Facsimile and static presentation processing – Static presentation processing – Size – resolution – or scale control
Reexamination Certificate
2000-01-19
2004-04-06
Coles, Edward (Department: 2622)
Facsimile and static presentation processing
Static presentation processing
Size, resolution, or scale control
C358S001100, C358S001200, C358S001500, C358S001600, C358S001800, C358S001900, C382S194000, C382S298000, C382S299000, C382S303000
Reexamination Certificate
active
06717695
ABSTRACT:
FIELD OF THE INVENTION
The invention is directed to a method for processing image data, particularly in printer, whereby a source image to be processed contains source picture elements arranged matrix-like to which a respective source image datum is allocated, this determining the presentation of the respective source picture element. A target image arising in the further-processing of the source image data contains target picture elements arranged matrix-like to which a respective target image datum is allocated, this defining the presentation of the respective target picture element.
Such methods are called scaling methods and are utilized, for example, in printers when target image data of a print image or, respectively, target image are produced from the source image data of a source image, said target image being expanded or compressed in line direction compared to the source image or, respectively, having a higher or lower resolution in line direction than the source image. A scaling factor thereby indicates the ratio between target image resolution and source image resolution in a specific image direction.
When, for example, scaling is carried out line-by-line, then a line factor is prescribed as scaling factor that defines the ratio of the number of line picture elements per line of the target image relative to the number of source picture elements per line of the source image. The line factor sometimes has a value that is not a whole number. When a target image having a resolution of 600 dpi in line direction is to be produced from a source image having a resolution of 240 dpi (picture elements per 25.4 mm) in line direction, then the line factor has, for example, the value 2.5. The line factor likewise has the value 2.5 when, given the same size of the source picture elements and the target picture elements, a target image is to be produced from the source image whose extent in line direction amounts to 2.5 times the value of the extent of the source image in line direction. In other words, the source image is stretched by the factor 2.5 in line direction.
The line factor is less than 1 when a target image having reduced resolution in line direction is produced from the source image or when the target image is compressed in sine direction compared to the source image.
BACKGROUND OF THE INVENTION
A method that implements a transformation of the locus coordinates between source image and target image is known, for example, for generating the target data. In this method, however, a plurality of multiplications and similar operations are implemented that require a plurality of processor clocks.
U.S. Pat. No. 4,275,450 discloses a method and a circuit arrangement for enlarging or reducing images wherein the image data are selectively sluiced through a plurality of processing stages.
DE 34 18 624 C2 discloses a scaling method wherein image data are converted line-by-line from a first raster into a second raster having different resolution. For demagnifying images (scaling factor<1), an initial value (for example, 5/16) is first set in an address counter, and the counter is incremented by a specific value (for example 5/8) with each processing step. Whenever the address counter exceeds a comparison value (for example 1), the current image datum is transferred into a buffer memory. The comparison value is thereby higher than the initial value. What is disadvantageous about this type of scaling is that the outermost picture elements at the image edges—particularly the first picture element at the beginning of the line—are suppressed because the initial value (5/8) is lower than the comparison value. This leads to image falsifications; in particular, edge lines having a width of one picture are not reproduced in the target image.
SUMMARY OF THE INVENTION
An object of the invention is to achieve a high processing speed and a true-to-the-original reproduction in the target image when scaling image data.
This object is inventively achieved by a procedure having the features of patent claims
1
,
2
,
4
and
15
as well as by a circuit arrangement having the features of patent claim
13
. Advantageous embodiments of the invention are recited in the subclaims.
According to the invention, a scaling variable is cyclically compared to a comparison value and, dependent on the comparison result, a decision is made as to whether a source image datum is accepted as target image datum. One thereby proceeds from a start value that is defined such that the first source picture datum is respectively accepted as target image datum under a predetermined comparison criterion in a group of source image data, for instance in an image row or in an image column.
When a source image datum has been taken as target image datum, the scaling variable is either added or subtracted by a constant value, particularly by the value one. When a source image data was not accepted as target image datum, the scaling variable is either subtracted or added by the scaling factor. The subtraction or, respectively, additions in both instances of the transfer behave mutually in the invention; when subtraction is carried out in the case of the data transfer, then adding is carried out in the case of non-transfer and vice versa.
In a preferred embodiment of the invention, the start value is identical to the scaling factor, the comparison value is zero, the value one is employed as constant and this is cyclically subtracted from the scaling variable. In another preferred embodiment of the invention, the start value is identical to the scaling factor, the comparison value is zero, the value one is employed as constant, and this is cyclically added to the scaling variable.
The invention is based on the consideration that the production of the target image is especially simple when only addition and subtraction operations are employed insofar as possible upon implementation of the method or, respectively, calculating operations whose execution requires only one clock or only a few clocks in a digital circuit arrangement. Particularly in a printer, the image data are successively transmitted to a print head. The method must therefore be designed such that an additional intermediate storage of the image data is avoided.
A high processing speed is achieved by assigning a scaling factor and by the following, cyclical processing of the source image data. In that a value whereat the first image datum is accepted is prescribed as start value, for example the first source image data of a row or column as first target image datum, the picture elements of the image lying at the start are correctly reproduced in any case, namely independently of the specific scaling factor (expansion or compression). Given an expansion of the image, at least the two first picture elements of a row or, respectively, the first two rows of an image are transferred into the target image data. The reproduction veracity in these edge regions is therefore significantly improved to the aforementioned and known methods. This advantage is particularly felt given graphic edge lines of images.
The invention is particularly suited for employment in a hard-wired, electronic circuit or in a user-specific integrated circuit (ASIC). A pipeline structure is particularly advantageous given such a circuit, the source image data being loaded therein from a first memory via a first data line into a control circuit for the execution of calculations and comparisons, and the calculated, target image data being deposited in a following, second memory. The second memory is connected to the control circuit via a second line that is separate from the first line. This arrangement allows a high processing speed because the loading and storing of the source or, respectively, target image data can ensue parallel in time.
Given a line-by-line, cyclical image data processing according to the invention, the source image data for successive source picture elements of at least one line of the source image are successively processed. The scaling factor here indicates the ratio of the n
Coles Edward
Oce Printing Systems GmbH
Sanbet Zebene
Schiff & Hardin LLP
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