JP4428743B2 - Image processing method and apparatus, printer, image processing system, and storage medium - Google Patents

Description

【００５７】
そして、「Vectorでモノクロ」の場合には、上述したようなＵＣＲ処理をかけて色ずれを防ぎ、「Bitmapでカラー」の場合には、ＫをできるだけのせないようにＵＣＲ処理を止めることで彩度の高い高品質な画像の実現ができる。なお、このような色処理の使い分けは、上述の図１１のフローチャートにおけるステップＳ２３において、ＲＧＢデータからＹＭＣＫデータへの変換処理をステップＳ２２で読み取った属性情報に従って切り換えることで行なわれる。
【００５８】
ここで重要なのは、属性マップは、階層的に情報をもつことにより、機能が限定された安価なプリンタから機能を豊富にもつ高付加価値なプリンタまでに対応することが可能であるということである。たとえば、属性マップのｂｉｔ数を１から２へと増やすことにより第１の実施形態と第２の実施形態のどちらも実施できるようになる。そして、第２の実施形態のように２ビットを用いれば、すなわちビット数を増やせば、よりきめの細かい画像処理の切り替えが可能となり、より高品質な画像を提供することが可能になる。
【００５９】
したがって、機能の限定された安価なプリンタでは属性情報の下位のｂｉｔのみを用いて処理を行い、より機能の多いプリンタでは属性情報のより多くのｂｉｔを用いた高度な処理を行うことが可能である。このように、基本的に下位ビットにより用いられる頻度が多い属性情報をもつように構成し、０ｂｉｔ目から順に階層的に情報をもつことで、同じ属性マップの構造をもちながらも、システムのもつ特性（コスト重視、画質重視など）に応じてより適切な構成を構築することができる。
【００６０】
［第３の実施形態］
第２の実施形態では、属性情報の複数のビットの各々が互いに独立している場合を説明したが、属性情報の複数ビットが互いに関連しあっていてもよい。第３の実施形態では、属性情報の複数のビットが互いに主従関係にある場合を説明する。
【００６１】
図１３は第３の実施形態による属性情報のデータフォーマットの１例を示す図である。この属性情報は、０ｂｉｔ目、１ｂｉｔ目、２ｂｉｔ目の３ｂｉｔ情報をもつ。０ｂｉｔ目は、Bitmapフラグであり、上記第１及び第２の実施形態と同様に、１ならBitmapオブジェクトから生成された画素、０ならvectorオブジェクトから生成された画素、つまり、文字またはグラフィック画像を示す。
【００６２】
また、１ｂｉｔ目は色フラグであり、上記第２の実施形態と同様に、１なら色（カラー）、０なら白黒（色情報をもたない白、グレイ、黒）を示す。
【００６３】
２ｂｉｔ目は、文字フラグであり、０なら文字以外、１なら文字オブジェクトであることを表す。
【００６４】
属性マップの２ｂｉｔ目までの情報を用いると以下のようなことが可能になる。たとえば、図１６において、ＴＥＸＴ１１６の色をＲ＝Ｇ＝Ｂ＝０の黒色として定義してあった場合、これに対する最適なＣＭＹＫ信号は８ビットの濃度信号で表すとＣ＝Ｍ＝Ｙ＝０、かつＫ＝２５５となる。つまり黒い文字はプリンタの４色のトナーのうち黒トナーのみで再現するのが好ましい。
【００６５】
一方、自然画像１１４の特定ピクセルの画素値がＲ＝Ｇ＝Ｂ＝０であった場合、これを上記文字データと同様にＣ＝Ｍ＝Ｙ＝０、かつＫ＝２５５に変換してしまうと、本来、自然画像中のもっとも濃度の高い部分を表現すべきなのが黒トナーのみで再現されるため、絶対濃度が不足してしまう。従って、この場合はＣ＝Ｍ＝Ｙ＝１００、Ｋ＝２５５といった値に変換して絶対濃度を高くした方が好ましい結果が得られる。
【００６６】
また、グラフィック画像１１５は、文字と自然画像の中間の値、すなわちＲ＝Ｇ＝Ｂ＝０であった場合、Ｃ＝Ｍ＝Ｙ＝５０、Ｋ＝２５５が最適だと仮定する。この場合も、画像メモリから転送される多値のビットマップイメージに対し像域分離処理をおこなって、上述のような色処理（Ｒ＝Ｇ＝Ｂ＝０に対する色処理）を適応的に切り替えるという方法も考えられるが、前述と同様の不具合（像域分離手法というものが文字領域を１００％検出できるとは限らず、また自然画像領域の中にも誤って文字領域として検出してしまう場合もあるため、信頼性に欠ける）を防止することはできない。
【００６７】
これに対して、第３の実施形態の属性マップ情報を用いれば、文字画像１１６は属性マップの０ｂｉｔ目が１でかつ２ｂｉｔ目が１の画素で構成され、グラフィック画像１１５は属性マップの０ｂｉｔ目が１でかつ２ｂｉｔ目が０の画素で構成され、自然画像１１４（Bitmap）は属性マップの０ｂｉｔ目が０の画素で構成される。このため、画素毎に、自然画像、文字画像、グラフィックの切り分けが簡単にできる。そのため、上記のように、文字画像部は、Ｒ＝Ｇ＝Ｂ＝０であった場合、Ｃ＝Ｍ＝Ｙ＝０、Ｋ＝２５５とし、グラフィック画像部は、Ｒ＝Ｇ＝Ｂ＝０であった場合、Ｃ＝Ｍ＝Ｙ＝５０、Ｋ＝２５５とし、自然画像部は、Ｒ＝Ｇ＝Ｂ＝０であった場合、Ｃ＝Ｍ＝Ｙ＝１００、Ｋ＝２５５とすることが簡単かつ正確に実現可能となり、よりよい画像品質を実現できる。なお、上述の黒色に対する処理は、図１１のステップＳ２２において読み取られた属性情報に基づいて、ステップＳ２３における色処理を切り換えるようにすれば実現できる。
【００６８】
以上のように、複数のｂｉｔを組み合わせて、より細かい属性を持たせることができる。
【００６９】
なお、第３の実施形態と第２の実施形態との違いは、以下のとおりである。
【００７０】
０ｂｉｔ目と１ｂｉｔ目の情報はそれぞれ独立しており、０ｂｉｔ目、１ｂｉｔ目単独で用いることが可能な情報であるのに対して、２ｂｉｔ目の情報は、０ｂｉｔ目の情報との組み合わせで用いることになる。今回は、０ｂｉｔ目と２ｂｉｔ目の２ｂｉｔを用いたため、２の２乗で４通りの属性を持たせることができる。３ｂｉｔ分の組み合わせであれば８通り、４ｂｉｔ分の組み合わせであれば１６通りの属性を持たせることが可能である。
【００７１】
下記に示した通り、０ｂｉｔ目、２ｂｉｔ目がともに１である場合は下地（何もオブジェクトの情報のない状態）を指定している。オブジェクト情報は３つ（自然画像、文字画像、グラフィック）であるのに、２ｂｉｔ分の４通りの情報が持てるため、全く異なる属性を持たせることが可能である例である。Bitmapで文字という属性は矛盾しているが、２ｂｉｔ目は独立して用いることの可能な情報ではなく、０ｂｉｔ目の情報により意味あいが違う従属の情報として用いるように扱う。
【００７２】

【００７３】
第３の実施形態では複数ｂｉｔの組み合わせによる属性マップについて述べてきた。０ｂｉｔ目が独立した情報でありながら、２ｂｉｔ目は０ｂｉｔ目に従属した属性で、２つのｂｉｔを組み合わせて用い、複数ｂｉｔを組み合わせた属性とする。
【００７４】
なお、複数ｂｉｔの組み合わせによる属性は、独立した属性がなく、組み合わせなければ意味をなさないようにも構成することも可能である。例えば、図１４のように、０ｂｉｔ目、１ｂｉｔ目の構成で、

のように属性情報を構成することも可能である。いずれの場合も、下地の属性である画素では処理を省略することで処理速度を上げることが可能となる。
【００７５】
なお、本発明は、複数の機器（例えばホストコンピュータ，インタフェイス機器，リーダ，プリンタなど）から構成されるシステムに適用しても、一つの機器からなる装置に適用してもよい。
【００７６】
また、本発明の目的は、前述した実施形態の機能を実現するソフトウェアのプログラムコードを記録した記憶媒体を、システムあるいは装置に供給し、そのシステムあるいは装置のコンピュータ（またはＣＰＵやＭＰＵ）が記憶媒体に格納されたプログラムコードを読出し実行することによっても、達成されることは言うまでもない。
【００７７】
この場合、記憶媒体から読出されたプログラムコード自体が前述した実施形態の機能を実現することになり、そのプログラムコードを記憶した記憶媒体は本発明を構成することになる。
【００７８】
プログラムコードを供給するための記憶媒体としては、例えば、フロッピディスク，ハードディスク，光ディスク，光磁気ディスク，ＣＤ−ＲＯＭ，ＣＤ−Ｒ，磁気テープ，不揮発性のメモリカード，ＲＯＭなどを用いることができる。
【００７９】
また、コンピュータが読出したプログラムコードを実行することにより、前述した実施形態の機能が実現されるだけでなく、そのプログラムコードの指示に基づき、コンピュータ上で稼働しているＯＳ（オペレーティングシステム）などが実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【００８０】
さらに、記憶媒体から読出されたプログラムコードが、コンピュータに挿入された機能拡張ボードやコンピュータに接続された機能拡張ユニットに備わるメモリに書込まれた後、そのプログラムコードの指示に基づき、その機能拡張ボードや機能拡張ユニットに備わるＣＰＵなどが実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【００８１】
【発明の効果】
以上説明したように、本発明によれば、画像データをプリント出力するに際して、画像データに含まれる各画像の属性に応じた適切なデータ処理が実現され、出力画像の品位が向上する。
【図面の簡単な説明】
【図１】本実施形態による画像処理システムの構成を表すブロック図である。
【図２】第１の実施形態による属性情報のデータフォーマットの１例を示す図である。
【図３】各画素に対応づけられた属性マップ情報の１例を示す図である。
【図４】画像データと属性マップ情報を同じ記憶媒体に記憶する場合の属性マップの格納方法の例を説明する図である。
【図５】画像データと属性マップ情報を同じ記憶媒体に記憶する場合の属性マップの格納方法の別の例を説明する図である。
【図６】画像データと属性マップ情報を同じ記憶媒体に記憶する場合の属性マップの格納方法の別の例を説明する図である。
【図７】画像データと属性マップ情報を同じ記憶媒体に記憶する場合の属性マップの格納方法の別の例を説明する図である。
【図８】３ｘ３のサイズのディザマトリックスの一例を示す図である。
【図９】８ｘ８のサイズのディザマトリックスの一例を示す図である。
【図１０】本実施形態によるオブジェクトの描画及び属性マップの生成を説明するフローチャートである。
【図１１】画像処理部１７によるＣＭＹＫデータの生成手順を説明するフローチャートである。
【図１２】第２の実施形態による属性情報のデータフォーマットの１例を示す図である。
【図１３】第３の実施形態による属性情報のデータフォーマットの１例を示す図である。
【図１４】第３の実施形態による属性情報のデータフォーマットの他の例を示す図である。
【図１５】ホストコンピュータデ作成した文書をプリンタなどにより出力するシステムの一般的な概略構成を示す図である。
【図１６】自然画像、文字画像、グラフィックスの３つの画像形態を説明する図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing method and apparatus, a printer including the image processing apparatus, and an image processing system.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an image processing system that digitally generates image data and prints it out is known. Such a system is generally as shown in FIG. FIG. 15 is a diagram illustrating a schematic configuration of a system that creates a page layout document, a word processor, a graphic document, and the like by performing DTP using the host computer 101 and outputs a hard copy by a laser beam printer, an inkjet printer, or the like. .
[0003]
In FIG. 15, reference numeral 102 denotes an application that runs on the host computer. Typical examples of the application 102 include word processing software such as Microsoft Word (R) and page layout software such as Adobe PageMaker (R). Digital documents created with these software are transferred to the printer driver 103 via an operating system (OS) of a computer (not shown).
[0004]
The above-described digital document is usually represented as a set of command data representing graphics, characters, etc. constituting one page, and these commands are sent to the printer driver 103. A series of commands constituting the screen is expressed in a language system called PDL (page description language). Typical examples of such PDL include GDI (R) and PS (R) (postscript).
[0005]
The printer driver 103 transfers the received PDL command to the rasterizer 105 in the raster image processor 104. The rasterizer 105 expands characters, graphics, and the like expressed by PDL commands into a two-dimensional bitmap image for actual printer output. Since a bitmap image is an image that fills a two-dimensional plane as a one-dimensional raster (line) repetition, 105 is called a rasterizer. The developed bitmap image is temporarily stored in the image memory 106.
[0006]
FIG. 16 schematically shows the above operation. The document image 111 displayed on the host computer is sent as a PDL command string 112 to the rasterizer via the printer driver, and the rasterizer develops a two-dimensional bitmap image on the image memory 106 as shown at 113. The developed image data is sent to the color printer 107. The color printer 107 is provided with an image forming unit 108 of a well-known electrophotographic system or ink jet recording system, and a visible image is formed on a sheet by these and printed out. Note that the image data in the image memory 106 is transferred in synchronization with a not-shown synchronization signal or clock signal necessary for operating the image forming unit 108 or a transfer request for a specific color component signal. It is.
[0007]
[Problems to be solved by the invention]
In the conventional example as described above, it is clear that various problems occur with respect to the image forming unit 108 used for output.
[0008]
For example, a color printer normally uses a four-color toner or ink of cyan (C), magenta (M), yellow (Y), and black (K), based on the so-called subtractive color mixing principle. Is formed. On the other hand, when an application of a host computer displays an image, it is normal to use a color monitor, and the color monitor uses three additive primary colors of red (R), green (G), and blue (B). Display the color. Therefore, the colors of characters, figures, images, etc. constituting the document, which are read and laid out by the scanner, are all expressed as colors in which R, G, and B are mixed at a certain ratio. In other words, the rasterizer is defined as R, G, B as PDL and converts the color information transferred from the host computer into C, M, Y, K by some means, then generates a bitmap image and sends it to the printer. There is a need.
[0009]
However, the method of converting RGB to CMYK is not uniquely determined, and the optimum conversion method differs depending on the attribute of the graphic defined by PDL. For example, referring to the example of FIG. 16, the portion 114 is a natural image read by a scanner or the like, 115 is an electronically generated graphic image such as a circle or rectangle, and 116 is a character (TEXT) image. Has attributes.
[0010]
Here, if the TEXT color of the character image 116 is defined as black with R = G = B = 0, the optimal CMYK signal for this is expressed as an 8-bit density signal, C = M = Y = 0, And K = 255. That is, it is preferable to reproduce black characters using only black toner among the four colors of toner of the printer. On the other hand, if the pixel value of the specific pixel 114 of the natural image 114 is R = G = B = 0, and converted to C = M = Y = 0 and K = 255 as in the character data, Originally, what should express the highest density portion in a natural image is reproduced with only black toner, so that the absolute density is insufficient. Therefore, in this case, it is preferable that the absolute density is increased by converting into values such as C = M = Y = 100 and K = 255.
[0011]
As another example, there may be a case where the image forming unit can reproduce only binary dots. In this case, the rasterizer develops a multi-value bitmap image of Y, M, C, and K in the image memory, and the image forming unit that receives the raster image is a well-known binarization process such as an error diffusion method or a dither process. And the multi-value image signal is converted into a binary image signal and then printed out. At this time, the optimum binarization method changes depending on the attribute of the image.
[0012]
In other words, graphics such as characters and figures are preferably binarized by reducing the dither matrix size and emphasizing resolution. For natural images such as photographs, it is better to increase the matrix size and emphasize tone reproducibility. preferable.
[0013]
As described above, the optimum development processing by the rasterizer differs depending on the data attribute of the object, and if the rasterization is performed by a single processing method, the image quality is deteriorated.
[0014]
The present invention has been made in view of the above-described problems. When image data is printed out, appropriate data processing is realized according to the attribute of each image included in the image data, and the quality of the output image is improved. For the purpose.
[0015]
[Means for Solving the Problems]
  In order to achieve the above object, an image processing apparatus of the present invention comprises the following arrangement, for example. That is,
  Generating means for generating a bitmap image based on the input object data;
  Holding means for holding attribute information representing the attribute of the input object data in association with each pixel of the bitmap image generated by the generating means;
  Conversion means for converting the bitmap image generated by the generation means into data that can be processed by the image output unit;
  Switching means for switching processing contents in the conversion means based on attribute information held in the holding means.,
  The attribute information is composed of a plurality of bits, each of the plurality of attributes constituting the attribute information is assigned to each of the plurality of bits,
  Of a plurality of attributes assigned to each bit of the plurality of bits, an attribute that is frequently used by printers having different capabilities is assigned to lower bits of the plurality of bits.The
[0016]
  Moreover, the image processing method by this invention for achieving said objective is equipped with the following processes, for example. That is,
  A generation step of generating a bitmap image based on the input object data;
  A holding step for holding attribute information representing an attribute of the input object data in a memory in association with each pixel of the bitmap image generated in the generation step;
  A conversion step of converting the bitmap image generated in the generation step into data that can be processed by the image output unit;
  A switching step of switching processing contents in the conversion step based on the attribute information held in the holding step.,
  The attribute information is composed of a plurality of bits, each of the plurality of attributes constituting the attribute information is assigned to each of the plurality of bits,
  Of a plurality of attributes assigned to each bit of the plurality of bits, an attribute that is frequently used by printers having different capabilities is assigned to lower bits of the plurality of bits.The
[0017]
In addition, according to the present invention, a printer provided with the image processing apparatus is provided. Furthermore, according to the present invention, an image processing system including the image processing apparatus is provided. Furthermore, according to the present invention, there is provided a storage medium for storing a control program for causing a computer to realize the image processing method.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0019]
[First Embodiment]
FIG. 1 is a block diagram showing the configuration of the image processing system according to this embodiment.
[0020]
In FIG. 1, reference numeral 10 denotes a host computer. Reference numeral 11 denotes an application used in the host computer 10. Examples of the application 11 include word processing software, drawing software, graphic software, and the like. A printer driver 12 controls the interface with the printer when the application 11 outputs characters, graphics, and bitmap images to the printer.
[0021]
A raster image processor 13 expands the output through the printer driver into image data. The raster image processor 13 includes a rasterizer 14, an image memory 15 for storing image data, and an attribute map memory 16. The raster image processor may belong to the host computer side or the printer side.
[0022]
An image processing unit 17 converts image data stored in the image memory 15 with reference to information stored in the attribute map memory 16 and outputs image data (for example, each of YMCK images) that can be output by an image forming unit 19 described later. Binary image data). Reference numeral 18 denotes a color printer. The color printer 18 includes an image forming unit 19 for printing image data, which is electronic data, on a medium such as paper. The image forming unit 19 is an electrophotographic unit, an inkjet unit, or the like. A final output result is obtained through the image forming unit 19.
[0023]
In the present embodiment, the description will be given using the color printer 18 as a printer that performs print output. However, it is obvious that the processing of the present embodiment can be easily applied to a monochrome printer.
[0024]
Further, in the present embodiment, the image memory 15 and the attribute map memory 16 are represented by separate blocks for easy understanding, but the image data and the attribute map data can be read out to one storage medium. Of course it is also possible to memorize it.
[0025]
A digital document created by an application is expressed by a command system called PDL as described in the conventional example. The command is roughly composed of three objects. One is a character object, the second is a graphic object such as vector data such as a figure or a free curve, and the third is a Bitmap object such as image data obtained by reading a photograph or printed matter with a scanner or the like.
[0026]
For example, in the case of a character, the object consists of data such as a character code for identifying which character is a character, a font that defines the character shape, size information that indicates the size of the character, and color information that indicates the color of the character. As it is, the information cannot be interpreted by the image forming unit. Therefore, the printer driver 12 manages the interface with the printer, and plays a role such as synchronizing so that an appropriate image can be output by the image forming unit 19 which is the final stage, and the character, graphic, bitmap, etc. Sends a command sequence representing the object.
[0027]
The rasterizer 13 converts the received command sequence into two-dimensional Bitmap data that can be properly interpreted by the image forming unit, and simultaneously outputs an attribute map. The attribute map is two-dimensional information in which attribute information of each pixel is provided for each pixel. This attribute map is stored in the attribute map memory 16 so that each pixel can be associated with the two-dimensional image data and the attribute map.
[0028]
FIG. 2 is a diagram illustrating an example of a data format of attribute information. In this embodiment, 1-bit information having only the 0th bit is included, and the 0th bit represents a Bitmap flag. If the 0th bit is 1, it indicates a pixel generated from a Bitmap object, and if it is 0, it indicates a pixel generated from a vector object, that is, a character or graphic image.
[0029]
When the rasterizer 13 converts the object into two-dimensional bitmap data, the rasterizer 13 determines for each pixel whether the object is generated from a character, graphic, or natural image, and stores the two-dimensional image data in the attribute map memory 16. Attribute information is stored so that it can be associated with.
[0030]
FIG. 3 is a diagram illustrating an example of attribute map information associated with each pixel. FIG. 3 shows an image in which the number “1”, which is a character object, is superimposed on a bitmap object. When converting to a two-dimensional bitmap, attribute map information as shown in FIG. 3 is generated according to the format described in FIG. That is, “0” is output if the pixel is generated as a vector (character or graphic object) for each pixel, and “1” is output if the pixel is a bitmap object, and the attribute map as shown in FIG. Will be stored.
[0031]
Note that the attribute map may be configured in any way as long as it is stored so as to be associated with each pixel. The method of generating attribute information as an attribute map plane as shown in FIG. 3, storing image data in the image memory 15, and storing attribute map information in the attribute map memory 16 is an example, and other forms are adopted. May be.
[0032]
For example, if image data and attribute information are stored in the same storage medium, an attribute map plane may be added to each RGB plane as shown in FIG. Or when RGB data is comprised for every pixel like FIG. 5, you may embed in the form added to the RGB information of each pixel. Further, in order not to increase the amount of data, as shown in FIG. 6, the attribute information is embedded in the lower bits for each pixel of any one surface or a plurality of surfaces of the RGB planes. When RGB data is configured in one pixel as shown in FIG. 7, one or more lower-order bits of one or a plurality of color information among RED, GREEN, and BLUE information for each pixel. The attribute information may be embedded in the. In the example of FIG. 7, an example is shown in which an attribute map is embedded in the lower 3 bits of 8 bits of BLUE information (the attribute information is 1 bit in the first embodiment, but the second, third As will be described later in the embodiment, 2 bits and 3 bits can be used as attribute information).
[0033]
The image processing unit 17 extracts the attribute map information embedded as described above, and based on the image data stored in the image memory 15 and the attribute map associated with the image data for each pixel, The attribute is determined, the image processing is switched, and the optimum image processing is performed for each attribute of the image.
[0034]
The processing procedure of the present embodiment described above will be further described with reference to FIGS.
[0035]
FIG. 10 is a flowchart for explaining object drawing and attribute map generation according to this embodiment. First, in step S11, the rasterizer 14 analyzes the input object data. In step S 12, the image is developed into an RGB image and drawn in the image memory 15. In step S13, it is determined whether the attribute of the object is “natural image” or “graphic or character”.
[0036]
If it is determined in step S13 that the image is a natural image, the process proceeds to step S14, and the attribute map information is set to “1” and is written at a position corresponding to each pixel of the object on the attribute map memory 16 (step S16). . On the other hand, if it is determined in step S13 that the image is a graphic or a character, the attribute map information is set to “0” and written in the position corresponding to each pixel position of the object on the attribute map memory 16 (steps S15 and S16). ).
[0037]
In step S17, it is determined whether there is a next object to be drawn. If it exists, the process returns to step S11, and if it does not exist, the present process is terminated.
[0038]
FIG. 11 is a flowchart for explaining a procedure for generating CMYK data by the image processing unit 17.
[0039]
First, in step S21, image data is read from the image memory 15 in units of pixels. In the present embodiment, RGB multi-value data is stored in the image memory 15. In step S22, the pixel attribute information read in step S21 is read from the attribute map memory 16. Although various variations of the attribute information storage form are shown in FIGS. 5 to 7, in step S22, the attribute information of the corresponding pixel may be read in accordance with each form.
[0040]
In step S23, RGB multilevel data is converted to YMCK multilevel data. Then, by the processing of steps S24 to S26, the image forming unit 19 converts (binarizes) the data into binary data of each color of YMCK that can be processed. In this binarization, a dither matrix is used in the present embodiment. At this time, a dither matrix is used depending on the attribute information of each pixel.
[0041]
First, in step S24, it is determined from the attribute information read in step S22 whether the attribute given to the pixel to be processed is “natural image” or “graphic or character”. If the attribute of the pixel to be processed is “graphic or character”, the process proceeds to step S25, and binarization is performed using a 3 × 3 dither matrix as shown in FIG. To do). On the other hand, if the attribute of the pixel to be processed is “natural image”, the process proceeds to step S26, and binarization is performed using an 8 × 8 dither matrix (gradation is emphasized).
[0042]
As described above, the following processing can be performed by using the attribute map information. Referring to the example of FIG. 16, the portion 114 has a different attribute such as a natural image read by a scanner or the like, 115 a graphic image generated electronically such as a circle or rectangle, and 116 a character (TEXT) image. ing. Here, consider a case where the image forming unit can reproduce only binary dots.
[0043]
In this case, the rasterizer 14 develops a multi-value bitmap image of Y, M, C, and K in the image memory. The image forming unit 19 that has received the raster image has a well-known binary value such as error diffusion or dither processing. The multi-value image signal is converted into a binary image signal by performing the digitization process, and then printed out. At this time, the optimum binarization method changes depending on the attribute of the image. In other words, graphics such as characters and figures are preferably binarized by reducing the dither matrix size and emphasizing resolution. For natural images such as photographs, it is better to increase the matrix size and emphasize tone reproducibility. preferable.
[0044]
In this way, in order to switch the binarization method according to the image, the rasterizer 13 does not perform conversion to CMYK but develops it into a bitmap image using RGB values, and sends the RGB sent on the image forming unit side. A character image area is detected from a bitmap image using a known image area separation method, and CMYK data is generated by switching a conversion method from RGB to CMYK in the detected character image area and other areas. It is also possible to output it.
[0045]
However, in this case, the image area separation method is not always capable of detecting 100% of the character area, and may be detected as a character area by mistake in the natural image area. There is a bug.
[0046]
On the other hand, according to the present embodiment, since the binarization method is switched using the attribute map information, the optimal binarization method can be easily and reliably applied to each image. For example, the 0th bit of the attribute map information corresponding to each pixel of the character image 116 and the graphic image 115 (Vector) is “0”, and the 0th bit of the attribute map information corresponding to each pixel of the natural image 114 (Bitmap) is “1”. For this reason, the natural image, the character image, and the graphic image can be easily separated for each pixel.
[0047]
The dither matrix shown in FIG. 8 is used for the pixels whose 0th bit is 1 in the attribute map, and the dither matrix shown in FIG. 9 is used for the pixels whose 0th bit is 0 in the attribute map. Here, the multi-value data used in this embodiment is 8 bits, 0 to 255 level, and when the value of the multi-value data of each pixel is larger than the threshold value of each cell of the dither matrix of FIGS. Then, if it is less than the threshold value of each cell, the dot is turned off.
[0048]
FIG. 8 is a diagram illustrating an example of a dither matrix having a size of 3 × 3. According to the dither matrix shown in FIG. 8, assuming that one pixel is 600 dpi, reproduction is possible at a resolution of 200 dpi, and the number of gradations is 10. Therefore, although the number of gradations is small, high-resolution image reproduction is possible. FIG. 9 is a diagram illustrating an example of a dither matrix having a size of 8 × 8. According to the dither matrix shown in FIG. 9, assuming that one pixel is 600 dpi, the number of gradations is 65 dpi, and the number of gradations is 65 gradations. Although the resolution is low, the number of gradations is large, and a natural image can be reproduced with higher quality than when the dither matrix shown in FIG. 8 is used.
[0049]
As described above, according to the present embodiment, since the dither matrix is switched for each pixel based on the attribute map information, it is possible to reproduce characters and graphics with high resolution while maintaining gradation in a natural image. It becomes possible to provide a high-quality image.
[0050]
[Second Embodiment]
In the first embodiment, the case where 1-bit information is provided as the attribute map has been described. However, the attribute information of each pixel of the attribute map is not limited to 1 bit. In the second embodiment, a case where 2-bit attribute information is adopted as an example of attribute information including a plurality of bits will be described.
[0051]
FIG. 12 is a diagram illustrating an example of a data format of attribute information according to the second embodiment. It has 0-bit and 1-bit 2-bit information, and the 0-bit is a Bitmap flag, which is the same as that described in the first embodiment. That is, if the Bitmap flag is “1”, it indicates a pixel generated from the Bitmap object, and if it is “0”, it indicates a pixel generated from the vector object, that is, a pixel in a character or graphic image.
[0052]
The first bit of the attribute map is a color flag. If it is 1, it indicates a color (color), and if it is 0, it indicates black and white (white, gray, black without color information).
[0053]
In this embodiment, the 0th bit and the 1st bit are independent, and the dither matrix is switched as in the first embodiment using the 0th bit information. Further, by referring to the 1-bit information, it is possible to perform further optimum image processing.
[0054]
For example, when color misregistration is significant as a characteristic of the image forming unit 19, when a character object having no color is output in a combination of four colors C, M, Y, and K, the color is misaligned, so that the color at the edge of a black character Appears and becomes unsightly. to solve this problem,
C '= C-min (C, M, Y)
M '= M-min (C, M, Y)
Y '= Y-min (C, M, Y)
K = min (C, M, Y)
In this way, a process of newly creating C ′, M ′, Y ′, and K and replacing the color with K (black) as much as possible, so-called UCR (under color removal) process is used. In this case, the color (C, M, Y) information is not so much applied to the monochrome character image, and the color shift becomes inconspicuous. On the other hand, however, when a lot of black is included in the natural image, there is a problem that depending on the characteristics of the image forming unit 19, the saturation is lowered and the color becomes dull and unsightly. Thus, it is difficult to achieve high image quality for both character images and natural images.
[0055]
On the other hand, in the second embodiment, it is possible to perform appropriate image processing on both the character image and the natural image. By using the 2-bit attribute map shown in FIG. 12, each pixel has one of the following attribute information.
[0056]

[0057]
In the case of “Monochrome in Vector”, the above-described UCR processing is performed to prevent color misregistration. In the case of “Color in Bitmap”, the UCR processing is stopped so as not to cover K as much as possible. High quality and high quality images can be realized. Note that such appropriate use of color processing is performed by switching the conversion processing from RGB data to YMCK data according to the attribute information read in step S22 in step S23 in the flowchart of FIG.
[0058]
The important point here is that the attribute map has information hierarchically, so that it can be used from an inexpensive printer with limited functions to a high-value-added printer with many functions. . For example, by increasing the number of bits in the attribute map from 1 to 2, both the first embodiment and the second embodiment can be implemented. Then, if 2 bits are used as in the second embodiment, that is, if the number of bits is increased, finer image processing can be switched, and a higher quality image can be provided.
[0059]
Therefore, an inexpensive printer with limited functions can perform processing using only the lower bits of the attribute information, and a printer with more functions can perform advanced processing using more bits of attribute information. is there. In this way, it is basically configured to have attribute information that is frequently used by the lower bits, and by having information hierarchically from the 0th bit, the system has the same attribute map structure. A more appropriate configuration can be constructed according to characteristics (such as cost and image quality).
[0060]
[Third Embodiment]
In the second embodiment, the case where each of the plurality of bits of the attribute information is independent from each other has been described. However, the plurality of bits of the attribute information may be associated with each other. In the third embodiment, a case will be described in which a plurality of bits of attribute information are in a master-slave relationship with each other.
[0061]
FIG. 13 is a diagram illustrating an example of a data format of attribute information according to the third embodiment. This attribute information has 0-bit, 1-bit, 2-bit 3-bit information. The 0th bit is a Bitmap flag, and indicates a pixel generated from a Bitmap object if 1 and a pixel generated from a vector object if 0, that is, a character or graphic image, as in the first and second embodiments. .
[0062]
The first bit is a color flag. As in the second embodiment, 1 indicates color (color), and 0 indicates black and white (white, gray, black without color information).
[0063]
The second bit is a character flag. If it is 0, it indicates a character other than 1 and 1 indicates a character object.
[0064]
When information up to the second bit of the attribute map is used, the following becomes possible. For example, in FIG. 16, when the color of TEXT 116 is defined as black with R = G = B = 0, the optimal CMYK signal for this is expressed as an 8-bit density signal, C = M = Y = 0, And K = 255. That is, it is preferable to reproduce black characters using only black toner among the four colors of toner of the printer.
[0065]
On the other hand, if the pixel value of the specific pixel of the natural image 114 is R = G = B = 0, it is converted into C = M = Y = 0 and K = 255 as in the case of the character data. Originally, since the portion having the highest density in a natural image should be expressed only with black toner, the absolute density is insufficient. Therefore, in this case, it is preferable that the absolute density is increased by converting into values such as C = M = Y = 100 and K = 255.
[0066]
Further, when the graphic image 115 is an intermediate value between a character and a natural image, that is, R = G = B = 0, it is assumed that C = M = Y = 50 and K = 255 are optimal. Also in this case, the image area separation process is performed on the multi-value bitmap image transferred from the image memory, and the above-described color process (color process for R = G = B = 0) is adaptively switched. A method is also conceivable, but the same problem as described above (the image area separation method does not always detect 100% of the character area, and may be detected as a character area in the natural image area by mistake. Therefore, it cannot be prevented.
[0067]
On the other hand, if the attribute map information of the third embodiment is used, the character image 116 is composed of pixels in which the 0 bit of the attribute map is 1 and the 2 bit is 1, and the graphic image 115 is the 0 bit of the attribute map. Is 1 and the 2nd bit is composed of 0 pixels, and the natural image 114 (Bitmap) is composed of the 0th bit of the attribute map and 0 pixels. For this reason, a natural image, a character image, and a graphic can be easily separated for each pixel. Therefore, as described above, when R = G = B = 0, the character image portion has C = M = Y = 0 and K = 255, and the graphic image portion has R = G = B = 0. If it is, C = M = Y = 50 and K = 255, and if the natural image portion is R = G = B = 0, it is easy to set C = M = Y = 100 and K = 255. And it becomes realizable correctly and can realize a better image quality. Note that the above black processing can be realized by switching the color processing in step S23 based on the attribute information read in step S22 of FIG.
[0068]
As described above, a plurality of bits can be combined to give finer attributes.
[0069]
The difference between the third embodiment and the second embodiment is as follows.
[0070]
The 0-bit information and the 1-bit information are independent of each other, and the 0-bit information and the 1-bit information can be used alone, whereas the 2-bit information is used in combination with the 0-bit information. become. This time, since 2 bits of 0 bit and 2 bits are used, it is possible to give four kinds of attributes by the square of 2. If the combination is for 3 bits, it is possible to have 8 attributes if the combination is for 4 bits.
[0071]
As shown below, when both the 0th bit and the 2nd bit are 1, the background (the state where there is no object information) is designated. Although the object information is three (natural image, character image, graphic), four types of information corresponding to 2 bits can be held, and thus it is possible to have completely different attributes. Although the attribute of character is inconsistent in Bitmap, the second bit is not information that can be used independently, but is handled as subordinate information having a different meaning depending on the 0-bit information.
[0072]

[0073]
In the third embodiment, an attribute map based on a combination of a plurality of bits has been described. Although the 0th bit is independent information, the 2nd bit is an attribute subordinate to the 0th bit, and two bits are used in combination, and a plurality of bits are combined.
[0074]
Note that an attribute based on a combination of a plurality of bits does not have an independent attribute and can be configured so that it does not make sense unless combined. For example, as shown in FIG. 14, with the configuration of the 0th bit and the 1st bit,

It is also possible to configure the attribute information as follows. In either case, it is possible to increase the processing speed by omitting the processing for the pixel that is the background attribute.
[0075]
Note that the present invention may be applied to a system constituted by a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.) or an apparatus constituted by a single device.
[0076]
Another object of the present invention is to supply a storage medium storing software program codes for implementing the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium. Needless to say, this can also be achieved by reading and executing the program code stored in the.
[0077]
In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.
[0078]
As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
[0079]
Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.
[0080]
Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.
[0081]
【The invention's effect】
As described above, according to the present invention, when image data is printed out, appropriate data processing according to the attribute of each image included in the image data is realized, and the quality of the output image is improved.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an image processing system according to an embodiment.
FIG. 2 is a diagram illustrating an example of a data format of attribute information according to the first embodiment.
FIG. 3 is a diagram illustrating an example of attribute map information associated with each pixel.
FIG. 4 is a diagram illustrating an example of an attribute map storage method when image data and attribute map information are stored in the same storage medium.
FIG. 5 is a diagram illustrating another example of an attribute map storage method when image data and attribute map information are stored in the same storage medium.
FIG. 6 is a diagram illustrating another example of an attribute map storage method when image data and attribute map information are stored in the same storage medium.
FIG. 7 is a diagram illustrating another example of an attribute map storage method when image data and attribute map information are stored in the same storage medium.
FIG. 8 is a diagram illustrating an example of a dither matrix having a size of 3 × 3.
FIG. 9 is a diagram illustrating an example of a dither matrix having a size of 8 × 8.
FIG. 10 is a flowchart illustrating drawing of an object and generation of an attribute map according to the present embodiment.
FIG. 11 is a flowchart illustrating a procedure for generating CMYK data by the image processing unit 17;
FIG. 12 is a diagram illustrating an example of a data format of attribute information according to the second embodiment.
FIG. 13 is a diagram illustrating an example of a data format of attribute information according to the third embodiment.
FIG. 14 is a diagram showing another example of a data format of attribute information according to the third embodiment.
FIG. 15 is a diagram showing a general schematic configuration of a system for outputting a document created by a host computer using a printer or the like.
FIG. 16 is a diagram illustrating three image forms of a natural image, a character image, and graphics.

Claims (25)

Generating means for generating a bitmap image based on the input object data;
Holding means for holding attribute information representing the attribute of the input object data in association with each pixel of the bitmap image generated by the generating means;
Conversion means for converting the bitmap image generated by the generation means into data that can be processed by the image output unit;
Switching means for switching processing contents in the conversion means based on the attribute information held in the holding means ,
The attribute information is composed of a plurality of bits, each of the plurality of attributes constituting the attribute information is assigned to each of the plurality of bits,
Wherein the plurality of the plurality of attributes assigned to each bit of the bit, the image processing according to claim Rukoto assigned to the lower bits of said plurality of bits more frequently with many attributes to be used in common by different printers capable apparatus. The image processing apparatus according to claim 1, wherein the holding unit holds an attribute map in which attribute information is arranged for each pixel in association with a two-dimensional coordinate position of the bitmap image. The image processing apparatus according to claim 1, wherein the holding unit embeds the attribute information in a part of bits of each pixel data of the bitmap image. The image processing apparatus according to claim 1, wherein the attribute information includes information indicating whether the corresponding object data is in the form of bitmap data or vector data. The converting means includes processing for converting the bitmap image generated by the generating means into binary data using a dither matrix,
The image processing apparatus according to claim 1, wherein the switching unit changes a dither matrix used in the conversion unit based on the attribute information. The generating means generates a bitmap image in RGB color space,
The conversion means includes a color conversion process for converting each pixel data of the bitmap image into pixel data represented in a YMCK color space,
The image processing apparatus according to claim 1, wherein the switching unit changes an algorithm of the color conversion processing based on attribute information held by the holding unit. The image processing apparatus according to claim 1, wherein the switching unit switches processing contents of the conversion unit according to an on / off state of each bit. The image processing apparatus according to claim 7, wherein each bit of the attribute information represents an independent attribute. The image processing apparatus according to claim 7, wherein the attribute information includes a bit group that represents a specific attribute by a plurality of bits. The image processing apparatus according to claim 1, wherein the object data is expressed in a page description language. A generation step of generating a bitmap image based on the input object data;
A holding step of holding attribute information representing an attribute of the input object data in a memory in association with each pixel of the bitmap image generated in the generation step;
A conversion step of converting the bitmap image generated in the generation step into data that can be processed by the image output unit;
A switching step of switching the processing content in the conversion step based on the attribute information held in the holding step ,
The attribute information is composed of a plurality of bits, each of the plurality of attributes constituting the attribute information is assigned to each of the plurality of bits,
Wherein the plurality of the plurality of attributes assigned to each bit of the bit, the image processing according to claim Rukoto assigned to the lower bits of said plurality of bits more frequently with many attributes to be used in common by different printers capable Method. The image processing method according to claim 11, wherein the holding step holds, in a memory, an attribute map in which attribute information is arranged for each pixel in association with a two-dimensional coordinate position of the bitmap image. The image processing method according to claim 11, wherein in the holding step, the attribute information is embedded in a part of bits of each pixel data of the bitmap image. The image processing method according to claim 11, wherein the attribute information includes information indicating whether the corresponding object data is in the form of bitmap data or vector data. The converting step includes a process of converting the bitmap image generated in the generating step into binary data using a dither matrix.
The image processing method according to claim 11, wherein the switching step changes a dither matrix used in the conversion step based on the attribute information. The generating step generates a bitmap image in an RGB color space,
The conversion step includes a color conversion process for converting each pixel data of the bitmap image into pixel data represented in a YMCK color space,
The image processing method according to claim 11, wherein the switching step changes an algorithm of the color conversion processing based on the attribute information held in the holding step. The image processing method according to claim 11, wherein the switching step switches processing contents of the conversion step in accordance with an on / off state of each bit. The image processing method according to claim 17, wherein each bit of the attribute information represents an independent attribute. The image processing method according to claim 17, wherein the attribute information includes a bit group representing a specific attribute by a plurality of bits. The image processing method according to claim 11, wherein the object data is expressed in a page description language. An image processing apparatus according to any one of claims 1 to 10,
A printer comprising an image output unit for forming a visible image on a recording medium using data obtained by the conversion means. An image processing system including a host device and an image output unit,
Generating means for generating a bitmap image based on the input object data;
Holding means for holding attribute information representing the attribute of the input object data in association with each pixel of the bitmap image generated by the generating means;
Conversion means for converting the bitmap image generated by the generation means into data that can be processed by the image output unit;
Switching means for switching processing contents in the conversion means based on the attribute information held in the holding means ,
The attribute information is composed of a plurality of bits, each of the plurality of attributes constituting the attribute information is assigned to each of the plurality of bits,
Wherein the plurality of the plurality of attributes assigned to each bit of the bit, the image processing according to claim Rukoto assigned to the lower bits of said plurality of bits more frequently with many attributes to be used in common by different printers capable system. The attribute, the image processing apparatus according to claim 1, characterized in that the corresponding object data contains data indicating whether the color attribute is monochrome attribute. The attribute, the image processing apparatus according to claim 1, characterized in that includes information corresponding object data representing whether the attribute other than or character a character attribute. A storage medium storing a control program for image processing, the control program being stored in a computer,
A generation process for generating a bitmap image based on the input object data,
A holding step of holding attribute information representing an attribute of the input object data in a memory in association with each pixel of the bitmap image generated in the generation step;
A conversion step of converting the bitmap image generated in the generation step into data that can be processed by an image output unit;
Based on the attribute information held in the holding step, to execute a switching step for switching the processing content in the conversion step ,
The attribute information is composed of a plurality of bits, each of the plurality of attributes constituting the attribute information is assigned to each of the plurality of bits,
Wherein the plurality of the plurality of attributes assigned to each bit of the bit, the more attributes frequently used in common by different printers capable allocated to low-order bits of said plurality of bit storage medium characterized Rukoto .

Images