JPS6336713B2 - - Google Patents
Info
- Publication number
- JPS6336713B2 JPS6336713B2 JP56143418A JP14341881A JPS6336713B2 JP S6336713 B2 JPS6336713 B2 JP S6336713B2 JP 56143418 A JP56143418 A JP 56143418A JP 14341881 A JP14341881 A JP 14341881A JP S6336713 B2 JPS6336713 B2 JP S6336713B2
- Authority
- JP
- Japan
- Prior art keywords
- threshold
- block
- image
- matrix
- pixels
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Links
- 239000011159 matrix material Substances 0.000 claims description 36
- 238000003672 processing method Methods 0.000 claims description 9
- 230000015654 memory Effects 0.000 description 25
- 238000000034 method Methods 0.000 description 24
- 238000010586 diagram Methods 0.000 description 12
- 230000033458 reproduction Effects 0.000 description 9
- 230000009897 systematic effect Effects 0.000 description 6
- 230000006866 deterioration Effects 0.000 description 2
- 230000002542 deteriorative effect Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/40—Picture signal circuits
- H04N1/40062—Discrimination between different image types, e.g. two-tone, continuous tone
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/40—Picture signal circuits
- H04N1/40087—Multi-toning, i.e. converting a continuous-tone signal for reproduction with more than two discrete brightnesses or optical densities, e.g. dots of grey and black inks on white paper
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Physics & Mathematics (AREA)
- Discrete Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Image Processing (AREA)
- Facsimile Image Signal Circuits (AREA)
Description
【発明の詳細な説明】
本発明は、フアクシミリ等において、各画素ご
とには白黒２値で記録しながら、黒画素の密度変
調によつて擬似的に中間調を再現するための中間
調信号処理方式に関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention provides halftone signal processing for pseudo-reproducing halftones by density modulation of black pixels while recording each pixel in black and white binary in facsimile machines and the like. It is related to the method.
従来、この種の中間調信号処理方式としては、
各画素位置に対して、あらかじめ定められた閾値
レベルと各画素の画信号レベルを比較して、閾値
レベルよりも画信号レベルが大きい場合を黒、小
さい場合を白とすることにより、擬似的に中間調
を再現する組織的２値デイザ法が主であつた。 Conventionally, this type of halftone signal processing method is
By comparing the image signal level of each pixel with a predetermined threshold level for each pixel position, and setting the image signal level higher than the threshold level as black, and when it is smaller than the threshold level as white, the pseudo The systematic binary dither method that reproduces halftones has been the main method.
しかし、この方法では、単純に２値化する記録
に比べて分解能が劣化するため、文字部分など高
分解能を要する部分の画質が悪くなる欠点があつ
た。また、文字部分など高分解能を要する部分の
画質を向上させることが、輪郭を強調することに
なり濃淡画像の品質を劣化させる原因となつた。 However, this method has the disadvantage that the resolution deteriorates compared to simple binarization recording, resulting in poor image quality in areas that require high resolution, such as character areas. Furthermore, improving the image quality of parts that require high resolution, such as character parts, emphasizes the outlines, which causes deterioration in the quality of grayscale images.
写真等の濃淡画像を再現しながら文字部分の画
質を劣化させないためには、写真等の濃淡画像領
域と文字等の２値画像領域を識別して、濃淡画像
領域は組織的２値デイザ法を用い、２値画像領域
は単純に２値化することによつて記録することが
考えられるが、濃淡画像領域と２値画像領域を識
別するための良好な方法がなかつた。たとえば、
濃淡画像領域では濃度変化が少ないので、組織的
２値デイザ法により２値化したあとの白黒画情報
の周期性の有無から概略識別することはできる
が、同じ周期性を持つ２値画像を濃淡画像と識別
するという欠点があつた。また、濃淡画像と２値
画像との境界で画質劣化が起る問題があつた。 In order to reproduce grayscale images such as photographs without deteriorating the image quality of text, it is necessary to distinguish between grayscale image areas such as photographs and binary image areas such as characters, and apply systematic binary dithering to grayscale image areas. It is conceivable to record binary image areas by simply binarizing them, but there has been no good method for distinguishing between grayscale image areas and binary image areas. for example,
Since there is little change in density in the grayscale image area, it is possible to roughly identify the presence or absence of periodicity in the black and white image information after binarization using the systematic binary dither method. The problem was that it could be identified as an image. Further, there was a problem that image quality deteriorated at the boundary between the grayscale image and the binary image.
本発明は、これらの欠点を除去するため、画面
を複数画素からなるブロツクに分割し、各ブロツ
ク内の最も濃度レベルの高い画素と最も濃度レベ
ルの低い画素との間の濃度レベル差の値によつ
て、ブロツク単位ごとに、２値画像領域、濃淡画
像領域、さらに両領域の中間の性質を持つ中間領
域に分類し、個々に別々の処理を行うようにした
もので、以下図面について詳細に説明する。 In order to eliminate these drawbacks, the present invention divides the screen into blocks consisting of multiple pixels, and calculates the difference in density level between the pixel with the highest density level and the pixel with the lowest density level in each block. Therefore, each block is classified into a binary image area, a grayscale image area, and an intermediate area with properties between these areas, and each area is processed separately.The drawings are detailed below. explain.
第１図は、本発明の実施例の説明図であつて、
破線で示す小さい正方形は１画素を、実線で示す
大きい正方形１乃至８はそれぞれ１つのブロツク
を表わしている。また、各画素ごとに示されてい
る数字は、原稿より読みとつた濃度レベルであ
り、０が白、16が黒、その間の数字は灰色を示
す。なお、第１図の濃度レベルは便宜上整数で表
わしているが必ずしも整数である必要はない。 FIG. 1 is an explanatory diagram of an embodiment of the present invention,
A small square indicated by a broken line represents one pixel, and large squares 1 to 8 indicated by a solid line each represent one block. Further, the number shown for each pixel is the density level read from the original, with 0 representing white, 16 representing black, and numbers in between representing gray. Note that although the density levels in FIG. 1 are expressed as integers for convenience, they do not necessarily have to be integers.
第２図は、Bayerの閾値配列を縦、横ともそれ
ぞれ４画素ごとにくり返す（以下、４×４の閾値
マトリツクスと称する）ものであり、第３図は、
第２図の閾値マトリツクスを用いて２値化したも
のである。 Figure 2 shows Bayer's threshold array repeated every 4 pixels both vertically and horizontally (hereinafter referred to as a 4x4 threshold matrix), and Figure 3 shows the following:
It is binarized using the threshold value matrix shown in FIG.
本発明の方法では、まず各ブロツクごとにその
内部にある各画素の濃度レベルを比較して最大値
Pmaxと最小値Pminを検出する。たとえば、17
階調の場合第１図において、ブロツク１では、
Pmin＝２、Pmin＝０、ブロツク２では、Pmax
＝４、Pmin＝３、ブロツク３では、Pmax＝５、
Pmin＝０、ブロツク４ではPmax＝13、Pmin＝
０である。ここで、濃度レベルの最大値Pmaxと
最小値Pminの差Ｐ△をあらかじめ定められた値
m1、m2（０≦m1≦m2≦16）と比較し、(i)Ｐ△≧
m2 (ii)m2＞Ｐ△≧m1 (iii)Ｐ△＜m1の３通りに
分類する。 In the method of the present invention, first, the density levels of each pixel within each block are compared and the maximum value is determined.
Detect Pmax and minimum value Pmin. For example, 17
In the case of gradation, in Figure 1, in block 1,
Pmin=2, Pmin=0, in block 2, Pmax
= 4, Pmin = 3, in block 3, Pmax = 5,
Pmin=0, Pmax=13 in block 4, Pmin=
It is 0. Here, the difference P△ between the maximum value Pmax and the minimum value Pmin of the concentration level is set to a predetermined value.
Compare m 1 , m 2 (0≦m 1 ≦m 2 ≦16), (i)P△≧
Classify into three ways: m 2 (ii) m 2 >P△≧m 1 (iii) P△<m 1 .
(i)のＰ△≧m2の場合については、文字等の２
値画像領域であると判定して分解能の良い２値化
処理方法をとる。たとえば、通常の２値記録と同
様に１つの閾値ｈで画信号レベルと比較し、ブロ
ツク内の白画素・黒画素を決める。 In the case of P△≧m 2 in (i), 2 characters, etc.
It is determined that it is a value image area, and a binarization processing method with good resolution is used. For example, as in normal binary recording, a single threshold value h is used to compare the image signal level to determine white pixels and black pixels within a block.
(iii)のＰ△＜m1については、写真等の濃淡画像
領域であると判定して擬似的に中間調を再現する
処理を行う。たとえば、第２図に示すような４×
４閾値マトリツクスを用いて２値化する。 Regarding PΔ<m 1 in (iii), it is determined that it is a grayscale image area such as a photograph, and processing is performed to reproduce a pseudo halftone. For example, 4× as shown in Figure 2.
Binarize using a 4-threshold matrix.
(ii)のm2＞Ｐ△≧m1については、写真文字の中
間の性質を持つ領域であると判定して(iii)の場合よ
り階調再現数を少なくさせ分解能を上げる処理を
行う。たとえば、第４図ａ，ｂに示すように閾値
を中間レベルに多くして、黒または白に近いレベ
ルを２値化するような閾値マトリツクスを用いて
２値化する。なお、濃淡画像領域中で、２値画像
領域と判定する部分もあるが、この部分は濃度変
化の大きい部分であるため、階調再現数はあまり
重要でなく、画質にはあまり影響しない。２値画
像領域中で濃淡画像領域と判定する部分について
も同様である。 For m 2 >P△≧m 1 in (ii), it is determined that the area has properties intermediate to those of photographic characters, and processing is performed to increase the resolution by reducing the number of tone reproductions compared to the case (iii). For example, as shown in FIGS. 4a and 4b, the threshold value is increased to an intermediate level, and a threshold value matrix that binarizes a level close to black or white is used to perform binarization. Note that there is a portion of the grayscale image area that is determined to be a binary image area, but since this portion is a portion where density changes are large, the number of tone reproductions is not very important and does not affect the image quality much. The same applies to the portion of the binary image area that is determined to be a grayscale image area.
１例として、m1＝３、m2＝６、ｈ＝６に設定
し、第１図に対して本方式の処理を行つた場合、
ブロツク４、８は文字画像領域、ブロツク３、
５、６、７は中間領域、ブロツク１、２は濃淡領
域となる。この場合、ブロツク４、８は閾値ｈ＝
６として単純２値化、ブロツク３、５、６、７を
第４図ｂの閾値を用いて２値化、ブロツク１、２
は第２図の閾値を用いて２値化したものを第５図
に示す。 As an example, when setting m 1 = 3, m 2 = 6, and h = 6, and performing the processing of this method on Fig. 1,
Blocks 4 and 8 are character image areas, block 3,
Blocks 5, 6, and 7 are intermediate areas, and blocks 1 and 2 are gray areas. In this case, blocks 4 and 8 have a threshold h=
Blocks 3, 5, 6, and 7 are binarized using the threshold shown in Figure 4b, and blocks 1 and 2 are simply binarized as 6.
is binarized using the threshold shown in FIG. 2 and is shown in FIG.
上述の説明では、17階調再現の場合について説
明したが、18階調以上を再現する場合には、閾値
マトリツクスのサイズを大きくし閾値のレベル数
を多くすることによつてできる。例えば、８×８
閾値マトリツクスを用いれば65階調を再現でき
る。 In the above description, the case of reproduction of 17 gradations has been explained, but reproduction of 18 or more gradations can be achieved by increasing the size of the threshold value matrix and increasing the number of threshold levels. For example, 8×8
Using a threshold matrix, 65 gradations can be reproduced.
また、第３図の４×４の閾値配置以外にも、第
６図のａ，ｂ，ｃ，ｄに１例を示すような各種の
閾値配置を用いることができる。各領域の処理方
式としては上述の組織的２値デイザ法だけでな
く、たとえばブロツク内の平均濃度レベルを求
め、それに対応した黒画素の数を決め、黒画素の
配置をブロツク内の画信号レベルの大きい順に配
置する方法など各種の擬似中間調再現法を用いる
ことができる。また、記録装置が多値記録可能な
場合には、領域内の処理方式は、各画素に対して
画信号に対応した中間調濃度を再現する通常の多
値記録方式のものであつてもよい。 Further, in addition to the 4×4 threshold arrangement shown in FIG. 3, various threshold arrangement can be used, examples of which are shown in a, b, c, and d of FIG. As a processing method for each area, in addition to the systematic binary dither method described above, for example, the average density level within a block is determined, the corresponding number of black pixels is determined, and the arrangement of black pixels is determined based on the image signal level within the block. Various pseudo-halftone reproduction methods can be used, such as a method of arranging the pixels in descending order of . Further, if the recording device is capable of multi-value recording, the processing method within the area may be a normal multi-value recording method that reproduces a halftone density corresponding to the image signal for each pixel. .
さらに、画素単位ごとに数階調の中間調を再現
させ、組織的２値デイザ法を応用した多値デイザ
法を用いることもできる。この方法の具体例とし
て、画素単位ごとに３階調を再現でき、閾値マト
リツクスを２×２として９階調再現できる場合に
ついて述べる。第７図は、２×２閾値マトリツク
スを示している。画信号が０〜４のときａの閾値
マトリツクスを用い、画信号が閾値より小さい場
合には白、閾値以上の場合には中間調として記録
し、また画信号が５〜８のときｂの閾値マトリツ
クスを用い、画信号が閾値より小さい場合には中
間調、閾値以上の場合には黒で記録する。 Furthermore, it is also possible to use a multilevel dither method, which is an application of the systematic binary dither method, in which several halftones are reproduced for each pixel. As a specific example of this method, a case will be described in which three gradations can be reproduced for each pixel, and nine gradations can be reproduced with a 2×2 threshold matrix. FIG. 7 shows a 2×2 threshold matrix. When the image signal is 0 to 4, the threshold matrix of a is used, when the image signal is smaller than the threshold, it is recorded as white, and when it is above the threshold, it is recorded as halftone, and when the image signal is 5 to 8, the threshold of b is used. Using a matrix, when the image signal is smaller than a threshold value, it is recorded in half tone, and when it is above the threshold value, it is recorded in black.
なお、２値デイザ法の閾値マトリツクス中の閾
値の小さい所は黒になりやすいので、文字部分で
濃淡領域と判定したとき、本来白であつた所が黒
となるため画質劣化をきたすことがあり、これを
改善するためにブロツク内の平均濃度があらかじ
め定められた値ｑより小さい場合、ブロツク内の
全画素を白としてもよい。たとえば、画信号を０
〜16、ｑ＝0.75、ブロツクの大きさを４×４マト
リツクスとする。 Note that areas with small thresholds in the threshold matrix of the binary dither method tend to turn black, so when a text area is determined to be a dark and light area, areas that were originally white turn black, which can cause deterioration in image quality. To improve this, if the average density within the block is smaller than a predetermined value q, all pixels within the block may be made white. For example, set the image signal to 0
~16, q=0.75, and the block size is a 4×4 matrix.
第８図において、ｂはａの画信号について、
m1＝４、m2＝７、ｋ＝６として第５図の場合と
同様な処理で２値化したものである。ｃは、ｑ＝
0.75に設定したもので、最初にブロツク内の平均
濃度を求め、前記平均濃度が0.75より小さいブロ
ツクについては、ブロツク内のすべての画素を白
とし、前記平均濃度が0.75以上のブロツクについ
ては、ｂで行つた同じ処理を用いてａの画信号を
２値化したものである。ｃは、ｂに比べ白黒の凹
凸が少なくなつている。 In FIG. 8, b is for the image signal of a,
It is binarized using the same process as in FIG. 5, with m 1 =4, m 2 =7, and k=6. c is q=
0.75, the average density within the block is first determined, and for blocks where the average density is less than 0.75, all pixels within the block are set to white, and for blocks where the average density is 0.75 or more, b The image signal of a is binarized using the same processing performed in . In c, there are fewer irregularities in black and white than in b.
上記の例においては３領域に分類したが、中間
領域を含まない２領域あるいは４領域以上に分離
してもよい。たとえば、４領域分離で１ブロツク
の構成が４画素×４画素で17階調を表わす場合、
０≦m1≦m2≦m3≦16で、16≧Ｐ△＞m3につい
ては、第９図のａに示すような一つの閾値マトリ
ツクス、m3≧Ｐ△＞m2については、閾値がせま
い範囲で分布するｂの閾値マトリツクス、m2≧
Ｐ△＞m1については、閾値が若干広い範囲で分
布するｃの閾値マトリツクス、m1≧Ｐ△につい
ては、16の閾値を持つｄの閾値マトリツクス、を
用いるというようにして、ｍが小さいほど階調再
現数を多く、ｍが小さいほど一定の閾値に近づく
ようにすれば良い。ブロツク構成が８画素×８画
素で64階調を表わすような場合についても、同様
に上記の考え方に基づいた任意の閾値マトリツク
スを用いることができる。 In the above example, the area is classified into three areas, but it may be separated into two areas not including the intermediate area, or into four or more areas. For example, if one block is composed of 4 pixels x 4 pixels and represents 17 gradations in 4-area separation,
0≦m 1 ≦m 2 ≦m 3 ≦16, and for 16≧P△>m 3 , one threshold value matrix as shown in a of FIG. 9 is used, and for m 3 ≧P△>m 2 , one threshold value matrix threshold matrix of b distributed in a narrow range, m 2 ≧
For P△>m 1 , a threshold matrix of c whose threshold values are distributed over a slightly wider range is used, and for m 1 ≧P△, a threshold matrix of d with 16 thresholds is used. The number of gradation reproductions may be increased, and the smaller m is, the closer it is to a certain threshold value. Even in the case where the block configuration is 8 pixels x 8 pixels and represents 64 gradations, any threshold value matrix based on the above idea can be similarly used.
また、領域を決める基準となるブロツクの大き
さと閾値マトリツクスの大きさとを同じにした
が、必ずしも同じ大きさにする必要はない。たと
えば、第１０図は33階調再現の場合の閾値配列を
示したものであるが、ブロツク構成は実線で囲ま
れた４×４として、濃淡画像領域と判定された場
合に、各ブロツクの位置によりブロツクに対応す
る閾値マトリツクスのとり方をＡまたはＢとして
もよい。 Furthermore, although the size of the block and the size of the threshold matrix, which serve as a criterion for determining the area, are made the same, they do not necessarily have to be the same size. For example, Figure 10 shows the threshold array for 33-level reproduction.The block configuration is 4x4 surrounded by solid lines, and when it is determined that it is a grayscale image area, the position of each block is Accordingly, the threshold value matrix corresponding to the block may be set to A or B.
第１１図は、本発明により17階調再現の場合、
３種類の閾値マトリツクスを用いて２値化処理を
行うための回路構成の１例を示すブロツク図であ
る。 FIG. 11 shows that in the case of 17 gradation reproduction according to the present invention,
FIG. 2 is a block diagram showing an example of a circuit configuration for performing binarization processing using three types of threshold matrices.
第１１図において、１，２は画像メモリ、３は
ブロツクメモリ、４は像域判定回路、５は閾値メ
モリ切換回路、６は濃淡画像用の閾値マトリツク
スメモリ、７は中間領域用の閾値マトリツクスメ
モリ、８は文字領域用の閾値マトリツクスメモ
リ、９は２値化回路である。 In FIG. 11, 1 and 2 are image memories, 3 is a block memory, 4 is an image area determination circuit, 5 is a threshold value memory switching circuit, 6 is a threshold value matrix memory for grayscale images, and 7 is a threshold value matrix for intermediate areas. 8 is a threshold matrix memory for character areas, and 9 is a binarization circuit.
動作を説明すると、まず原稿から読みとつた画
情報は、画像メモリ１に記憶される。４走査線の
画情報が記憶された後、スイツチ１０はａ側から
ｂ側に切りかわり、同時にスイツチ１１がｂから
ａに切りかわり、次の画情報を画像メモリ２に記
憶しながら、画像メモリ１の内容は１ブロツク単
位ずつブロツクメモリ３に転送される。像域判定
回路４は、ブロツクメモリ３の内容から、ブロツ
ク内の各画素のうち濃度レベルが最大のものと最
小のものとを検出し、それらの濃度レベル差を求
め、あらかじめ設定された値m1、m2と比較し
て、ブロツク内の画情報を濃淡画像、中間画像、
２値画像のいずれかに判定する。その結果にもと
づき、閾値メモリ切り換え回路５は、閾値の多い
濃淡画像用の４×４閾値マトリツクスメモリ６、
中間領域用の閾値を持つ４×４閾値マトリツクス
メモリ７、あるいは一定の閾値を持つ４×４閾値
マトリツクスメモリ８のいずれかを選択する。 To explain the operation, first, image information read from a document is stored in the image memory 1. After the image information of four scanning lines has been stored, the switch 10 is switched from the a side to the b side, and at the same time the switch 11 is switched from b to a, and while the next image information is stored in the image memory 2, The contents of 1 are transferred to the block memory 3 one block at a time. The image area determination circuit 4 detects, from the contents of the block memory 3, the maximum and minimum density levels of each pixel in the block, calculates the difference in density levels, and sets a preset value m. 1 , m2 , the image information in the block is divided into grayscale images, intermediate images,
It is determined whether the image is a binary image. Based on the results, the threshold memory switching circuit 5 stores a 4×4 threshold matrix memory 6 for grayscale images with many thresholds,
Either the 4×4 threshold matrix memory 7 having a threshold value for the intermediate region or the 4×4 threshold matrix memory 8 having a constant threshold value is selected.
このようにして選択された閾値マトリツクスメ
モリ６，７，８のいずれかの内容とブロツクメモ
リ３の濃度レベルを２値化回路９により比較し
て、画信号レベルが所定の閾値レベルより大きい
場合を黒、小さい場合を白とすることにより２値
信号をとり出す。ブロツクメモリ３の画信号が処
理されると画像メモリ１から次の１ブロツクの画
情報をブロツクメモリ３に転送し、以下同様の処
理で２値化処理を行う。画像メモリ１の内容がす
べて処理され、画像メモリ２に次の４走査線の画
情報が記憶されると、スイツチ１０はｂ側からａ
側に、スイツチ１１はａ側からｂ側に切りかわ
り、画像メモリ２の内容が上述の手順で処理され
る。 The binarization circuit 9 compares the content of any of the threshold matrix memories 6, 7, and 8 selected in this way with the density level of the block memory 3, and if the image signal level is greater than a predetermined threshold level, A binary signal is extracted by setting the value to black and the smaller value to white. When the image signal in the block memory 3 is processed, the image information of the next block is transferred from the image memory 1 to the block memory 3, and thereafter binarization processing is performed in the same manner. When all the contents of the image memory 1 have been processed and the image information of the next four scanning lines has been stored in the image memory 2, the switch 10 switches from side b to side a.
On the other hand, the switch 11 is switched from the a side to the b side, and the contents of the image memory 2 are processed in the above-described procedure.
以上説明したように、本発明の方法によれば、
ブロツク単位に高階調再現を優先する部分と高分
解能を優先する部分、さらにこれらの中間調の領
域を再現する部分、に区別するので、写真画像や
文字画像が混在する原稿を良好に再現することが
できる利点がある。 As explained above, according to the method of the present invention,
It distinguishes between blocks that give priority to high gradation reproduction, parts that give priority to high resolution, and parts that reproduce these halftone areas, so it is possible to reproduce originals that contain a mixture of photographic images and text images. It has the advantage of being able to
したがつて、本発明法をフアクシミリ等で中間
調情報電送のための処理方法として適用すれば有
用である。 Therefore, it is useful if the method of the present invention is applied as a processing method for transmitting halftone information by facsimile or the like.
第１図は本発明の実施例を示すための画像例の
構成図、第２図は従来の組織的デイザ法による閾
値マトリツクスの１例の構成図、第３図は第２図
の閾値マトリツクスを用いて２値化した画像の構
成図、第４図ａ，ｂおよび第６図ａ乃至ｄは組織
的２値デイザ法による２値化処理を行うための閾
値マトリツクス例の構成図、第５図は本発明方法
による２値化処理例を示す構成図、第７図ａ，ｂ
は多値デイザ用閾値マトリツクスの１例を示す構
成図、第８図ａ乃至ｃは実施例を説明するための
画像処理説明図、第９図ａ乃至ｄは２値化処理を
行うための閾値マトリツクス例の構成図、第１０
図は４×８閾値マトリツクスとブロツクの大きさ
の１例を示す構成図、第１１図は本発明方法によ
る中間処理回路例を示すブロツク図である。
図中、１，２は画像メモリ、３はブロツクメモ
リ、４は像域判定回路、５は閾値メモリ切換回
路、６，７，８は閾値マトリツクス・メモリ、９
は２値化回路を示す。
FIG. 1 is a block diagram of an example image for showing an embodiment of the present invention, FIG. 2 is a block diagram of an example of a threshold matrix based on the conventional organized dither method, and FIG. 3 is a block diagram of an example of a threshold matrix shown in FIG. Figures 4a, b and 6a to d are diagrams of an example of a threshold matrix for performing binarization processing using the systematic binary dither method. are block diagrams showing an example of binarization processing according to the method of the present invention, FIGS. 7a and b
8 is a configuration diagram showing an example of a threshold value matrix for multilevel dithering, FIGS. 8a to 8c are image processing explanatory diagrams for explaining the embodiment, and FIGS. 9a to d are threshold values for performing binarization processing. Configuration diagram of matrix example, No. 10
This figure is a block diagram showing an example of a 4.times.8 threshold matrix and block size, and FIG. 11 is a block diagram showing an example of an intermediate processing circuit according to the method of the present invention. In the figure, 1 and 2 are image memories, 3 is a block memory, 4 is an image area determination circuit, 5 is a threshold value memory switching circuit, 6, 7, and 8 are threshold value matrix memories, 9
indicates a binarization circuit.
Claims (1)
し、ブロツク毎に複数の閾値マトリツクスを用意
してそのうちの１つの閾値マトリツクスを選択す
る中間調信号処理方式において、各ブロツク内で
濃度レベルが最大の画素と濃度レベルが最小の画
素との濃度レベル差を求め、前記濃度レベルの差
の値に応じて前記複数の閾値マトリツクスのうち
から１つの閾値マトリツクスを選択し、前記ブロ
ツク内の画信号を２値化することを特徴とする中
間調信号処理方式。 ２ 第１項記載の中間調信号処理方式において、
ブロツク内の平均濃度があらかじめ定められた値
より小さい場合、ブロツク内の全画素を白とする
ことを特徴とする中間調信号処理方式。[Claims] 1. In a halftone signal processing method in which a screen is divided into blocks each consisting of a plurality of pixels, a plurality of threshold matrices are prepared for each block, and one of the threshold matrices is selected. The density level difference between the pixel with the maximum density level and the pixel with the minimum density level is determined, one threshold matrix is selected from the plurality of threshold matrices according to the value of the difference in density level, and one threshold matrix is selected from among the plurality of threshold matrices, and A halftone signal processing method characterized by binarizing an image signal. 2 In the halftone signal processing method described in paragraph 1,
A halftone signal processing method characterized in that when the average density within a block is smaller than a predetermined value, all pixels within the block are rendered white.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56143418A JPS5844861A (en) | 1981-09-11 | 1981-09-11 | Processing system for intermediate tone signal |
| GB08218275A GB2103449B (en) | 1981-06-29 | 1982-06-24 | Method and apparatus for gray level signal processing |
| US06/392,155 US4547811A (en) | 1981-06-29 | 1982-06-25 | Method and apparatus for gray level signal processing |
| FR8211292A FR2508747B1 (en) | 1981-06-29 | 1982-06-28 | METHOD AND APPARATUS FOR DETERMINING AN IMAGE AREA AND FOR CORRECTING THIS DETERMINATION |
| DE3224319A DE3224319C2 (en) | 1981-06-29 | 1982-06-29 | Method and device for determining the type of density level distribution of an image area |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56143418A JPS5844861A (en) | 1981-09-11 | 1981-09-11 | Processing system for intermediate tone signal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5844861A JPS5844861A (en) | 1983-03-15 |
| JPS6336713B2 true JPS6336713B2 (en) | 1988-07-21 |
Family
ID=15338288
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP56143418A Granted JPS5844861A (en) | 1981-06-29 | 1981-09-11 | Processing system for intermediate tone signal |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5844861A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59205876A (en) * | 1983-05-10 | 1984-11-21 | Canon Inc | Method and apparatus for processing color picture |
| JPS60102060A (en) * | 1983-11-09 | 1985-06-06 | Hitachi Ltd | Picture binary-coding device |
| JPS60232779A (en) * | 1984-05-02 | 1985-11-19 | Ricoh Co Ltd | Binary-coding device of picture signal |
| JPH0640661B2 (en) * | 1985-01-08 | 1994-05-25 | 富士ゼロックス株式会社 | Image processing device |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5393835A (en) * | 1977-01-28 | 1978-08-17 | Ricoh Co Ltd | Copy picture quality controller of electrostatic copying machine |
| JPS5476007A (en) * | 1977-11-30 | 1979-06-18 | Ricoh Co Ltd | Picture reproducing system |
| US4196453A (en) * | 1978-12-01 | 1980-04-01 | Xerox Corporation | Image screening system |
| JPS5580958A (en) * | 1978-12-15 | 1980-06-18 | Toshiba Corp | Picture signal binary coding system |
| JPS5666970A (en) * | 1979-11-06 | 1981-06-05 | Toshiba Corp | Binary device of variable density type picture |
-
1981
- 1981-09-11 JP JP56143418A patent/JPS5844861A/en active Granted
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5393835A (en) * | 1977-01-28 | 1978-08-17 | Ricoh Co Ltd | Copy picture quality controller of electrostatic copying machine |
| JPS5476007A (en) * | 1977-11-30 | 1979-06-18 | Ricoh Co Ltd | Picture reproducing system |
| US4196453A (en) * | 1978-12-01 | 1980-04-01 | Xerox Corporation | Image screening system |
| JPS5580958A (en) * | 1978-12-15 | 1980-06-18 | Toshiba Corp | Picture signal binary coding system |
| JPS5666970A (en) * | 1979-11-06 | 1981-06-05 | Toshiba Corp | Binary device of variable density type picture |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5844861A (en) | 1983-03-15 |
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