JP5028372B2 - Image processing apparatus, image processing method, and image processing program - Google Patents

Description

  When converting a page description language capable of expressing a drawing object having a transparency attribute and a canvas having a transparency attribute, which is a foundation for drawing the drawing object, into the intermediate language, the conversion process and the synthesis process of the transparency are performed. The present invention relates to an image processing apparatus, an image processing method, and an image processing program that can be performed.

  In a page description language written in an XML extension format such as XPS, there are cases where a canvas that is the basis for drawing a drawing object (path, font, image, etc.) is described in a nested structure with multiple layers, When converting a page description language having a nested canvas structure into an intermediate language for printing or display, alpha blending operations (transparency and color value composition) of the canvases and the drawing objects contained therein There has been no method for efficiently performing the alpha blend calculation processing when performing the calculation for

  As a conventional technology, when the opacity (alpha value) is included in the color specification of the page description language document and those colors overlap each other, alpha blend calculation processing is required. Rendering results vary depending on whether the device color gamut is compressed before processing, or the device color gamut is compressed before alpha blend processing is performed. There has been a method of selecting an appropriate method (see Patent Document 1).

However, even in this method, the alpha blend operation is only processed sequentially, and a method corresponding to the canvas having the above-described nested structure is not disclosed.
JP 2006-345197 A XML Paper Specification, XPS Specification and Reference Guide Version 1.0

  The problem to be solved is that, in an image processing apparatus, an image processing method, and an image processing program for performing image processing for converting a page description language into an intermediate language, a canvas having a transparency attribute exists in the page description language in a nested structure In this case, there is no intermediate language data structure suitable for executing the alpha blend operation processing, and there is no efficient method for performing the alpha blend operation processing.

The image processing apparatus according to the first aspect of the present invention is an image processing apparatus that performs image processing for converting a page description language into an intermediate language, and a canvas having a transparency attribute exists in the page description language in a nested structure. The intermediate language conversion unit that converts the intermediate structure to the intermediate language having the nested structure and the recursion corresponding to the nested structure of the canvas when synthesizing the transparency attribute of the nested canvas described in the intermediate language. The main feature is that it has an alpha blend operation unit that performs transparency attribute composition processing by an algorithm . Here, the canvas is an object that serves as a basis for drawing objects (paths, fonts, and images) described in the page description language in the XML extension format. The transparency value indicating transparency and the transparency indicating the transparency distribution are also included. It has a transparency attribute such as a mask.

The image processing apparatus according to claim 2 is the image processing apparatus according to claim 1, wherein the recursive algorithm draws in a buffer reserved for temporarily holding a color at the start of the canvas. The main feature is that processing is performed and the buffer is used as an image at the end of the canvas, and drawing is performed while performing alpha blending on the next lower canvas . Here, synthesizing color values based on the color value, transparency, canvas color value, and transparency of the drawing object is called alpha blending.

An image processing apparatus according to a third aspect of the present invention is the image processing apparatus according to the first or second aspect, wherein the page description language is described in an extended markup language (XML) extended format. To do.

The image processing method of the present invention according to claim 4 is an image processing method for converting a page description language into an intermediate language, and when a canvas having a transparency attribute is present in a nested structure in the page description language, When the transparency attribute of the canvas of the nested structure described in the intermediate language is synthesized by converting to the intermediate language having the nested structure, the transparency attribute is synthesized by a recursive algorithm corresponding to the nested structure of the canvas The most important feature is processing.

The image processing program of the present invention according to claim 5 is an image processing program for causing a computer to realize a function of converting a page description language into an intermediate language, wherein a canvas having a transparency attribute is nested in the page description language. When the intermediate language conversion function for converting to an intermediate language having the nested structure and the transparency attribute of the nested canvas described in the intermediate language are synthesized, the nested structure of the canvas is included in the canvas. The most important feature is that the computer realizes an alpha blending calculation processing function for performing the synthesis processing of the transparency attribute by a recursive algorithm according to the above.

With the image processing apparatus according to the first aspect of the present invention, even a page description language of data having a nested canvas can be described by being converted into an intermediate language for printing or display. As a result, also in the alpha blend calculation processing, the composition of the color value and the transparency described in the original page description language can be faithfully reproduced. In addition, it is possible to faithfully reproduce the composition of the color value and the transparency described in the original page description language by using a simple algorithm for the alpha blend operation processing of the intermediate language data described in the nested structure.

  According to the image processing apparatus of the present invention, it is possible to faithfully reproduce the composition of the color value and the transparency described in the original page description language even if the page description language is in the XML extended format.

  According to the image processing method of the present invention described in claim 4, even a page description language of data having a canvas with a nested structure can be described by being converted into an intermediate language for printing or display. As a result, also in the alpha blend calculation processing, the composition of the color value and the transparency described in the original page description language can be faithfully reproduced. Furthermore, it is possible to faithfully reproduce the composition of the color value and the transparency described in the original page description language by a simple algorithm for the alpha blend operation processing of the intermediate language data described in the nested structure.

  According to the image processing program of the present invention described in claim 5, even a page description language of data having a canvas with a nested structure can be described by being converted into an intermediate language for printing or display. As a result, also in the alpha blend calculation processing, the composition of the color value and the transparency described in the original page description language can be faithfully reproduced. Furthermore, it is possible to faithfully reproduce the composition of the color value and the transparency described in the original page description language by a simple algorithm for the alpha blend operation processing of the intermediate language data described in the nested structure.

  An image processing apparatus, an image processing method, and an image processing program for performing image processing for converting a page description language into an intermediate language. When a canvas having a transparency attribute is present in a nested structure in the page description language, alpha blend operation processing A method of converting a point where there was no intermediate language data structure suitable for executing the method and a point where there was no method of efficiently performing an alpha blend operation process into an intermediate language that retains the nested structure; The intermediate language having the nested structure was solved by a method of performing an alpha blend operation by a recursive algorithm.

  An image processing apparatus according to an embodiment of the present invention will be described below.

[Synthesis of transparency attributes; alpha blending]
Alpha blending is a semi-transparent composition of two images each having a color value using a certain coefficient. This coefficient is called an alpha value and takes a value of 0.0 to 1.0. 0.0 indicates completely transparent, 1.0 indicates completely opaque overlay. In the PDF (Portable Document Format) and XPS (XML Paper Specification) document formats, alpha values can be set for objects such as path figures, fonts, and images. Synthesis of transparency and color values).

  The following explains how alpha blend transparency synthesis processing is performed using XPS document format data as an example.

Figure 1 shows the path data with transparency attribute expressed in XPS, and the steps for strictly performing alpha blending described in 11.4 Opacity Computations of XPS specification 1.0 (see Non-Patent Document 1) are as follows: Show.
(1): The alpha value on the source side is obtained. Multiply the alpha value of the source by the value of the Opacity attribute and the value of OpacityMask (transparency mask).

As1 = As * Oe * Om
As: Source element alpha value (see Figure 1)
Oe: Opacity value of the source element (see Fig. 1)
Om: OpacityMask (transparency mask) value of the source element at the pixel position to draw (see Figure 1)
(2): The alpha value (As1) obtained in (1) is applied to the source color value. This process is called Pre-multiply source alpha. Cs in the following expression is a value for each plane in the current color space such as RGB, Gray, or CMYK.

Cs_tmp = Cs * As1
Cs: Source color value (see Figure 1)
Cs_tmp: Temporary value of source side color value (3): Multiply destination side alpha by destination color value. This process is called Pre-multiply destination alpha. The destination pixel color value Cd in the following expression is a value for each plane in the current color space such as RGB, Gray, and CMYK, as in the source side.

Cd_tmp = Cd * Ad
Ad: Alpha value of the destination
Cd: Destination drawing pixel position color value
Cd_tmp: Temporary destination color value (4): Blend processing is performed.

A_tmp = (1-As1) * Ad + As1
C_tmp = (1-As1) * Cd_tmp + Cs_tmp
A_tmp: Temporary for checking (5)
C_tmp: Temporary for checking in (5) (5): A value to be written to the destination result is obtained. This process is called Reverse pre-multiplication.

If A_tmp = 0
{
Anew = Cnew = 0
}
Else
{
Anew = A_tmp
Cnew = min (C_tmp / A_tmp, 1)
}
The parameters appearing in (1) and (2) appear in the XPS document of FIG. 1 (see Non-Patent Document 1 for more details).

[Case of drawing on page]
In the blend processing step (3), the background is opaque in the drawing process on the page, that is, Ad = 1.0. In this case, as described below, the alpha blend process can be performed using only the source color value and alpha value and the destination color value already written on the page (see FIG. 2A).

As1 = As * Oe * Om
Anew = 1.0 (Opaque and unchanged)
Cnew = (1-As1) Cd + As1 * Cs (known as a simple alpha blend formula)
[If the canvas has no transparency attribute]
In the blend processing step (3), in the drawing process on the canvas, in the initial state, the background is completely transparent, Ad = 0.0 and no color Cd = 0.0 (black if RGB). This is the image of a glass plate.

As1 = As * Oe * Om
Anew = As1 (accumulated alpha value)
Cnew = Cs (the source color value remains the same)
If nothing is drawn on the canvas and the blending step is followed, as shown above, if the object on the canvas contains transparency, the color value and alpha value are accumulated on the canvas as they are. Will be. This indicates that the accumulated value affects the source alpha value when the canvas is drawn on a layer below the page or the like.

  However, when transparency is not set on the canvas itself, the result of drawing the completed canvas on the page is the same as when the object is directly written on the page (see FIG. 2B).

  In this case, it is not necessary to perform drawing in a buffer different from the page as shown in FIG. 2B, and the same processing as when the canvas is not defined may be performed.

[If the canvas has a transparency attribute]
As described above, the color value and the alpha value accumulate in the area where the object is drawn, but the other areas remain completely transparent at 0.0.

  Regarding the rendering method when transparency is set on the canvas itself, in the implementation method presented in the XPS specification, when the object drawing on the canvas is finished and written to the lower layer, the Opacity attribute of the canvas element And apply (combine) the values of OpacityMask to the accumulated alpha value. This means that in the blending step (1), Oe and Om of the canvas itself are multiplied by the accumulated alpha value.

  In addition, even if Opacity and OpacityMask are applied, the area where no object is drawn in the canvas remains in a state where nothing is drawn with an alpha value of 0.0. For this reason, the effect of the transparency processing is exerted only on the drawn object portion (see FIG. 3C).

  Conceptually, the steps described above are performed, but if the same processing is performed on the same canvas, if the objects overlap, the strict blending process of FIG. 2A taking into account the alpha value of the destination (FIG. 3D).

[Constitution]
FIG. 1 is a functional block diagram of an image processing apparatus according to an embodiment of the present invention.

  The image processing apparatus includes a communication interface 1.1, a data reception unit 1.2, a data analysis unit 1.3, a drawing data processing unit 1.4 (intermediate language conversion unit), and a drawing unit 1.5 (alpha blend calculation unit). , An output unit 1.6, a system control unit 1.7, an error control unit 1.8, and a memory management unit 1.9. Each functional unit will be described below.

  The communication interface 1.1 is a functional unit that performs communication with a host computer or the like.

  The data receiving unit 1.2 is a functional unit that receives data (print data written in a page description language) via the communication interface 1.1.

  The data analysis unit 1.3 is a functional unit that analyzes print data described in the page description language that has been sent.

  The drawing data processing unit 1.4 (intermediate language conversion unit) converts the page description language into an intermediate language (here, specifically, a display list) in accordance with an instruction from the data analysis unit 1.4.

  In a page description language described in an XML extended format such as XPS, there are elements such as paths, glyphs (fonts), and images that are drawing objects, and a canvas that serves as a basis for displaying these drawing objects. Each of these elements and canvases has a transparency attribute. Also, the canvas has a nested structure (nested structure), and the canvas and elements contained therein can be handled as one group.

  The drawing data processing unit 1.4 (intermediate language conversion unit) is configured to maintain the nested structure when converting the canvas data having the nested structure into the intermediate language. FIG. 5 shows the structure when one canvas object is converted into a display list.

  The canvas object is followed by a “Start” mark that indicates its start, a display list of drawing objects or canvas objects that exist on the canvas, an “End” mark that indicates the end of the canvas, and then the canvas transparency information. End with the “Write” command, which indicates the drawing to the lower layer.

  When the canvas has a nested structure, a pointer to the canvas object to be nested is inserted between the “Start” mark and the “End” mark.

  The drawing unit 1.5 (alpha blend operation unit) is a functional unit that creates bitmap data in the VRAM from the display list (intermediate language) created by the drawing data processing unit 1.4 (intermediate language conversion unit). Alpha blending calculation processing is performed in the drawing unit 1.5.

  The output unit 1.6 is a functional unit that outputs bitmap data obtained by performing image processing in each functional unit described above. The output may be printing on a recording medium such as paper or a method of performing display output on a display device.

  The system control unit 1.7 is a functional unit that manages common information of the system of the image processing apparatus and controls the system.

  The error control unit 1.8 is a functional unit that controls processing when an error occurs in the image processing apparatus.

  The memory management unit 1.9 is a functional unit that manages the memory of the system of the image processing apparatus.

[Alpha blending algorithm]
The alpha blend operation of the display list (intermediate language) having the nested structure shown in FIG. 5 is efficiently calculated by the recursive algorithm shown below.

  Considering the calculation composite for a single canvas, the calculation is as follows:

*** _ n represents the number of objects included in the canvas and represents the value of the calculation process.
[Algorithm description by pseudo code]
C = Composite (C_0, O_0)
Input C_0: Current color of the canvas drawing destination
O_0: Entire object included in canvas Output C: Color value of canvas {
S_0 = C_0 (Formula 1)
Repeat the following process for all objects (i from 1 to n)
{
If Obj_i is a canvas, recursive call {
C_i = Composite (SC_ (i-1), Obj_i) (Formula 2)
} Otherwise {
C_i = Obj_i_Color (Formula 3)
}
S_i = (1-Obj_i_Alpha) * SC_ (i-1) + Obj_i_Alpha * C_i (Formula 4)
}
C = S_i
} [End algorithm]
In other words, when the canvas is started, an area where the colors drawn so far are copied (Formula 1), and when the canvas is finished, the alpha value of the canvas itself is used for blending with the ground (Formula 4). . It is only necessary that the initial value S_0 is white at the start of the page.

[Specific example of processing contents]
Specific examples of processing contents of the recursive algorithm described above will be described below with reference to FIGS.

  The algorithm secures a buffer that temporarily holds colors at the start of the canvas, and performs drawing processing in the buffer. This is a method of drawing the buffer as an image at the end of the canvas while blending the next lower layer. If there is further nesting during drawing on the canvas, a recursive call is made, a buffer for holding the color is secured accordingly, and the canvas is processed as an upper level canvas.

  As an example of performing this process, consider a case where semi-transparent canvases are nested (nested), and semi-transparent objects overlap on the canvas.

  In FIG. 6E, a rectangular Object1 that is a drawing object exists on a Canvas1 having Opacity = 0.5 in the first stage expressed in XPS, and a second-stage Canvas2 having Opacity = 0.5 is nested. The triangle Object2 and Object3 exist on the second level of Canvas2.

  Fig. 6 (F) shows the drawing when all the XPS objects are assumed to have no transparency (Opacity), and Fig. 6 (G) shows the alpha blending calculation of transparency (Opacity) as described in XPS. The drawing is shown. However, since color notation is not possible, the drawing is converted to gray scale.

  FIG. 7 shows a processing procedure by the drawing unit 1.5 (alpha blend operation unit) for this data, and will be described in comparison with the formula of the recursive algorithm described above.

[Securing the page buffer]; FIG.
Allocate a page buffer that is the last page to be drawn first.

[Start Canvas1]; FIG. 7 (I)
Copy the result drawn in the page buffer so far to Canvas1 (Formula 1). Furthermore, Object1 on Canvas1 is drawn. (Formulas 3-4). The transparency information of Canvas1 is held in some form (for example, a local variable of a recursive call routine).

[Start Canvas2]; Fig. 7 (J)
Copy the result drawn on Canvas1 to Canvas2. (Recursive call with expression 2 and expression 1).

  Next, the objects (Object2, Object3) on Canvas2 are drawn. At this time, alpha blend calculation processing is performed on Canvas2 (Equations 3-4).

  Similarly, the transparency information of Canvas2 is held in some form (for example, a local variable of a recursive call routine).

[End of Canvas2]; Fig. 7 (K)
With Canvas2 itself transparency information (element Opacity value, OpacityMask value), Canvas2 is rendered as an image in Canvas1 (Step 4).

  Free the Canvas2 buffer.

[End of Canvas1]; Fig. 7 (L)
Draw Canvas1 as an image on the page using the transparency attribute information of the Canvas1 itself (Opacity value and OpacityMask value of the element) (Formula 4).

  Free the Canvas1 buffer.

  With the series of operations described above, alpha blending processing can be performed by a recursive algorithm.

[Effect of Example]
The image processing apparatus according to the embodiment of the present invention enables the following.

  When converting a page description language to an intermediate language for efficient synthesis (alpha blend operation) of drawing objects with a nested structure described in a page description language such as XPS and other XML extension formats, canvas transparency attributes Conversion was performed while maintaining the nested structure. Furthermore, the alpha blend operation of the intermediate language data having the nested structure is realized by a recursive algorithm.

  The above method makes it possible to efficiently perform alpha blending operations across nested structures.

  Using an intermediate language having the above structure, alpha blending calculation processing is performed, and then conversion to bitmap data is performed to enable printing processing on a printer.

[Others]
In the embodiment, the color values are based on the three primary colors of RGB. However, the color values may be CMYK color values, and an alpha blend operation is possible in the same manner.

This is a notation example of alpha value, color value, transparency and transparency mask by XPS. It is a conceptual diagram of the alpha blend (no transparency setting) at the time of the drawing on a canvas. It is a conceptual diagram of the alpha blend (with transparency setting) at the time of the drawing on a canvas. 1 is a functional block diagram of an image processing apparatus according to an embodiment of the present invention. It is an example of the data structure of the display list of the Example of this invention. A notation example (E) of a nested canvas in XPS and its corresponding drawing (with transparency setting (F) and without (G)). It is a figure ((H) to (L)) which shows a processing procedure of drawing of XPS data given in Drawing 6 (E).

Explanation of symbols

1.1 Communication interface 1.2 Data receiver 1.3 Data analyzer 1.4 Drawing data processor (intermediate language converter)
1.5 Drawing part (alpha blend operation part)
1.6 Output unit 1.7 System control unit 1.8 Error control unit 1.9 Memory management unit

Claims (5)

An image processing apparatus for performing image processing for converting a page description language into an intermediate language,
An intermediate language conversion unit for converting into an intermediate language having the nested structure when a canvas having a transparency attribute is present in the nested structure in the page description language ;
An alpha blend operation unit for performing transparency attribute synthesis processing by a recursive algorithm according to the canvas nesting structure when synthesizing the transparency attribute of the nested canvas described in the intermediate language. An image processing apparatus. The image processing apparatus according to claim 1,
The recursive algorithm performs drawing processing in a buffer reserved to temporarily hold colors at the start of the nested canvas, and at the end of the nested canvas, the buffer is used as an image one step below. Draw with alpha blending on the canvas,
An image processing apparatus. The image processing apparatus according to claim 1 or 2,
The image processing apparatus, wherein the page description language is described in an XML (Extended Markup Language) extended format. An image processing method for converting a page description language into an intermediate language,
When a canvas having a transparency attribute is present in a nested structure in the page description language, it is converted into an intermediate language that retains the nested structure,
An image processing method characterized in that when the transparency attribute of a canvas with a nested structure described in the intermediate language is synthesized, the transparency attribute is synthesized by a recursive algorithm according to the nested structure of the canvas. . An image processing program for causing a computer to realize a function of converting a page description language into an intermediate language,
An intermediate language conversion function for converting to an intermediate language having the nested structure when a canvas having a transparency attribute is present in the nested structure in the page description language;
An alpha blending operation processing function for performing the transparency attribute synthesis processing by a recursive algorithm according to the canvas nested structure when synthesizing the transparency attribute of the nested canvas described in the intermediate language; An image processing program to be realized in