said pixels-to be-removed from said pixels which form said data read region into a plurality of density ranks in accordance with the values of said first image signal to thereby generate a resultant density histogram representing the number of pixels which belong to the respective density ranks; (f) means for determining a reference point on a gradation conversion coordinate plane in accordance with the resultant density histogram; (g) means for determining signal conversion characteristics in accordance with said reference point; (h) means for setting said signal conversion characteristics in a signal convertor; and (i) means for inputting said first image signal to said convertor and receiving an output signal from said signal convertor as said second image signal, whereby said first image signal is converted into said second image signal.
Claim 2
Dependent Claim
259 words
An image signal conversion apparatus according to claim 1, wherein the extracted peak portion satisfies a predetermined first condition which corresponds to said peripheral region from said at least one peak portion to thereby obtain a first removal candidate peak portion and the apparatus further comprises: (j) means for classifying pixels which remain after removal of pixels which are included in a pixel distribution surge portion around said first removal candidate peak portion from the pixels which form said data read region into a plurality of density ranks in accordance with the respective values of said first image signal and generating a second density histogram representing the number of pixels which belong to the respective density ranks, said second density histogram including at least one peak portion; (k) means for extracting a peak portion which satisfies a predetermined second condition which corresponds to said peripheral region from said at least one peak portion of said second density histogram to thereby obtain a second removal candidate peak portion; (l) means for comparing the density of said first removal candidate peak portion with the density of said second removal candidate peak portion; and (m) means for selecting a removal cancel peak portion from said first and said second removal candidate peak portions in accordance with a result of said comparison and the means (c) for calculating a pixel removal density range calculates a pixel removal density range which includes a peak portion which remains after excluding said removal cancel peak portion from said first and said second removal candidate peak portions.
Claim 3
Dependent Claim
101 words
The image signal conversion apparatus of claim 1 or 2, wherein said subject region is a subject region of a reversal positive film, wherein said means (b) comprises: (b-1) means for detecting a first peak portion of the lowest density part of the density range of said first density histogram; and (b-2) means for detecting a second peak portion of the highest density part of the density range of said first density histogram, and wherein said detected peak portion includes said first peak portion and said second peak portion which are detected by said means (b-1) and said means (b-2), respectively.
Claim 4
Dependent Claim
71 words
The image signal conversion apparatus of claim 3, wherein said first peak portion is located within a first detection density range which is set at a lower density side end of the density range of said first density histogram, and wherein said second peak portion is located within a second detection density range which is set at a higher density side end of the density range of said first density histogram.
Claim 5
Dependent Claim
39 words
The image signal conversion apparatus of claim 4, wherein said first detection density range and said second detection density range are set in such a manner that they do not overlap the density range of said subject region substantially.
Claim 6
Dependent Claim
64 words
The image signal conversion apparatus of claim 3, wherein said means (k) comprises: (k-1) means for detecting a highest density side peak portion which is located nearest to a higher density side end of the density range of said second density histogram, and wherein said second removal candidate peak portion includes said highest density side peak portion which is detected by said means (k-1).
Claim 7
Dependent Claim
71 words
The image signal conversion apparatus of claim 6, wherein said means (m) comprises: (m-1) means for determining said first removal candidate peak portion which is located nearer to the higher density side end as said removal cancel peak portion if the density of said second removal candidate peak portion is higher than the density of said first removal candidate peak portion which is located nearer to the higher density side end.
Claim 8
Dependent Claim
81 words
The image signal conversion apparatus of claim 1 or 2, wherein said subject region is a subject region of a negative film, wherein said means (b) comprises: (b-3) means for detecting peak portions which are located at the lowest and the second lowest parts of the density range of said first density histogram, and wherein said detected peak portion includes said peak portions which are located at the lowest and the second lowest parts which are detected by said means (b-3).
Claim 9
Dependent Claim
67 words
The image signal conversion apparatus of claim 8, wherein said means (b) further comprises: (b-4) means for setting a third detection density range at the lower density side end of the density range of said first density histogram, and wherein said means (b-3) comprises means for detecting in said third detection density range said peak portions which are located at the lowest and the second lowest parts.
Claim 10
Dependent Claim
38 words
The image signal conversion apparatus of claim 9, wherein said means (b-4) comprises means for setting said third detection density range so that third detection density range does not overlap the density range of said subject region substantially.
Claim 11
Dependent Claim
56 words
The image signal conversion apparatus of claim 8, wherein said means (k) comprises: (k-2) means for detecting a first peak which is located at the lowest part of the density range of said second density histogram, and wherein said second removal candidate peak portion includes said first peak portion which is detected by said means (k-2).
Claim 12
Dependent Claim
65 words
The image signal conversion apparatus of claim 11, wherein said means (f) comprises: (f-2) means for determining said first removal candidate peak portion which is located at the lowest part as said removal cancel peak portion if the density of said second removal candidate peak portion is lower than the density of said first removal candidate peak portion which is located at the lowest part.
Claim 13
Dependent Claim
284 words
The image signal conversion apparatus of claim 1 or 2, wherein said means (d) comprises: (d-1) means for preparing a mask having a pixel range of a predetermined size; (d-2) means for overlapping said mask on a portion of the image of said data read region; (d-3) means for dividing pixels of said portion of said data read region into first pixels having densities which belong to said pixel removal density range and second pixels having densities which do not belong to said pixel removal density range and assigning a first and a second value to said first and said second pixels, respectively, whereby first binarization is attained; (d-4) means for calculating an average value of said first and said second values, which are assigned by said first binarization, as to the pixels of said portion of said data read region and replacing a value of a pixel which is located at a centre within said mask with said average value to thereby obtain a pixel which has a converted value; (d-5) means for gradually changing the position of said mask on the image of said data read region while repeating the operations of said means (d-1) to (d-4) to thereby obtain a plurality of pixels each having a converted value; (d-6) means for dividing said plurality of pixels each having said converted value into third pixels and said fourth pixels using a predetermined threshold value and assigning a third and a fourth value to said third and said fourth pixels, respectively, whereby second binarization is attained; and (d-7) means for determining said pixels-to-be-removed in accordance with said third and said fourth values which are assigned to the respective pixels by said second binarization.
Claim 14
Dependent Claim
41 words
The image signal conversion apparatus of claim 1, wherein said means (c) comprises: (c-1) means for setting said pixel removal density range in a predetermined density range which includes a density value corresponding to said detected peak portion as a centre.
Claim 15
Dependent Claim
51 words
The image signal conversion apparatus of claim 2, wherein said means (c) comprises: (c-1) means for setting said pixel removal density range in a predetermined density range around a peak portion of each one of said first and said second removal candidate peak portions except for said removal cancel peak portion.
Claim 16
Dependent Claim
88 words
The image signal conversion apparatus of claim 14 or 15, wherein said means (f) comprises: (f-1) means for accumulating appearance frequencies of the pixels of the respective density ranks in accordance with said second density histogram to thereby generate a cumulative density histogram; (f-2) means for applying a cumulative appearance frequencies which has been found in advance to said cumulative density histogram to thereby find a reference density; and (f-3) means for applying said reference density to said gradation conversion coordinate plane to thereby find said reference point.
Claim 17
Dependent Claim
31 words
The image signal conversion apparatus of any preceding claim, wherein the image of said data read region is a colour image, and wherein said first image signal includes colour component signals.
Claim 18
Dependent Claim
36 words
The image signal conversion apparatus of any preceding claim, wherein said means (a) comprises: (a-1) means for averaging said colour component signals of each pixel to thereby obtain said respective values of said first image signal.
Claim 19
Dependent Claim
40 words
The image signal conversion apparatus of any preceding claim, wherein said means (a) comprises (a-2) means for finding said respective values of said first image signal in accordance with the respective values of said colour component signals of each pixel.
Claim 20
Dependent Claim
48 words
The image signal conversion apparatus of any preceding claim, wherein said means (a) comprises: (a-3) means for selecting one of said colour component signals; and (a-4) means for finding said respective values of said first image signal in accordance with the respective values of selected colour component signals.
References Cited (Backward Citations)
EP0283255A2
Cited
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