Patent Application
20070182972
1. Field of the Invention
The present invention relates to an image processing method and system, particularly to image processing method and system for using in a printer having an asymmetrical-resolution.
2. Description of the Prior Art
Generally speaking, before actual print-out, a printer has to do some pre-print processing known as halftoning to assimilate and convert the image data it has just received. There are two kinds of halftoning techniques related to this preprinting process: AM (Amplitude Modulation) and FM (Frequency Modulation). With the AM technique, the size of printer toner dots varies with the tone of the image, whereas with the FM technique, the dot size is fixed, it is the varied spacing between the dots that decides the tone of the image. The AM technique is generally used with laser printers, while the FM technique is used with ink jet printers.
An image is thus constituted by a plurality of densely clustered pixels, each pixel having a corresponding gray scale value ranging from 0 to 255.
Halftoning is done by converting the data contained in each pixel of the image according to a halftone table, formed by the directional characteristics of the four printing colors: CM
Y
K, which is a prior art technique of which we will not make more description than is necessary.
To illustrate, the following is a table which contains all the data corresponding to an image. Each grid represents a pixel and its corresponding gray scale value.
Table 2 is a symmetric resolution halftone table containing a plurality of corresponding values.
By comparing the corresponding grids of Table 1 with those of Table 2, we obtain Table 3. When the grey scale value of a grid in Table 1 is smaller than the halftone value in the corresponding grid of Table 2, the corresponding grid of Table 3 is assigned a value of 0. When the grey scale value of a grid in Table 1 is lager than the halftone value in the corresponding grid of Table 2, the corresponding grid of Table 3 is assigned a value of 1. Thus, values in Table 3, from top left to bottom right, will run as follows: 0(32<50), 1 (25>3), 0 (100<101) . . . and so on.
The printer will, according to the value received being 0 or 1, decide to print or not to print, hence forming the picture to be printed.
Please refer to
However, most printers nowadays are printers with such asymmetrical resolution as 1200*600 dpi, 2400*600 dpi, etc., If such printers use the aforesaid symmetrical resolution halftone table for pre-print processing, the printed result will be as
The purpose of this invention is thus to provide an image processing method and system for asymmetrical resolution printers so that the above problem may be solved.
The purpose of the present invention is to provide an image processing method and system for a printer with asymmetrical-resolution to print out quality images.
The present invention relates to a set of image processing systems used in printers with asymmetrical resolution; the data received by the printer is halftoned according to a table so as to print out the corresponding images. The aforementioned asymmetrical-resolution has an aspect ratio of n=X:Y, with X being the width of the windows and Y being the height of the windows t, and the aforementioned pre-print processing, the halftoning process, is to be used with the AM(Amplitude Modulation) techniques of laser printers. Also, the image processing comprises a computation/conversion module.
Referring to a halftone table, the computation/conversion module will, by making use of an algorithm, expand the image's corresponding data on the symmetrical-resolution halftone table along width direction by n times, and, hence, acquire the desired asymmetrical-resolution halftone table.
The asymmetrical-resolution printer then goes on to do the pre-print processing of halftoning according to the asymmetrical-resolution halftone table so as to print out ideal images.
One more thing to add: the image processing system comprises a placement module, whose function is to distribute a plurality of densely clustered symmetrical-resolution halftone table over an image data's corresponding part in the image.
Subsequently, the module picks up from those symmetrical-resolution halftone tables a symmetrical-resolution halftone table as a chosen symmetrical-resolution halftone table as well as those symmetrical-resolution halftone tables around this chosen symmetrical-resolution halftone table, which the computation/conversion module will then use the aforementioned algorithm to expand into asymmetrical-resolution halftone tables.
The algorithm described above can be an interpolation such as a B-spline method or the like. The computation/conversion module first picks up from the chosen symmetrical-resolution halftone table two neighboring pixels, get an average value out of the two pixels' grayscale value, and then interpolate the value between the two pixels.
Thus, according to an image processing system and method for asymmetrical-resolution printers of the present invention, the printer's system can properly convert symmetrical-resolution halftone tables into asymmetrical-resolution halftone tables, which the system will use to do the pre-print processing so as to print out ideal images.
The following detailed descriptions and drawings will further illustrate the features and benefits of the present invention.
Please refer to
The pre-print processing of halftoning as mentioned in the above is of the AM (Amplitude Modulation) type, a technique generally used with laser printers. The image processing system 32 comprises a placement module 42 and a computation/conversion module 44.
The system first picks up a symmetrical-resolution halftone table 52, as
Subsequently, the module picks up from those symmetrical-resolution halftone tables a symmetrical-resolution halftone table as a chosen symmetrical-resolution halftone table 5202 as well as those symmetrical-resolution halftone tables 52 (altogether 8 in number) around this chosen symmetrical-resolution halftone table.
Next, the computation/conversion module 44 will, by making use of an algorithm, expand the image's corresponding data on the chosen symmetrical-resolution halftone table 5202 along width direction by n times, and, hence, acquire a desired asymmetrical-resolution halftone table 54.
The asymmetrical-resolution printer then goes on to do the pre-print processing of halftoning according to the asymmetrical-resolution halftone table 54 so as to print out ideal images.
The algorithm described above can be an interpolation. The computation/conversion module first picks up from the chosen symmetrical-resolution halftone table 5202 two neighboring pixels, get an average value out of the two pixels' grayscale value, and then interpolate the value between the two pixels. The algorithm can be a B-spline method, too.
The following is an example illustrating the B-spline interpolation method which works with a 5×5 symmetrical-resolution halftone table. Table 4 is the symmetrical-resolution halftone table.
Converting Table 4 into an asymmetrical resolution halftone table (10×5), we get Table 5.
Please refer to
Step S02: Pick up a symmetrical-resolution halftone table 52
Step S04: Distribute a plurality of densely clustered symmetrical-resolution halftone table 52 (arranged in dot matrices) over an image data's corresponding part in the image 60, and then choose one of them as a default symmetrical-resolution and them picks up it as well as eight neighbor symmetrical-resolution halftone tables 52 thereof.
Step S06: By making use of an algorithm, such as an interpolation. A B-spline is one kind of interpolations, which expand the chosen symmetrical-resolution halftone table 5202 along width direction of the data's corresponding image by n times in order to acquire the desired asymmetrical-resolution halftone table 54.
Step S08: By making use of the asymmetrical-resolution halftone table 54, the system then goes on to do the pre-print processing of halftoning on the image data for the subsequent print out.
Thus, by means of asymmetrical-resolution printer image processing system 32 and image processing method of the present invention, the symmetrical-resolution halftone table 52 is properly converted to the asymmetrical-resolution halftone table 54, by which the printer can do the necessary pre-print processing of halftoning in order to print out quality images.
As is understood by a person skilled in the art, the foregoing preferred embodiment of the present invention is an illustration, rather than a limiting description, of the present invention. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures.
