Printing of documents from a computer

Abstract: A method of printing a document from a computer with a printer is provided, together with a computer 8 and a printer 9 adapted to perform necessary steps of the method. The printer 9 has a printer processor 4. The method comprises generating 1 in the computer 8 instruction data (such as page description language) to enable the printer 9 to print the document, generating in the computer 8 resource information 31 indicative of printer processor resources required by the printer 9 at different stages of printing the document, and sending the instruction data and the resource information from the computer 8 to the printer 9. The printer processor 4 is adapted to schedule printer processor resources for the different stages of printing the document in accordance with the resource information, and printing the document with the printer processor resources as scheduled. Advantageously, the resource information is provided as comments in the page description language, located for example in page headers. This mechanism allows the printer to learn in advance of receiving pages of a job how its resources should be scheduled to prevent printer stalls.

Description: The invention relates to an improved method of printing documents with a printer from a computer, and to apparatus and systems adapted for use of this approach. In particular, the invention relates to more efficient use of processor resources in the printing of documents. A conventional printing process from a computer is rendered schematically in Figure 1. The document is generated on computer 8 - this may be for example a personal computer, a workstation, or substantially any other device with a processor on which documents may be held or processed and which are connectable with a printer for producing a hard copy of the electronically held document. Typically, the document will be generated by an application 1, such as a word processing program or a spreadsheet. The document will generally be provided by the application 1 in a printer independent form 5. This printer independent form of the document 5 is sent to a print driver 2. The print driver 2, which is typically customised to a particular model or make of printer, takes this printer independent form of a document and converts it into a printer specific page description 6 which conforms to the printer's page description language (PDL). The printer driver 2 may also add information about the job (of printing the document), such as for example the number of copies, binding options or duplex options. This job information is provided in a job control language (JCL). In common page description languages such as Postscript (a Registered Trade Mark of Adobe Systems Incorporated), certain job information is mixed into the description of a page, as will be described further below. The printer specific page description 6 (including any job information) is then sent to print spooler 3. The print spooler 3 is a mechanism for handling communication between the computer 8 and the printer 9 which is responsible for printing the print job. The printer specific page description is sent at the appropriate time from the print spooler 3 according to whatever protocols apply to the transport connection 7 between the computer 8 and the printer 9, and is received by the printer processor 4. The printer processor 4 observes the stream of PDL and JCL that it receives from the print spooler 3, and controls the printer to generate printed pages accordingly. It should be noted that certain of the resources associated with the computer (in particular the print spooler 3) may not themselves be a physical part of the computer 8, but instead a part of a computer network to which both the computer 8 and the printer are attached. For convenience, throughout this specification such components associated with the computer and not specifically a part of the printer will be referred to as "of the computer". A difficulty in conventional printing systems of this type is that the demands on the printer processor 4 can be very heavy at certain times, and very light at others. For example, consider a print job in which 1 in every 20 pages require a group of unusual fonts to be synthesised together. This synthesis results in a computational load too great for the printer processor to complete within the time normally allocated to the processing of a single page. If the fonts are not already present (for example, held in a cache on the printer) the result will be that the printer stalls (the paper feed pipeline is halted while the printer processor synthesises the necessary characters, and then restarted thereafter). Such stalls can be very expensive in resource consumption for typical modem printers: such a pipeline may be many pages long, and a printer drum may need to be brought back up to temperature before paper can again be fed through the marking engine of the printer. Such circumstances could lead to a halving of print capacity. Situations of this general type (areas which require high consumption of resources scattered among areas which are not so computationally demanding) are common. A mechanism for improving printer performance has been proposed by Peerless Systems (The Hard Copy Observer, September 1998, page 39) which involves deciding whether to render a page on a personal computer and then send it to the printer in TIFF format as an alternative to sending a page to the printer in the normal manner. This allows particularly complex pages to be processed by the personal computer rather than the printer, balancing the load between the two - however, this means that the overall complexity of print processing increases somewhat (with the personal computer taking on a significant additional processing load). An effective improvement to printer performance is provided, but only by shielding the printer from "difficult" pages. It would be desirable instead to improve the use of processor resources by the printer itself to improve printer processor effectiveness and so prevent stalling and possibly also increase printing speed. This is advantageously achieved by the invention as defined in the appended independent claims. Accordingly, the invention provides a method of printing a document from a computer with a printer, the printer having a printer processor, the method comprising: generating in the computer instruction data to enable the printer to print the document; generating in the computer resource information indicative of printer processor resources required by the printer at different stages of printing the document; sending the instruction data and the resource information from the computer to the printer; scheduling printer processor resources for the different stages of printing the document in accordance with the resource information; and printing the document with the printer processor resources as scheduled. The present inventor has appreciated that the problem of excess computational load on the printer processor can generally be removed by allowing printer processor resources to be scheduled appropriately to the demands of a specific print job. For example, in the case indicated above (of 20 normal pages followed by 1 page with complex characters), a stall could be prevented by allowing the generation of the complex characters over the course of the preceding 20 normal pages. Preferably, the instruction data is provided as PDL and/or JCL and the resource information is provided as annotation to the page description language and/or job control language, and wherein the method comprises after the step of generating resource information the step of annotating the instruction data with the resource information. To enable printer processor resources to be scheduled appropriately, there must be a mechanism by which the printer processor can be provided with information which can provide an indication of the printer processor resources required by the printer at future stages of printing the document. The present inventor has realised that this information is essentially available from the PDL and JCL, although it is not provided by the PDL and JCL in a form which allows the printer processor to schedule its resources in advance. It is however possible either to change the way in which the PDL and JCL are generated, or to add an additional stage at the computer (or possibly elsewhere in a computer network of which the computer is a part) in which the PDL and JCL is filtered for the information which would be needed to determine effective printer processor resource allocation, and for this filtered output to be provided to the printer processor at least in part temporally in advance of the pages to which it relates. The first of these approaches can be realised by modification of the printer driver, and the second by either modification of the print spooler or by adding an extra software package which takes the output of the printer driver, analyses it for resource information and then annotates it accordingly. A particularly effective form of annotation is by comments in the PDL, particularly at the head of each printed page. Different approaches to this are possible, depending on desired system performance: providing all resource information on the first page header; providing resource information as it is generated on the next available page header; and preventing any resource information from appearing on the first page header (and desirably not even analysing the first page for resource information) each have their advantages, as later discussion indicates. The invention further provides printers, computers, computer systems, and software adapted to provide elements necessary to performance of the methods indicated above. Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows schematically the processing of information for printing of a document by a printer from a computer in a conventional arrangement; Figure 2 illustrates a typical arrangement of computer and printer to which the present invention is applicable; Figure 3 shows schematically the processing of information for printing of a document by a printer according to embodiments of the present invention. Figure 2 shows a typical arrangement for printing from a computer. Personal computer 8 has a processor 13 and a memory 12 (in both cases there may be a number of components involved - the "processor" may include a main microprocessor and coprocessors, for example, and there may be several different forms of memory). Communication is established with a printer 9 through a network connection 11. The printer 9 also has a processor 14 for control of the printer and a memory 15 for use by the processor. Embodiments of the present invention can be employed for use with the arrangement shown in Figure 2 - the skilled man will readily understand that the present invention can also be employed in other embodiments to other forms of connection between a computer and a printer using the principles set out herein. Embodiments of a printing process according to the present invention are now described with reference to Figure 3. The initial stage of the process is (typically) as shown in Figure 1: an application 1 generates a printer independent form 5 of a document (one or more pages) to be printed. This printer independent form of the document is passed to the printer driver 2. At this point, there is a difference from the conventional printing process. The printer driver constructs PDL and JCL to pass to the printer 9, but also while constructing the PDL identifies information that would affect how the printer 9 allocates its resources, and writes this information to a table 31. This is not a particularly onerous task, as particular PDL and JCL instructions produced by the printer driver 5 in conventional languages can be identified in advance as having such resource implications - however, in conventional languages such instructions are merely embedded into the stream at the point at which their significance arises in the document, allowing no possibility of advance management of printer resources. Information that affects resources in such a way would include use of a new font (its type, size, and required characters) or of bitmapped graphics (dimensions, depth, colour scheme, file type, manipulations). The printer specific page description 6 produced by the printer driver 2 does not contain any of the resource information provided in table 31 except as PDL or JCL instructions embedded within the page description in the conventional way. Resource annotation stage 32 provides a mechanism for adding this resource information into the page description in a way that will allow the printer 9 to allocate resources effectively. An effective mechanism is to provide the resource information held in table 31 as comments (such comments are hereafter referred to as "resource declaration") in page headers of the PDL pages. The comments may relate to the page on which they are provided as headers, or, more advantageously, may relate to later pages, in which the printer processor has more time to allocate its resources. Different strategies can be used according to the desired objective. The following approaches will be advantageous in different situations. (i) Resource declarations for the whole document are provided on the first page of the document. This provides the maximum assistance to the printer 9 in allocating its resources, as a full timetable can be constructed before commencement of the job. Disadvantages are that the job cannot be sent to the printer until all the resource declarations have been added, and that the first page of the document may print slowly (though subsequent pages will be provided with a minimum likelihood of stalls). (ii) Resource declarations are provided incrementally. In this case, pages are passed to the printer as soon as this is possible, with resource declarations added to the header of the first available page. Provided the analysis to achieve page declarations is sufficiently rapid, this should generally be of comparable effectiveness to method (i) (though the risk of stalls would be at least marginally greater) and printing would commence, and probably finish, more quickly. (iii) As either method (i) or method (ii), but adapted such that either no resource declarations are provided on the first page of the document or the first page of the document is not analysed for resource declarations or (preferably) both. This maximises the speed of printing the first page of the document (an important metric for evaluation of printers), although it may increase the risk of a stall if the first or second page of the document is particularly complex. Essentially, the resource information is provided as a separate logical channel to the print data (provided by the conventional PDL without annotations), and use of resource declarations is simply a mechanism to allow effective combination of these two logical channels on to a single transport link 7 for communication to the printer 9. Methods (i) to (iii) above merely form alternative types of this basic mechanism. Table 1 shows for one Postscript example resource information determined by print driver 2 and written to table 31 (in this case, font information), together with the main features of the PDL itself. Resource Channel Data Channel page1:cmr@10,3; %!PSAdobe-3.0 pagel :cmi@10.4; %%pages:N page2:cmi@10.1; %%EndComments page3:cmr@10.3; %%Page1 page4:cmr@10.34 ... ... %%Page2 pageN:cmr@11.3 ... %%Page3 ... ... %%PageN When integrated into commented PDL by the resource annotation stage, the result could be as shown in any of the three columns in Table 2, depending on the method employed. Initial Declarations (Method i) Incremental Declarations (Method ii) Fast Page One (Method iii, here as modification to Method ii) %!PSAdobe-3.0 %!PSAdobe-3.0 %!PSAdobe-3.0 %%pages:N %%pages:N %%pages:N %BeginResourceDeclarations %BeginResourceDeclarations %%Page1 %Resource page1:cmr@10.3; %Resource page1:cmr@10.3; ... %Resource page1:cmi@10.4; %Resource page1:cmi@10.4; ... %Resource page2:cmi@10.1; %Resource page2:cmi@10.1; ... %Resource page3:cmr@10.3; %EndResourceDeclarations %Resource page4:cmr@10.34; %%EndComments %Resource ... %%Page1 %Resource pageN:cmr@11.3 ... %EndResourceDeclarations ... %%EndComments ... %%Page1 ... ... ... %%Page2 %%Page2 %%Page2 ... %BeginResourceDeclarations %BeginResourceDeclarations ... %Resource page3:cmr@10.3; %Resource page2:cmi@10.1; %EndResourceDeclarations %Resource page3:cmr@10.3; ... %EndResourceDeclarations ... ... ... %%Page3 %%Page3 %%Page3 ... %BeginResourceDeclarations %BeginResourceDeclarations ... %Resource page4:cmr@10.34; %Resource page4:cmr@10.34; %Resource ... %Resource ... %Resource pageN:cmr@11.3 %Resource pageN.-cmr@11.3 %EndResourceDeclarations %EndResourceDeclarations ... ... ... ... %%PageN %%PageN %%PageN ... ... ... ... ... ... The resource annotation stage 32 may be a part of the printer driver itself. Other possible locations in the pipeline are possible, and table 31 can be compiled by components other than the printer driver. The resource table 31 could for example be compiled by the application 1 (in the case of certain applications which generate the PDL directly) or by the print spooler 3, or by some resource filter sitting between the application 1 and the printer driver 2, the printer driver 2 and the print spooler 3, or the print spooler 3 and the printer 9. The resource annotation stage obviously cannot be any earlier in the pipeline than the point at which the resource table 31 is compiled, but it can sit either in the same component or at a later stage. In the Figure 3 example, the resource annotated page description 33 is sent to the print spooler 3 and then out on to the transport connection 7 to the printer 9. The resource annotated page description is received by the printer processor 4, which is adapted to recognise which of the comments in the annotated PDL are resource declarations. The resource declarations are extracted, and processing of the appropriate tasks is scheduled so that when the page to which they relate is to be printed, sufficient of the task will be completed to prevent the possibility of a stall. Although the difference to the printer processor is significant in practice, significant redesign is not required. The tasks for which resources are to be allocated are not different from those required normally - the difference is only that advance notice is given, allowing the printer processor 4 to schedule tasks earlier, and more conveniently, than is possible with conventional printing approaches An advantage of using commented Postscript (or comments in any other language recognised by the printer) is that if the printer is not enabled to handle resource allocation according to the present invention, the print job can still be processed in the normal way - the substance of the PDL as seen by the printer is unaffected and the comments are (like other comments) simply ignored. Embodiments of the invention can thus be provided to ensure backward compatibility with existing printers. In the embodiments described above, the two logical channels - resource channel and data channel - are combined into one unified channel of annotated data. With a printer structure adapted appropriately, these two logical channels could be kept entirely separate - the data channel provided directly to the printer in the conventional way, and the resource channel provided separately (possibly on the same physical wire, but as a different stream of packets) and received and interpreted by a specifically adapted part of the printer - possibly a separate processor in the printer, or possibly as a separate activity within the existing printer processor.

Claims: A method of printing a document from a computer (8) with a printer (9), the printer (9) having a printer processor (14), the method comprising: generating in the computer (8) instruction data to enable the printer (9) to print the document; generating in the computer (8) resource information indicative of printer processor resources required by the printer (9) at different stages of printing the document; sending the instruction data and the resource information from the computer (8) to the printer (9), scheduling printer processor resources for the different stages of printing the document in accordance with the resource information; and printing the document with the printer processor resources as scheduled. A method as claimed in claim 1, wherein the instruction data is provided as page description language and/or job control language. A method as claimed in claim 2, wherein the resource information is provided as annotation to the page description language and/or job control language, and wherein the method comprises after the step of generating resource information the step of annotating the instruction data with the resource information. A method as claimed in claim 3, wherein a common information processing structure carries out the steps of generating the instruction data, generating the resource information, and annotating the instruction data with the resource information. A method as claimed in claim 4, wherein the common information processing structure is a printer driver. A method as claimed in claim 3, wherein a first information processing structure carries out the step of generating the instruction data, and a second information processing structure carries out the steps of generating the resource information and annotating the instruction data with the resource information. A method as claimed in claim 6, wherein said second information structure is located in an information path for instruction data from the first information processing structure to the printer. A method as claimed in claim 7, wherein said second information structure is a print spooler. A method as claimed in claim 7, wherein said second information structure is a discrete structure receiving the instruction data as input and providing instruction data annotated with the resource information as output. A method as claimed in any of claims 3 to 9, wherein the annotation is provided in the form of comments in the page description language and/or job control language, and wherein the method comprises between the steps of sending the instruction data and the resource information from the computer to the printer and scheduling printer processor resources a further step of filtering the comments in the page description language and/or job control language to extract the resource information. A method as claimed in claim 10, wherein the resource information is provided as comments in page headers of the page description language. A method as claimed in claim 11, wherein the resource information is provided as comments in the page header to the first page of the document. A method as claimed in claim 11, wherein the resource information is provided incrementally in a plurality of page headers. A method as claimed in claim 13, wherein page headers contain resource information for the page to which they relate or to later pages in the document if such resource information has not already been provided in previous page headers. A method as claimed in claim 11, 13 or 14, where no resource information is provided as a comment to the page header of the first page. A method as claimed in claim 15, wherein the step of generating resource information does not include generation of resource information for the first page of the document. A printer (9) adapted to print a document from instruction data and resource information, the printer (9) having a printer processor (14), such that the printer processor (14) is adapted to schedule its resources for the different stages of printing the document from the instruction data in accordance with the resource information, and to print the document from the instruction data with the printer processor resources as scheduled. A printer as claimed in claim 17, wherein the instruction data is provided as page description language and/or job control language. A printer as claimed in claim 18, wherein the resource information is provided as annotation to the page description language and/or job control language. A printer as claimed in claim 19, wherein the annotation is provided in the form of comments in the page description language and/or job control language, and wherein the printer processor is adapted to filter the comments in the page description language and/or job control language to extract the resource information. A computer (8) programmed to provide a document for printing by a printer (9), the programmed computer (8) having: a first information processing structure to generate instruction data to enable a printer (9) to print the document; a second information processing structure resource to generate resource information indicative of printer processor resources required by the printer (9) at different stages of printing the document; and an information path (7) such that the instruction data and the resource information can be sent from the computer (8) to a printer (9). A computer as claimed in claim 21, wherein the first information processing structure generates instruction data as page description language and/or job control language. A computer as claimed in claim 22, wherein the second information processing structure generates resource information as annotation to the page description language and/or job control language, and is adapted to annotate the instruction data with the resource information. A computer as claimed in claim 23, wherein the first information processing structure and the second information processing structure are combined in a common information processing structure. A computer as claimed in claim 24, wherein the common information processing structure is a printer driver. A computer as claimed in claim 23, wherein said second information structure is located in the information path between the first information processing structure and a printer. A computer as claimed in claim 26, wherein said second information structure is a print spooler. A computer as claimed in claim 26, wherein said second information structure is a discrete structure receiving the instruction data as input and providing instruction data annotated with the resource information as output. A computer as claimed in any of claims 23 to 28, wherein the second information structure is adapted such that the annotation is provided in the form of comments in the page description language and/or job control language. A computer as claimed in claim 29, wherein the second information structure is adapted such that the resource information is provided as comments in page headers of the page description language. A computer as claimed in claim 30, wherein the second information structure is adapted such that the resource information is provided as comments in the page header to the first page of the document. A computer as claimed in claim 30, wherein the second information structure is adapted such that the resource information is provided incrementally in a plurality of page headers. A computer as claimed in claim 30 or claim 32, where the second information structure is adapted such that no resource information is provided as a comment to the page header of the first page. A computer as claimed in claim 33, wherein the second information structure is adapted so as not to generate resource information for the first page of the document. A computer system comprising a printer (9) as claimed in any of claims 17 to 20, a computer (8) as claimed in any of claims 21 to 34, and a communication path (7) adapted to carry information from the computer (8) to the printer (9). An article of manufacture comprising a program storage medium having computer readable program code means embodied therein for causing a document to be provided in an enhanced form for printing by a printer (9), the computer readable program code means in said article of manufacture including: computer readable program code means for causing a computer (8) to generate instruction data to enable a printer (9) to print the document, wherein the instruction data is provided as page description language and/or job control language; and computer readable program code means for causing the computer (8) to generate resource information indicative of printer processor resources required by the printer (9) at different stages of printing the document, and to annotate the instruction data with the resource information, thereby providing the annotated instruction data for printing by the printer (9). An article of manufacture comprising a program storage medium having computer readable program code means embodied therein for enhancing information enabling a document to be provided for printing by a printer (9) to improve printer performance, said information being provided as instruction data in the form of page description language and/or job control language, the computer readable program code means in said article of manufacture comprising computer readable program code means for causing a computer (8) to generate resource information indicative of printer processor resources required by the printer (9) at different stages of printing the document, and to annotate the instruction data with the resource information, thereby providing the annotated instruction data for printing by the printer (9).

Inventors: BEN-ISMAIL TAREK, BROWN JASON JAMES, RAHMOUNI MAHER, TAYLOR RICHARD, BEN-ISMAIL, TAREK, BROWN, JASON JAMES, RAHMOUNI, MAHER, TAYLOR, RICHARD
Applicants: HEWLETT PACKARD CO, HEWLETT-PACKARD COMPANY
Application year: 1999
Main classification: G06F3
IPC codes: G06F3