Computer graphics processing and selective visual display system – Computer graphics processing – Shape generating
Reexamination Certificate
1998-06-29
2001-03-13
Brier, Jeffery (Department: 2672)
Computer graphics processing and selective visual display system
Computer graphics processing
Shape generating
C345S440000, C345S441000
Reexamination Certificate
active
06201550
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to an image forming apparatus for forming image information by executing image drawing commands, and more particularly relates to an image forming apparatus capable of effectively describing and reproducing a drawn graphics image using a gradation pattern whose colors are progressively changed, and a method of generating a gradation pattern.
Heretofore, as document composition systems and document print systems using computer systems are sophisticated, representation techniques used therein are also sophisticated. In order to execute the effective presentation and the solid geometric representation, there has been used a technique called gradation for progressively changing a color of a certain graphics image area.
While a document composition software is able to designate gradation by using a variety of user interfaces, this imposes a large load on the printer side when the printer prints the gradation. The reason for this is that a page description language for describing document data is unable to effectively describe the gradation. As a result, to realize the gradation, a page description language is described by the procedure in which regions of the same shape but having slightly different colors are drawn in an overlapping fashion with each other with slight displacements. For example, in a gradation in which colors are changed smoothly in a concentric circle fashion, it is necessary to repeatedly execute the processing in which a large circle is drawn and filled with a pattern and a little smaller circle is drawn on the above circle with a different color in an overlapping fashion and then filled with a pattern until the position reaches the center position of the circle. Thus, when the page description language processing system generates the gradation pattern, it is unavoidable that the complicated procedure should be executed, thereby resulting in the processing load being increased.
On the other hand, Japanese Published Unexamined Patent Application No. Hei 8-72317 describes a method of realizing a gradation on the printer side. This method introduces a gradation description as a part of description method of a page description language. When this page description is interpreted, the gradation pattern expanded as the background is cut out by the shape of the drawing target graphic form, thereby resulting in the gradation within the printer being realized. Also, according to this method, in order to draw a gradation of a circumference shape, a boundary of very small concentric circle-shaped regions is calculated by using a DDA (digital differential algorithm). DDA is a well-known algorithm for computing a position at which an intersection point of a graphic form crossing a certain scanning line is moved on the next scanning line. By using this algorithm, all intersection points with the scanning line are computed previously and the filling processing between the intersection points is executed.
However, in accordance with the method described in Japanese Published Unexamined Patent Application No. Hei 8-72317, since the gradation pattern larger than the graphic form shape is one expanded and cut out along the graphic form shape, it is necessary to compute colors of other regions than the drawing target region. Moreover, in the case of the gradation of the concentric circle shape, the proceeding direction of the computation is directed in the boundary of the concentric circle-shape region, which processing is not suitable for the filling processing on the scanning line. There is then the problem that independent processing steps are required.
SUMMARY OF THE INVENTION
In view of the aforesaid aspect, it is an object of the present invention to provide an image forming apparatus and a gradation drawing method in which a load for drawing a gradation may be alleviated.
Furthermore, in the image forming apparatus according to the present invention, when the generation of the gradation is instructed as the image drawing command, the drawing means accesses the gradation generating means. In that case, the drawing means transfers coordinate values of two points, namely vector start point and end point on the drawing plane on the drawing plane and color values of said start point and said end point, as gradation information for designating a gradation pattern. The gradation generating means expresses a gradation pattern whose color value is progressively changed along a straight line in a plurality of adjacent band-like regions perpendicular to the straight line connecting the start point with the end point and in which color values therein become uniform by using the gradation information, and generates gradation patterns of respective scanning lines by successively specifying portions included in each band-like region of the scanning line direction in a drawing region for drawing a gradation pattern of respective scanning line. Then, the gradation pattern is generated by executing this processing on each scanning line. Furthermore, this is also true in the gradation pattern generation method of the present invention. At every scanning line, the gradation pattern is generated in the direction of the scanning line.
Since the gradation pattern is generated at every scanning line as described above, a large gradation pattern need not be previously generated in the background unlike the prior art. Thus, a memory amount and a processing time may be reduced considerably. Furthermore, by advancing the processing in the scanning line direction, this processing may be matched with other drawing processing than the gradation processing in which the processing is executed at the unit of the scanning line.
According to an aspect of the present invention, there is provided an image forming apparatus for obtaining an output image by executing image drawing commands. This image forming apparatus is comprised of command analysis means for analyzing an inputted print job and generating a drawing command and drawing data which becomes parameters of the drawing command, drawing means for executing a drawing processing in accordance with the drawing command analyzed by the command analysis means, drawing data storage means for storing the drawing data, and gradation pattern expansion means accessed by the drawing means when gradation of a concentric circle shape is drawn, which expands a gradation pattern with respect to all scanning lines crossing the drawing region based on gradation information stored in the drawing data storage means.
According to the image forming apparatus, the command analysis means analyzes drawing data at the two points on the drawing plane and drawing data for drawing the gradation in which colors at the respective points are designated and stored in the drawing data storage means. When the drawing command for drawing the gradation is analyzed by the command analysis means, the analyzed drawing command is supplied to the drawing means, and the drawing means expands the gradation pattern by using the gradation pattern expansion means. At that time, the gradation pattern expansion means refers to the drawing data storage means, calculates based on the color designated by the drawing data and the coordinate values a color at the position in which the scanning line and the boundary of the drawing region cross each other, and repeats an operation in which the next color change position is calculated to the end of the drawing region, thereby calculating a sequence of pixels expressing changing colors in the sequential order within the drawing region. This processing is applied to all scanning lines crossing the drawing region, thereby generating the gradation pattern. Here, the shapes of the very small intervals with uniform color comprising the gradation pattern may be shapes of concentric circle and widths of the respective very small intervals need not always be made equal.
Further, according to the present invention, there is provided a gradation pattern drawing method for obtaining a gradation output i
Brier Jeffery
Chung Daniel J
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
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