Abstract:
A pre-printing toner-save method for selective, different-character Page Description Language (PDL) color-object rendering of different-category PDL color objects. This method includes (1) a preliminary determination regarding whether such an object is categorizable as a text object, as a graphics object, or as a raster object, and (2) a subsequent, “post categorization” evaluation of whether the specific-category object nominally selected for toner-save treatment possesses a certain preselected threshold characteristic (or characteristics). Objects so categorized and “successfully thresholded” are then subjected to differentiation into different object regions (edge and non-edge), and then to toner-save rendering which includes the two, collaborative steps of (a) preserving object-edge dot density, and (b), within an object&#39;s bounding edge, establishing a checkerboard pattern of dots which maximizes dot gain.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
       [0001]     This invention pertains to color object (or image) rendering for toner-save printing, and more specifically, to a method for enabling and producing selective, different-character color-object rendering with respect to different-category Page Description Language (PDL) color objects. Hereinafter, the term “image” will be used interchangeably with the term “object”. They will be treated as being synonymous.  
         [0002]     Actual implementation of toner-save rendering, in accordance with the invention, is based, from one point of view, upon the specific category of such an object, and within each such category, further upon the presence of a particular object-threshold object characteristic. From another point of view, the invention involves selecting a PDL color object for toner-save rendering, distinguishing edge-boundary regions from other regions in the selected object, and then applying different region-specific toner-save rendering modalities. These two modalities include (a) an edge pixel density preservation modality, and (b) a checkerboarding pixel dot-gain maximizing modality.  
         [0003]     In the description of the invention herein, three specific categories of PDL color images are addressed. One of these categories involves a text (font) image, another involves a graphics (vector object) image, and the third involves a raster image (typically rectangular in shape). With respect to a text-category image, font size is employed as a threshold determiner for whether or not toner-save rendering is to be employed. With regard to a graphics-category image, the operative threshold respecting whether or not to utilize toner-save printing involves the existence in the image of a predetermined combination of image pixel width and image pixel height. In the case of a raster-category image, the categorical determination associated with that image, namely, that it is a raster image, also functions as the operative threshold for determining whether or not to employ toner-save printing.  
         [0004]     Where a toner-save method of rendering is selected for pre-printing implementation by a user, and where the relevant image, or object, threshold is met, such rendering, in accordance with the practice of the invention, includes two steps. One of these steps involves preserving image-edge dot density, and the other step involves establishing a checkerboard, dot-gain-maximizing pattern of dots to be employed within the edge boundary of an image. A further consideration, and practice, is that toner-save rendering, when selected and implemented, is always practiced in what is known to those skilled in the art as a bi-tonal mode of operation.  
         [0005]     Practice of the present invention offers a significant improvement over prior art toner-save methods in relation to preserving rendered image resolution and overall image quality.  
         [0006]     The various features and advantages which are offered by the invention, and which make possible the just-stated improvement in color-image (color-object) rendering, will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a high-level, block/schematic diagram illustrating a preferred embodiment and manner of practicing the toner-save, color-image rendering steps of the present invention.  
         [0008]      FIG. 2  is a fragmentary block/schematic diagram generally illustrating steps that are involved, in accordance with the practice of the invention, to implement toner-save rendering.  
         [0009]      FIG. 3  is a more detailed block/schematic diagram which provides a more specific picture of the structure and methodology shown more generally in  FIG. 1 .  
         [0010]      FIG. 4  presents a visual representation of a color image which has been toner-save rendered in accordance with preferred practice of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]     Turning now to the drawings, and beginning with  FIGS. 1 and 2 , indicated generally at  10  in  FIG. 1 , in block/schematic form, is an illustration of both the preferred methodology, and the preferred general structural organization, of the system and practice of the present invention. From the description which now follows, when read in conjunction with these and the other two drawing figures, those generally skilled in the relevant art will know clearly how to implement and practice the invention.  
         [0012]     Included in system and methodology  10  (reference hereinafter will be made more specifically to methodology), as shown in  FIG. 1 , are two diamond-shaped blocks  12 ,  14 , and four rectangular blocks  16 ,  18 ,  20 ,  22 . Appropriately shown interconnecting these several blocks are arrow-headed lines which generally picture the operational flow that is implemented by methodology  10 .  
         [0013]     Block  12 , marked “TONER-SAVE?”, asks, as on a user-interface display screen, a question of a user preparing to call for printing of a PDL color image (object). This question asks whether that user wishes (Yes/No) to call for toner-save color rendering of an image selected for printing. The (Yes/No) paths out of block  20  are clearly illustrated in  FIG. 1 , with the “Yes” path leading to block  16 , marked “IMAGE CATEGORY”, and the “No” path leading to block  20 , marked “REGULAR RENDERING”. Block  12  thus represents an opportunity for a user of the methodology of this invention to make a specific “Yes/No” selection regarding implementation or non-implementation of toner-save color-image rendering.  
         [0014]     If a “No” selection is made, whatever the image is is simply treated in block  20  to regular, conventional rendering, and is then passed along from block  20  to block  22  which is labeled “TO PRINTING”.  
         [0015]     If the answer posed to the question presented in accordance with block  12  is “Yes”, then control effectively passes to block  16  which obtains information (see arrow  24  in  FIG. 1 ) from the relevant imaging system (not part of this invention) which describes the nature, or category, of PDL image, or object, that has been selected for toner-save rendering. In this context, there are three high-level general categories of imagery (objects) which are specifically addressed by the present invention. These three categories include (a) text imagery, (b) graphics imagery, (c) and raster imagery. Thus, in block  16 , after a “Yes” toner-save decision has occurred, the first image-related determination which takes place by operation of the invention is the category of the image respecting which toner-save rendering is to take place. Previously mentioned arrow  24 , which points toward the right side of block  16  in  FIG. 1 , represents the presentation of image-category information from the relevant PDL imaging-system interpreter regarding the specific category of imagery just mentioned.  
         [0016]     From block  16 , control is handed to block  14 , labeled “TS RENDERING?”. This block essentially asks the next question, which is whether or not the categorically specific image that has been identified by block  16 , possesses certain predetermined imagery characteristics (a threshold) which make it suitable for tone-save rendering. In other words, because of this thresholding consideration, not necessarily are all images actually subjected to toner-save rendering. Rather, and in order that the system and methodology of this invention will operate most efficiently and effectively, a further image-specific determination is made in order to confirm whether or not toner-save rendering is actually to take place. This thresholding practices separates images with regard to which toner-save rendering is unnecessary and/or inappropriate.  
         [0017]     With regard to text imagery, font size is employed as a threshold determiner regarding whether or not a particular text image is to be presented for toner-save rendering. Clearly, and as will be recognized by those generally skilled in the relevant art, what this toner size specifically is is a matter of user/system-designer choice. In the preferred implementation of methodology  10  now being described herein, the font-size threshold level which has been selected is font-size- 12 .  
         [0018]     With regard to graphics imagery, the threshold determiner involves an assessment of both image pixel height and image pixel width. While these two pixel dimensions may be different in number if desired, in most instances it has been found to be preferable to employ like size numbers for both of these dimensions. In the preferred embodiment of the invention now being described, the pixel height and pixel width numbers are the same, and are set at the level of 8-pixels.  
         [0019]     With respect to a raster image, that categorical determination alone is employed, without any additional threshold questioning, to determine that such an image is indeed appropriate for toner-save rendering.  
         [0020]     A point which should be made here regarding what occurs when the question presented by block  12  is answered in the affirmative is that the related imaging system is placed in a condition for performing any actually implemented toner-save rendering in a bi-tonal mode of operation. Those skilled in the art will immediately recognize the significance of this selection, and also how it may be implemented.  
         [0021]     With respect to the operation of block  14 , if a particular image which has been reviewed has characteristics that lead to a “Yes” answer emerging from block  14 , control passes to block  18 , labeled “TONER-SAVE RENDERING”. Block  18  performs toner-save rendering, as will shortly be described, and passes rendered imagery data to block  22  for ultimate printing. If an image being reviewed for toner-save rendering results in a “No” answer emerging from block  14 , that image is passed directly to block  20  for regular rendering, after which, such rendered image data is passed to block  22  for printing.  
         [0022]     Turning attention now more specifically to  FIG. 2 , this fragmentary block/schematic diagram presents a somewhat more detailed picture of previously described toner-save rendering block  18  shown in  FIG. 1 . In accordance with practice of the present invention, toner-save rendering fundamentally involves two steps which are represented in  FIG. 2  by two blocks,  26 ,  28 .  
         [0023]     The step represented by block  26 , labeled “PRESERVE EDGE DENSITY”, involves a decision not to make any change in current pixel edge density (a preserving pixel edge density modality). Thus, for all of the categories of imagery which are to be subjected to toner-save printing, all will be treated in exactly this fashion with respect to the preservation of edge density in the region of an object&#39;s edge.  
         [0024]     The other step is represented by block  28 , labeled “MAXIMIZE DOT GAIN”. This step of the invention relates to pixel content in the region within an image&#39;s bounding edge. Fundamentally what is implemented here is the rendering of an image so as to create, within the image&#39;s edge, or boundary, a pixel distribution which is checkerboard-like in nature, and which, when implemented appropriately, results in the inside region of an image displaying what is known in the art as maximum pixel dot gain. This concept of maximum pixel dot gain is well known to those skilled in the art, and needs no elaboration here. This rendering practice is referred to herein as a checkerboarding dot-gain maximizing modality.  
         [0025]     Completion of the activities represented by blocks  26 ,  28  in  FIG. 2  effects the desired and requested color-image toner-save rendering in accordance with practice of the invention.  
         [0026]     Before turning specific attention to  FIG. 4  in the drawings which presents a representative image that has been toner-save rendered, let us turn attention for a moment to  FIG. 3  which, effectively, illustrates in greater detail that which is shown in  FIGS. 1 and 2 . Included in the illustration presented in  FIG. 3  are three diamond-shaped blocks  30 ,  32 ,  34 , and twelve rectangular blocks  36 - 58  (even numbers only), inclusive. A comparative viewing of  FIGS. 1, 2  and  3  will make readily apparent to those skilled in the art how the components shown in  FIG. 3  relate to those which are pictured in  FIGS. 1 and 2 .  
         [0027]     As illustrated in  FIG. 3 , block  36  represents the start of an implementation of the methodology of the invention, and block  30  represents, essentially, the same as that which is represented by block  12  in  FIG. 1 . If a user elects to use toner-save rendering, control passes to block  38 , and if not, control passes to block  40 . Block  38  effectively places the relevant imaging system in a condition ready for bi-tonal modal operation with respect to any implemented toner-save rendering. Next, blocks  42 ,  44 ,  46  (which combinedly are represented by single block  16  in  FIG. 1 ), assess the category, among the three mentioned earlier, of color imagery which is to be rendered. If control, instead of being handed to block  38 , goes to block  40 , then conventional, regular rendering of a particular image takes place, and the rendered result is sent to block  58  which is the same, effectively, as block  22  in  FIG. 1 .  
         [0028]     Diamond blocks  32 ,  34  are referred to herein as thresholding blocks, and represent the determinations which are performed, as earlier mentioned, with respect to assessing threshold characteristics of text and graphics images, respectively. The functionalities of these blocks are represented collectively in  FIG. 1  within block  14 . No such diamond-shape thresholding block is employed on the downstream side of block  46 , inasmuch as the categorical determination that a raster image is to be rendered is all that needs to occur in order for toner-save rendering to be implemented for such an image.  
         [0029]     With regard to a text image, if the threshold font size characteristic is appropriate, toner-save rendering is implemented in block  48 , and the rendered result is passed to block  58 . If the text font size threshold is not met, the image is passed for rendering in a regular fashion within block  50 , and from this block, rendered data is passed to print block  58 .  
         [0030]     With respect to a graphics image, a “Yes” answer with respect to image characteristics related to pixel height and pixel width dimensions causes control to pass through block  52  for toner-save rendering, and thence to print block  58 . If either the height or the width threshold level is not met by a particular reviewed graphics image, rendering is performed in a normal, non-toner-save manner within block  54 , with the “normally” rendered image data then being passed to print block  58 .  
         [0031]     A raster image is simply automatically toner-save rendered as illustrated by block  56  in  FIG. 3 . This toner-save rendered raster image is then passed along to print block  58 .  
         [0032]     It should be apparent that blocks  40 ,  50  and  54  in  FIG. 3  are represented by singular block  20  in  FIG. 1 . Similarly, it should be apparent that blocks  48 ,  52 ,  56  in  FIG. 3  are represented by singular block  18  in  FIG. 1 . With respect to the activities which are effected by toner-save rendering blocks  48 ,  52 ,  56  in  FIG. 3 , these activities are implemented in blocks  26 ,  28  in  FIG. 2 .  
         [0033]     Turning attention now to  FIG. 4  in the drawings, illustrated in this figure, in a row-and-column fashion at  60 , is a representative image which is has been toner-save rendered in accordance with practice of the present invention. Image  60  is employed herein to illustrate practice of the invention with respect to each of the three categories of PDL images mentioned earlier, namely, text images, graphics images, and raster images. It will be assumed for the purpose of this description that image  60 , with respect to its representation of a text image, is characterized with a font size of at least  12 . With respect to thinking of image  60  as relating to a graphic image, one can see that the image shown here in  FIG. 4  has a pixel height of 8-pixels as well as a pixel width of 8-pixels. Thus, what is shown in  FIG. 4  meets the minimum threshold requirements for the implementation of toner-save rendering for both text and graphics images. Thinking about image  60  as representing a raster image, that determination alone is sufficient to determine that toner-save rendering is appropriate.  
         [0034]     Image  60 , as mentioned above, is shown in a toner-save rendered condition. What will be noticed, therefore, about this thus-rendered image, is that edge density, shown generally at  62 , has been preserved to form a continuous, bounding pixel edge  62 . Within this preserved-density, bounding edge is a central pattern  64  which is checkerboarded in nature, and which very specifically, is checkerboarded in a manner which produces maximum pixel dot gain.  
         [0035]     The invention thus proposes a unique, quite simply implemented, and very effective toner-save method which may be employed with regard to PDL text, graphics and raster color images, or objects. Where toner-save rendering is selected to be employed, once an image to be considered for toner-save rendering has been determined to pass all of the thresholding tests necessary, that image is toner-save rendered in a manner whereby pixel edge-region density is preserved, and central regions of the image are prepared with a maximized dot gain checkerboard pattern.  
         [0036]     Accordingly, while a preferred embodiment and manner of practicing the invention have been described herein, it is appreciated that variations and modifications may be made therein without departing from the spirit of the invention, and it is intended that all claims to invention herein will cover such variations and modifications.