JPS63271672A - Graphic output controller - Google Patents

Abstract

PURPOSE:To reduce the load on a host device by performing clipping processing by a drawing circuit with a clipping frame. CONSTITUTION:A command outputted by a host CPU is accepted by a command acceptance part 21 and analyzed to perform necessary processing. The command acceptance part 21 is realized by firmware. The drawing circuit 22 and a RAM as hardware perform coordinate transformation, clipping, painting, etc., at a high speed at a request from the command acceptance part 21. The RAM 23 is stored with a clipping frame control table 24 which controls information on a clipping frame defined by the host CPU, a clipping graphic information area 25 where the graphic information for defining the clipping frame is stored, and a bit map area 26 for clipping where the clipping graphic information is stored while expanded into a clipping bit map.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] “(Industrial Application Field) The present invention relates to a graphic output controller having a graphic clipping function.

(Prior Art) In recent graphic processing, it is required to clip a graphic formed by using a designated closed graphic as a clipping frame and display it on a screen, for example.

However, since general graphic display devices can only handle rectangles as clipping frames, it has been impossible to clip an arbitrary closed figure.

On the other hand, bitmap display devices often have a hardware circuit for processing raster operations at high speed, and by having the host CPU utilize the main hardware circuit, clipping using arbitrary shapes can be achieved. be able to.

FIG. 4 shows a schematic block configuration around the bit blit (bit block transfer) arithmetic circuit 11, which is such a hardware circuit. Using this circuit 11, for example, a plurality of parallel lines shown in FIG.
The procedure for clipping using the triangular clipping frame shown in b) to obtain the figure shown in FIG. 5(C) is as follows.

(2) The host CPU first creates the bitmap shown in FIG. 6 based on the clipping frame shown in FIG. 5(b). The bitmap shown in FIG. 6 is used as the mask bitmap 12 shown in FIG.

(2) Next, the host CPU draws parallel lines shown in FIG. 5(a) on the source bitmap 13 shown in FIG. 4.

∎ Based on the preparations in ① and ② above, the host CPU only uses the source bitmap 13 and the mask bitmap 12 whose AND for each pixel at the same position is 1111+ (displayed in monochrome for the sake of simplicity). ), the command to write to the destination 15 of the frame buffer 14 is
It is applied to the bit brit arithmetic circuit 11.

In the bitmap display device, clipping using a clipping frame of an arbitrary shape is possible through the above procedure.

However, in the above method, the host CPU must secure and release bitmap areas for sources and masks, and must also create bitmaps, especially bitmaps for masks.
There was a problem with the load increasing. This problem was more noticeable when the shape of the clipping frame was complex.

(Problems to be Solved by the Invention) As described above, conventionally, when attempting to realize clipping using a clipping frame of an arbitrary shape, there has been a problem that the load on the host device (host CPU) increases.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a graphic output controller that can perform clipping using a clipping frame of an arbitrary shape without increasing the load on the host device.

[Structure of the Invention] (Means for Solving Problems) This invention provides a clipping graphic information If area, a clipping bitmap area, a clipping frame identifier,
A clipping frame management table in which clipping frame information is registered, including a first pointer indicating the storage location of clipping graphic information regarding the clipping frame indicated by the identifier, and a second pointer indicating the expansion destination of bitmap information regarding the clipping frame indicated by the above identifier. A memory in which a command is placed, a command receiving means for receiving, interpreting and executing commands from a host device, and a drawing circuit activated by the command receiving means are provided. In response to the reception of the clipping frame definition command, the command reception means registers clipping frame information including the clipping frame identifier specified by this command in an empty entry of the clipping frame management table, and also registers the first clipping frame information registered in the same entry. The clipping graphic information specified by the clipping frame definition command is stored in the clipping graphic information area indicated by the pointer. Further, the command reception means activates a drawing circuit in response to reception of a clipping start command or a figure drawing command. When this drawing circuit is activated in response to reception of a clipping start command, the clipping figure information indicated by the first pointer registered in the entry in the clipping frame management table corresponding to the clipping frame identifier specified by this command The clipping figure information is extracted from the area, developed into bitmap information, this bitmap information is stored in the clipping bitmap area indicated by the second pointer registered in the same library, and the figure! J- When activated in response to reception of a drawing command, the command reception uses the means to execute a drawing command based on the bitmap information corresponding to the clipping frame identifier specified in the most recently received clipping start command. Determine whether each pixel of the figure specified by can be written to the frame buffer.

(Operation) According to the above configuration, when the host device defines a clipping frame of an arbitrary shape and then requests development into a bitmap corresponding to the clipping frame, from then on, all it has to do is specify the figure to be clipped. Since clipping using the defined clipping frame is performed in the drawing circuit, the load on the host device is reduced.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of a bitmap display device to which the present invention is applied. In the figure, 20 is a display controller, 30 is a frame buffer that stores display data in the form of bit images, and 40 is a display monitor that displays the display data stored in the frame buffer 30 on a screen. The display controller 20 is
A command receiving section 21 is provided to receive commands output from a host CPtJ (not shown), analyze them, and perform necessary processing. In this embodiment, the command reception unit 21 is realized by firmware. The display controller 20 further includes a drawing circuit 22 and a RAM 23, which are hardware mechanisms that perform coordinate conversion, clipping, filling, etc. at high speed in response to requests from the command receiving section 21. In RAM23, host C
A clipping frame management table 24 that manages information on the clipping frame defined by the PU, a clipping figure information area 25 that stores figure information that defines the clipping frame (clipping figure information), and a clipping bitmap (mask bit) that stores the clipping figure information. A clipping bitmap area 26 is placed in which the clipping bitmap area 26 is stored in an expanded form.

FIG. 2 mainly shows the entry structure of the clipping frame management table 24. As shown in the figure, the management table 24
has the following fields: clipping frame number, information flag, control flag, clipping frame origin, graphic information pointer, and bitmap information pointer.

Each of the above columns will be explained below.

(2) Clipping Frame Number This is a number (identifier) for identifying a registered clipping frame, and any number can be used as long as it is unique within the management table 24. This clipping frame number is specified by the host CPU when defining the clipping frame.

■Information flag This flag represents the format of clipping graphic information. As described later, there are two formats for clipping graphic information: a vector format and a bitmap format, and this flag indicates which format it is.

(2) Dollar Control Flag This flag indicates whether or not the corresponding clipping graphic information is developed in the clipping bitmap area 26 in the form of a clipping bitmap.

(2) Clipping frame origin display This is given in the coordinate system on the display screen of the monitor 40 and indicates the origin (0,0) of the coordinate system in which clipping information is written. Therefore, the clipping graphic information is written relative to the origin of the clipping frame, and by moving this point, the entire clipping frame can be moved.

■Graphic Information Pointer This is a pointer that specifies the storage location in the graphic information area 1425 of the corresponding clipping graphic information. There are two types of clipping graphic information formats:

1) Vector Format A figure surrounding a closed area is defined by a format described using normal figure definition commands, a series of commands that define straight lines, arcs, etc. All commands are written relative to the clipping frame origin.

2) Bitmap description format This is a format in which a bitmap serving as a clipping mask is described, and is expressed as a series of rectangular information. One piece of rectangle information is expressed by the coordinates of the pixel at the upper left corner of the rectangle relative to the origin of the clipping frame, its width, and height (all units are pixels).

(2) Pitmap information pointer This is a pointer that specifies the destination in the clipping bitmap area 26 of the corresponding clipping bitmap.

Of the various commands passed from the host CPU to the display controller 20 (command reception unit 21), the commands related to clipping processing are as follows.

■ Clipping frame definition command parameters are a clipping frame number, clipping frame origin, clipping figure information format, and clipping figure information.

■Clipping frame deletion command ・The parameter is the clipping frame number.

■The clipping frame origin change command parameters are the clipping frame number and the clipping frame origin.

(2) Clipping frame information change command parameters are a clipping frame number, clipping figure information format, and clipping figure information.

■Clipping start command The parameter is the clipping frame number.

■Clipping end command There are no particular parameters.

Next, the operation of one embodiment of the present invention will be explained with reference to the flowchart of FIG.

■Remaining clipping frame First, in order to define the clipping frame, the host CPU displays the clipping frame definition command to the controller 2.
Command acceptance of 0 is output to section 21. When the command reception unit 21 receives a command from the host CPU,
The command is analyzed (step 81). When the command from the host CPU is a clipping frame definition command as in this example, the command reception unit 21 registers the clipping frame information specified by the clipping frame definition command in an empty entry in the clipping frame management table 24 ( Step 82). In other words, command reception is done in part 2.
1 writes the clipping frame number specified by the above command in the clipping frame number column of an empty entry in the management table 24, sets the information flag to indicate the specified clipping figure information format, and writes the clipping frame origin column in the clipping frame origin column. Writes the specified clipping frame origin to . The command reception unit 21 also secures a clipping figure information storage area in the clipping figure information area 25, stores the clipping figure information specified by the above command in this secured area, and manages the storage location of the clipping figure information. It is written in the graphic information pointer field in the corresponding entry in the table 24 (step 83).

■When the clipping start host CPU outputs a figure using the clipping frame defined by the clipping frame definition command,
First output the clipping start command. When the command reception unit 21 receives a clipping start command from the host CPU, it searches the clipping frame management table 24 using the clipping frame number specified in the command as a search key, and registers the clipping frame number that matches this search key. The control flag of the entry currently entered is checked, and this search key is held as the current clipping frame number (step 84). Next, if the control flag checked in step S4 does not indicate that the bitmap has been expanded, the command reception unit 21 secures a clipping bitmap expansion area in the clipping bitmap 1Ii 126 and points the pointer indicating the secured area. The information is written to the bitmap information pointer in the corresponding entry of the clipping frame management table 24 (steps 85, 36). Then, the command reception unit 21 expands the clipping bitmap to the above-mentioned secured area.
A request is made to the drawing circuit 22 (step 87).

By the way, clipping bitmaps require a large area. Therefore, in this embodiment, the clipping bitmap area 26 is used as a first-in-first-out (FIFO) buffer, and the bitmap area 26 is
If the bitmap development area cannot be secured due to LL (full), the area where the oldest bitmap was developed is released and reserved as a new bitmap development area, thereby making efficient use of the bitmap area 26. .

In addition, when releasing an area where a bitmap has already been developed and securing a new bitmap area, control of the entry in the management table 24 in which clipping frame information defining the clipping bitmap before release is registered is performed. The flag is in the bitmap information unexpanded state.
! I can be replaced.

Now, when the drawing circuit 22 receives a request for bitmap expansion from the command receiving section 21, it refers to the entry in the clipping frame management table 24 in which the current clipping frame number is registered, and the graphic information in this entry is The corresponding clipping figure information is extracted from the clipping figure information area 25 specified in the pointer field. Then, the drawing circuit 22 determines the format of this retrieved graphic information based on the information flag in the reference entry, and based on the determination result, creates a clipping bitmap (here, pixels that are not clipped are LIT, pixels that are clipped are Expand it into a bitmap (such as O゛′),
It is stored in the clipping bitmap area 26 designated by the bitmap information pointer field in the reference entry. When the drawing circuit 22 completes the above operations, it notifies the command reception unit 21 of this fact. As a result, the command reception unit 21 reads the control flag checked in step S4.
Changes itself to bitmap expanded designated state (step S8)
), which has command output from the host CPU. If the control flag checked in step S4 already indicates that the bitmap has been expanded, the command reception section 21 does nothing and enters a state of waiting for command output from the host CPU.

(2) After outputting the clipping start command, the graphics drawing host CPU then outputs a series of commands (solid drawing commands) for drawing graphics to be clipped. When the command reception unit 21 receives a series of figure drawing commands from the host CPU, the command reception unit 21 sequentially sends the commands to the drawing circuit 22.
(step 89). The drawing circuit 22 accepts a command when drawing a figure on the frame buffer 30 in accordance with a figure drawing command passed from the unit 21, and receives a command from a clipping frame in which the current clipping frame number held by the unit 21 is registered. Refer to the entry in the frame management table 24 and use the clipping bitmap developed in the clipping bitmap area 26 specified in the bitmap information pointer field.
Only the pixels corresponding to the 11-filled positions are written to the frame buffer 30.

As a result, the graphic specified by the host CPU is clipped.

(2) Clipping End After the host CP outputs a series of mouth shape drawing commands, it finally outputs a clipping end command. When the command reception unit 21 receives this clipping end command, it sets the current clipping frame number held by itself to an undefined state (step 510).

(2) Clipping frame deletion The host CPU outputs a clipping frame deletion command when the clipping frame defined by the clipping frame definition command becomes unnecessary. When the command reception unit 21 receives this clipping frame deletion command, it searches the clipping frame management table 24 using the clipping frame number specified by the command as a search key. Then, the command reception unit 21 releases the graphic information storage area in the clipping graphic information area 25 specified in the graphic information pointer field in the purpose entry of the management table 24, and furthermore, the corresponding clipping graphic information has been developed into a bitmap. If so, the corresponding expansion area in the clipping bitmap area 26 is released, and the target entry is made a free entry (step 511).

■Changing the Clipping Frame If the clipping frame origin changes during the process, the host CPU outputs a clipping frame origin change command. When the command reception unit 21 receives this command, the host CPU outputs a clipping frame origin change command. The content of the clipping frame origin column of the entry in the clipping frame management table 24 in which the frame number is registered is rewritten to the value specified by the above command (step 512).

Similarly, if the clipping frame shape changes during the process, the host CPU outputs a clipping frame information change command. When the command reception unit 21 receives this command, it transmits the clipping figure information in the clipping figure information area 25 indicated by the figure information pointer field in the entry in the clipping frame management table 24 in which the clipping frame number specified by the command is registered. is replaced with the graphic information specified by the above command (step 513). if,
If the format of the graphic information is also changed, the command reception unit 21 also rewrites the information flag in the above entry (steps 814 and 815>.Furthermore, the command reception unit 21 changes the control flag in the entry to If it indicates that the bitmap has been expanded, this control flag is rewritten to indicate that the bitmap has not been expanded, and the corresponding bitmap expansion area in the clipping bitmap area 26 is released (step 816.$17).

The clipping frame mentioned in the above explanation is
Of course, it can be used as a window. When using a clipping frame as a window, it is possible to support windows of arbitrary shapes. In addition, in the case of support for general rectangular windows, by using the entire complex-shaped polygonal area resulting from overlapping windows as a clipping frame, the window control performed by the host CPU can be performed on the display controller 20 side. becomes possible.

Furthermore, the present invention is applicable not only to a display controller (graphic output controller for display control) of a bitmap memory display device, but also to a graphic output controller of a high-performance printer device (such as a laser beam printer) having a graphic processing function. can.

[Effects of the Invention] As detailed above, according to the present invention, clipping using a clipping frame of an arbitrary shape can be realized without causing an increase in the load on the host device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a bitmap display device to which the present invention is applied, FIG. 2 is a diagram mainly showing the entry structure of the clipping frame management table 24 shown in FIG. 1, and FIG. The command reception shown in FIG. 1 is a flowchart showing the operation procedure of the section 21, FIG. 4 is a diagram explaining general ripping processing, and FIG. 5 shows an example of a clipping umbrella figure, a clipping frame, and a figure after clipping. 6 are diagrams showing examples of clipping bitmaps (mask bitmaps). 20... Display controller, 21... Command reception unit, 22... Drawing circuit, 23... RAM (memory), 24... Clipping frame management table, 25...
... Clipping graphic information area, 26... Bitmap area for clipping, 30... Frame buffer. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 (Saki no 1) Figure 3 (Be/12) Figure 3 (4/+3)

Claims (1)

[Claims] A clipping figure information area in which clipping figure information defining a clipping frame is stored, a clipping bitmap area in which the clipping figure information is developed into bitmap information, a clipping frame identifier, and a clipping frame identifier indicated by the identifier. A clipping frame management table is placed in which clipping frame information is registered, including a first pointer indicating a storage location of clipping graphic information related to the clipping frame, and a second pointer indicating a destination of developing bitmap information related to the clipping frame indicated by the above-mentioned identifier. a memory, a command receiving means for receiving, interpreting and executing commands from a host device, and when this command receiving means is activated by receiving a clipping start command, the command receiving means corresponds to the clipping frame identifier specified in the above start command. The first item registered in the entry in the clipping frame management table
extracting clipping figure information from the clipping figure information area indicated by the pointer, developing it into bitmap information, and storing this bitmap information in the clipping bitmap area indicated by the second pointer registered in the same entry; When activated by the reception of a figure drawing command by the command reception means, the bitmap information corresponding to the clipping frame identifier specified in the clipping start command most recently received by the command reception means is used. and a drawing circuit that determines whether each pixel of the figure specified by the figure drawing command can be written to the frame buffer, and the command receiving means receives the clipping frame identifier and the clipping frame from the host device. When a clipping frame definition command that includes graphic information is received, the clipping frame information that includes the above clipping frame identifier specified by this command is registered in the free entry of the above clipping frame management table, and the clipping frame information that is registered in the same entry is The graphic output controller is configured to write clipping graphic information designated by the clipping frame definition command into the clipping graphic information area indicated by the first pointer.