JPH03208680A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To obtain a clear output image of high quality by determining a dot pattern at a lower gradation than the gradation of an input image data, and storing the dot pattern separately when the resolving power is low and when the resolving power is high. CONSTITUTION:It is detected whether or not the pixel is completely inside the character boundaries 31, 31'. If the pixel is completely accommodated within the character boundaries 31, 31' as a pixel 32, the image data of the subject pixel is plotted into an image memory 15. On the other hand, if the subject pixel is outside the character boundaries, it is checked whether or not the pixel is completely outside the character boundaries, and if the pixel is outside the boundaries as a pixel 33, the pixel 33 is subjected to clipping and not plotted. In the case where the pixel is found astride the character boundary 31' as an image pixel 34, the image pixel 34 stretches over the inside and outside the character outline. Therefore, the image data in the area of the image pixel 34 is plotted (stored) not in the video image memory 5, but in a character image memory 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus, for example, an image forming apparatus that synthesizes and outputs images from a plurality of types of frame buffers having different resolutions.

[Prior Art] Conventionally, in this type of device, when the amount of memory for storing image information is limited and the resolution and gradation are limited, there is a trade-off relationship between resolution and gradation. . For example, the memory capacity for storing image data of 600 dpi with no gradation (on and off), the memory capacity of image data of 300 dpi with 16 gradations, and the memory capacity of 150 dpi with 256 gradations are the same.

Now, in order to obtain high-quality output results with a small amount of memory, it is necessary to store character images (images made up of characters) and image images (images of photographs, paintings, etc.) in separate image memories with different resolutions. be. In this case, as an example, the character image memory has no gradations at 600 dpi, and the image image memory has 64 gradations at 150 dpi. The reason for this is that character images generally require higher resolution than images, and images that have a certain degree of gradation appear higher quality to the naked eye. All character images are drawn in the character image memory, image images are drawn in the image image memory, and the respective images are output in a superimposed manner. In this way, both the character image portion and the image image portion have high quality.

[Problem to be Solved by the Invention] However, in the above conventional example, there is no problem if the character area and the image area are separated.
If you try to draw an image by overlaying text on top of the image, cutting out the image into the shape of a letter, or filling in the text with an image (critting the image with the outline of the letter), the difference between images may occur. The difference in resolution is a problem. That is, there are disadvantages in that gaps may occur at the outline of the character or at the boundary between the character and the image, resulting in an unnatural-looking image.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and an object thereof is to provide an image forming apparatus that can obtain clear and high-quality output images.

[Means for Solving the Problems] In order to solve the above-mentioned problems and achieve the objectives, an image forming apparatus according to the present invention inputs image data having gradation and resolution attributes. an input means; a determining means for determining a dot pattern at a gradation lower than the gradation based on the gradation of the input image data; It is characterized by comprising a storage means for storing dot patterns divided into low resolution or high resolution, and a forming means for forming an image based on the stored dot patterns of each resolution.

[Operation] According to this configuration, the input means inputs image data having gradation and resolution attributes, and the determining means determines a dot pattern at a lower gradation based on the gradation of the input image data. The storage means stores the dot patterns determined based on the resolution attribute of the input image data divided into low resolution or high resolution, and the formation means forms an image based on the stored dot patterns of each resolution. do.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of an image forming apparatus of the present invention. In the figure, 1 indicates a printer that is an embodiment of the present invention, and 20 indicates a host computer for transmitting data to the printer 1. 3 is a CPU that controls the overall operation of the printer 1; 4 is a character image memory for creating a character image with a low resolution attribute or storing data of the character image; 5 is a character image memory for creating an image with a high resolution attribute. Each of the figures shows an image memory for storing the data of the image. Incidentally, in the character image memory 4 and the image image memory 5, bits to which no data is written are set to ゛゜O゛. 6
7 is a program ROM in which programs and error programs according to the flowcharts shown in FIGS. 4 and 7 for controlling the printer 1 are stored, and 7 is an R used as a work area for various programs and a temporary save area during error processing.
AM is shown respectively. 8 is a video signal line for transmitting a video signal of a character image to the output section 10; 9 is a video signal line for transmitting a video signal of an image image to the output section 9; 10 is a line for transmitting each video signal onto a sheet of paper; An output section for forming a visual image is shown in each case. Furthermore, the output section 10
The configuration is such that each video signal (character image and image image) sent from video signals 8 and 9 is outputted by ORL.

The character image memory 4 is a bitmap memory having a capacity for one page, and here, one pixel of black and white is represented by one bit of ON/OFF.

On the other hand, the image memo I) 5 is a byte map memory having a capacity of one page, and here, the gradation of one pixel is represented by one byte. The gradations are represented by 256 gradations from O to 255, and the output unit 10 can express each pixel of the image on the paper at each gradation.

Next, FIG. 2 is a diagram for explaining the difference in size between image pixels and character pixels according to this embodiment, and FIG. 3 is a diagram showing an example of output according to this embodiment.

In FIG. 2, the image pixel numbered 21 is 1 5
The character pixel indicated by 22 is output at 600 d p i (dots per inch).
Output as pi. That is, the image pixel 21 has an area equivalent to 16 character pixels 22 (4×4=16).

As explained in Fig. 2, the size of character pixels and the size of image pixels are different, so as shown in Fig. 3, the character boundary line (31 in Fig. 3) indicating the outline of the character is A situation occurs in which the image traverses inside the pixel. In this case, the output image from the output unit 10 has a matrix (plane) occupied by one image pixel in which an image portion and a character portion are mixed.

Here, the operation of this embodiment will be explained.

FIG. 4 is a flowchart illustrating the operation of cribbing an image with the outline of a character according to this embodiment.

When drawing an image, one pixel (150x150d
The process in FIG. 4 is repeated for each pi). This is the third
To explain using the example shown in the figure, first, in step S1, it is determined whether the pixel is completely inside the character boundary 31, 31'. If the target pixel does not straddle the character boundary 31 or 31° like the pixel indicated by 32 in FIG. The image data of the pixels are drawn in the image image memory 5. On the other hand, if it is not inside, it is determined in step S3 whether it is completely outside the character boundary 31, 31'. As a result, 3 in Figure 3
If the pixel 33 is outside like the pixel indicated by 3, that pixel 33 becomes a clipping target and is not drawn because it is outside the boundary, so that pixel 33 can be said to have been clipped. Processing for that pixel ends without drawing. If it is not outside in step S3, that is, the third
When it is determined that the pixel straddles the character boundary 31°, such as the image pixel 1 1 indicated by 34 in the figure, the image pixel 34 straddles both the inside and outside of the character outline (character boundary). In step S4,
As will be described later, processing is performed when an image pixel straddles a character boundary. At this time, the image data in the area of the image pixel 34 is drawn (stored) in the character image memory 4 instead of the image image memory 5.

The details of step S4 will be explained below.

FIGS. 5 and 6A to 6F are diagrams illustrating a method of expressing using black dots according to the gradation of image pixels according to this embodiment.

As mentioned above, there are 16 pixels in the area of one image pixel.
Contains character pixels. In addition, since the image image has 255 types of gradations other than white, if the image has gradations 1 to 16, a dot pattern (6A
), if the image has gradation levels 17 to 32, a dot pattern with a black 2-dot character image buffer (6th B
Similarly, as in the dot patterns shown in FIGS. 6C to 6F, by processing up to 255 gradations, 255 gradations are expressed in a way similar to 16 gradations. Note that the explanation for gradations 65 to 224 is clear from the above explanation, so
Omitted.

Here, as an example of drawing a figure only inside the character boundary, the image pixel 34 shown in FIG.
In the case of 240 (15 dots are black), the pattern shown in FIG. 6E is selected. If image pixel 34 is clipped downward at a character boundary, as in the example shown in FIG. 5, the dot pattern shown in FIG. 6E is stored in character image memory 4 as the dot pattern shown at 62.

Here, the above operation will be specifically explained.

FIG. 7 is a flowchart illustrating the process (step S4) when image pixels straddle character boundaries according to this embodiment.

First, in step SIO, the gradation of the image pixel is “゜O
” or ゜゜1゛゜ or more.

As a result, if it is "O", there is no need to draw, so this process ends.In addition, in step Sll, the gradation is l.
~l6, i.e., the pattern shown in FIG. 6A described above (
A determination is made as to whether it corresponds to gradations 1 to 16). As a result, if the gradation is between 1 and l6, the process proceeds to step S12, and if the 1 dot to be made black is inside the character boundary, the corresponding dot in the character image memory 4 is set to 1 dot black. . Also, the gradation is 17 to 32 or the gradation is 33 to 48.
In each case, when the two dots to be black are inside the character boundary, the corresponding dots in the character image memory 4 are set to two black dots (steps S13 and S14).
, when the three dots to be black are inside the character boundary, the corresponding three dots are set to black (step S15, step SS16). Note that since the dots are blackened only on the inside of the character boundaries, a maximum of one dot is blackened in step S12, a maximum of two dots is blackened in step S14, and a maximum of three dots are blackened in step S16. Similarly, the gradation ranges from 225 to 240 depending on the gradation of the image pixel.
As a result, for example, at gradation levels 225 to 240, a maximum of 1155 dots are black, depending on the dot position and number of dots in character pixel units that exist inside the character boundary. At gradations 241 to 255, a maximum of 16 dots are set to black according to the dot position and number of dots in character pixel units existing inside the character boundary.

In this way, data with different resolutions are independently and accurately and efficiently stored in the character image memory 4 and the image image memory 5.
By inputting both data from 5 through the corresponding video signal lines 8 and 9, processing for superimposing characters on the image, processing for cutting out the inside of the image into the shape of characters, and processing for converting the image into the outline of the characters are performed. Processing such as hollowing out can be carried out well.

As described above, according to this embodiment, a high-quality output image can be obtained by combining buffers with different resolutions.

In other words, being able to combine 16 buffers with different resolutions can save memory capacity and reduce manufacturing and product costs.

Now, in the above-mentioned embodiment, an example was shown in which an image is written inside a character, but the present invention is not limited to this. Needless to say, various applications such as extraction are possible.

Furthermore, although two types of buffers were synthesized, the invention is not limited to two types.

Furthermore, in the above-described embodiment, the processing is performed separately for the character image buffer and the image image buffer, but the present invention is not limited to this, and the buffers may be classified according to the type of image. .

For example, lines drawn by vector graphics may be processed with a high-resolution buffer, and vector graphics figures with gradation may be processed with a low-resolution, high-gradation buffer.

In addition, in the embodiment described above, two types of buffers are rOR
However, the present invention is not limited to this, and as long as it does not depart from the spirit of the present invention, rOR writing may be used.
However, various modifications can be made depending on how the circuit is assembled.

[Effects of the Invention] As explained above, according to the present invention, a high-quality output image can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the image forming apparatus of the present invention, FIG. 2 is a diagram illustrating the difference in size between image pixels and character pixels according to this embodiment, and FIG. 3 is a diagram showing this embodiment. 4 is a flowchart explaining the image processing operation according to this embodiment. FIGS. 5 and 6A to 6F are black dots according to the gradation of image pixels according to this embodiment. FIG. 7 is a flowchart illustrating processing when image pixels straddle character boundaries according to this embodiment. In the figure, 1...Printer, 3...CPU, 4...Character image memory, 5...Image image memory, 6...
Program ROM. 7...RAM, 8,9...video signal line, 10...output section, 20...host computer, 21...image pixel, 22...character pixel, 31,31°... -Character boundary, 34.33...image pixel, 62...dot pattern.

Claims (3)

[Claims] (1) In an image forming apparatus, an input means for inputting image data having gradation and resolution attributes, and determining a dot pattern at a gradation lower than the gradation based on the gradation of the input image data. determining means for storing the determined dot pattern based on the resolution attribute of the input image data, dividing it into low resolution or high resolution; An image forming apparatus comprising: a forming means for forming an image. (2) The determining means has a plurality of dot patterns depending on the gradation, and has a discriminating means for determining one dot pattern based on the gradation of the input image data. The image forming apparatus according to claim 1. (3) The image according to claim 1, wherein the storage means has a first memory that stores a low-resolution dot pattern and a second memory that stores a high-resolution dot pattern. Forming device.