WO2001050236A1 - Dispositif et procede d'impression - Google Patents

Dispositif et procede d'impression Download PDF

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Publication number
WO2001050236A1
WO2001050236A1 PCT/SE2000/000002 SE0000002W WO0150236A1 WO 2001050236 A1 WO2001050236 A1 WO 2001050236A1 SE 0000002 W SE0000002 W SE 0000002W WO 0150236 A1 WO0150236 A1 WO 0150236A1
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WIPO (PCT)
Prior art keywords
halftone
data
array
pixel
sample
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PCT/SE2000/000002
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English (en)
Inventor
Sven Stefan Blixt
Tomas Jonsson
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Array Ab Publ.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Array Ab Publ. filed Critical Array Ab Publ.
Priority to AU29518/00A priority Critical patent/AU2951800A/en
Priority to PCT/SE2000/000002 priority patent/WO2001050236A1/fr
Publication of WO2001050236A1 publication Critical patent/WO2001050236A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/405—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels
    • H04N1/4051—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels producing a dispersed dots halftone pattern, the dots having substantially the same size
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/405—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels
    • H04N1/4055—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels producing a clustered dots or a size modulated halftone pattern

Definitions

  • the present invention relates to data processing in printing equipment in general and in particular to halftoning of high-resolution images.
  • a processing unit typically provides an image in the form of a pixel array. Each pixel is associated with a certain intensity level. For a colour image, one pixel array for each elementary colour is provided.
  • a printer operates typically by positioning dots of different colours over the printing area. In a typical case, the printer dots are all of one and the same intensity.
  • the distribution of the dots are used for create an impression of general intensity levels.
  • the procedure of determining such a distribution of dots is generally known as halftoning.
  • the general object of the halftoning is to provide a dot distribution, which gives a true impression of the local intensity level.
  • the most common way of performing such a dot distribution is to use a halftone cell, consisting of an array of pixels.
  • the pixels in the halftone cell are lit one after another, to correspond to an increased intensity level. That means, that a certain intensity level corresponds to a halftone cell with a certain number of lit pixels arranged in a certain fashion. For a higher intensity, more pixels are lit.
  • the typical manner to perform this is to let a pixel that is lit at a certain intensity level be lit at all higher intensity levels. That means, that for each pixel in the halftone cell, there exists a certain intensity threshold, over which the particular pixel is lit.
  • the halftone cell array When performing halftoning, the halftone cell array is placed all over the image area, covering all pixels of the original image. For each pixel, where the intensity level of the original image is larger than the threshold of the corresponding pixel in the halftone cell, the pixel is lit.
  • One example of a distribution structure is given in the American patent US 5,957,593.
  • a processing unit provides a pixel array of pixels having an intensity level associated with them.
  • a comparison is made for each pixel, if the actual intensity level in the pixel exceeds the threshold value of the corresponding pixel of the halftone cell.
  • Such a procedure is typically performed in software, including the algorithms for calculating the thresholds.
  • Simple microprocessors of today have the processing power to perform such comparisons for medium resolution images in fairly reasonable times.
  • Halftoning processes and equipment according to the prior art thus have the common problem of too long processing times. Furthermore, the software processes according to the prior art also restricts the type of dot distribution algorithms that can be used.
  • An object of the present invention is thus to provide methods and devices for halftoning, which allows a higher printing speed.
  • a further object of the present invention is also to provide halftoning methods and devices which are capable of using a larger variety of dot distribution algorithms.
  • Another object of the present invention is to provide an efficient resolution enhancement during the halftoning process.
  • a set of predetermined halftone samples is created. Each one of the samples corresponds to a certain intensity level.
  • each elementary colour has its own set of halftone samples.
  • the halftone sample sets are stored, preferably as a look-up table, in a memory unit. Each pixel in these samples is associated with an output intensity level, which in the typical case is restricted to one out of two levels, on or off.
  • a first array of pixel data is provided as input image data. The input data is scanned pixel by pixel, and the intensity level of each pixel is read.
  • the predetermined halftone samples in the memory are accessed, using the line and column position together with the intensity level as an address, pointing at a certain pixel in one of the halftone samples.
  • the intensity value of that pixel is read and output as a pixel at a second array of data, to be sent to the printer.
  • the memory access is performed by only using logic hardware elements, thus increasing the processing speed. In the case of colour images, the colour also acts as a part of the access address.
  • the logic hardware elements are implemented as an application specific integrated circuit or in a field programmable gate array.
  • the memory is preferably a flash memory, which also may contain configuration data for the field programmable gate array.
  • any dot distribution algorithms may be used, which is based on the colour, intensity level, and line and column position. Combinations of amplitude modulated halftoning and frequency modulated halftoning is easily achievable, as well as samples, where the lightening of pixels at one intensity level do not necessarily influence the situation at a higher intensity level. Intensity linearity compensation is also achievable, by modifying the number of lit pixels corresponding to a certain intensity level.
  • the method is also easily adaptable for printers, printing dots of different intensity levels, whereby also the intensity levels can be used for achieving an enhanced intensity linearity.
  • FIG. 1 is an illustration of a halftone cell with intensity threshold indications used in the prior art
  • FIG. 2a is an illustration of a number of predetermined halftone samples, which can be used in the present invention.
  • FIG. 2b is an illustration of a set of halftone samples according to the present invention.
  • FIG. 3 is a block diagram illustrating the general features of a printer controller according to the present invention.
  • FIG. 4 is a block diagram of an embodiment of a printer controller according to the present invention.
  • FIG. 5 is a diagram illustrating the data transfer to a printer according to the embodiment of fig. 4;
  • FIG. 6a is a schematic drawing of the procedure of accessing predetermined halftone samples according to the present invention.
  • FIG. 6b is an illustration of a halftoned image with a uniform intensity
  • FIG. 7 is a schematic drawing of the procedure of accessing predetermined halftone samples in a resolution enhancement procedure according to the present invention.
  • FIG. 8a-8e are examples of halftone samples useful in the present invention.
  • FIG. 9a and 9b are diagrams illustrating intensity inlinearities and linearity compensation
  • FIG. 10a is a flow diagram of a general halftoning method according to the present invention.
  • FIG. 10b is a flow diagram illustrated a preferred access of halftone samples according to the present invention.
  • FIG. 11a -l ie illustrates examples of halftone samples presenting more than two intensity levels.
  • the halftoning process involves the transformation of an intensity scale to a geometrical pattern of dots.
  • a schematic illustration of threshold intensity values of a halftone cell is shown, represented as a pixel 10 and arranged in a number of rows 12 and columns 14. Only one of each type of item is provided with reference numbers, for improving the readability of the figure.
  • An incoming pixel with a certain position of row 12 and column 14 is assigned to a corresponding one of the threshold values.
  • the intensity value of the incoming pixel is then compared with the threshold intensity value for that particular pixel 10. If the incoming pixel intensity value exceeds the threshold value, an outgoing pixel is set to be lit, i.e. a dot is going to be printed in the corresponding position. If the incoming pixel intensity value is lower than the threshold, there will be no dot printed.
  • software processors take care of this comparison procedure for each incoming pixel.
  • a certain pattern will be created and copied all over the surface.
  • a number of halftone samples 16 corresponding to such patterns are illustrated in fig. 2a, for the set of thresholds of the halftone cell of fig. 1. For an intensity level of zero, no dots are to be printed. For an intensity level of " 1", one dot is printed, and so on. The entire sample 16 is then filled at intensity level 25.
  • Such a group of predetermined halftone samples is easily produced, where each sample corresponds to a particular intensity level. They may be stored together as a set 18 of predetermined halftone samples, as illustrated in fig. 2b. In this three-dimensional data arrangement, the intensity level 20 is determined by the vertical position.
  • a certain intensity level 20 determines which sheet or sample is to be used, while the row 12 and column 14 determines the pixel 10 in a conventional manner. The content in the pixel 10 then immediately indicates whether a dot is to be printed or not, without any need for calculations.
  • a halftoning unit is comprised in the printing system at some stage.
  • the halftoning unit can be a separate unit, or comprised in either the processing unit delivering the images to be printed or in the printer itself.
  • a processing unit 30 creates or processes an image, forming an array of pixels 34, in which each pixel is associated with a certain intensity level.
  • the array of pixels 34 is sent to a halftoning unit 40, which performs a halftoning procedure on the pixel array 34 and produces an outgoing array of pixels 36, ready for printing.
  • each pixel is typically only indicating the occurrence of a dot or not.
  • a general outgoing intensity level may be associated with each pixel also in the outgoing array of pixels 36.
  • a pixel in the outgoing array of pixels 36 will only indicate one out of two possibilities; printing a dot or not, i.e. the intensity levels of the halftone samples are selected as either of two values.
  • the outgoing array of pixels 36 is subsequently sent to a printer 32 for executing the actual printing.
  • the halftoning unit 40 may be an integrated part of the processing unit 30 or an integrated part of the printer unit 32, but may also be presented as a separate unit.
  • the halftoning unit 40 according to the present invention comprises a hardware logic section 42, which is responsible for extracting the halftoning data, and a memory unit 44, comprising at least one set of predetermined halftone samples 18.
  • the hardware logic section 42 is arranged to use pixel coordinates and the intensity value associated with the pixels of the incoming pixel array 34 to address the memory unit 44.
  • the halftone samples 18 in the memory unit 44 comprises the information about whether a dot is to be printed or not, without any need for any comparison or calculation.
  • predetermined halftone data comprises at least one set of halftone samples, where each halftone sample corresponds to a certain first intensity level and where each pixel in the halftone samples is associated with a certain sample intensity.
  • the intensity levels of the outgoing pixel array are thus based on the sample intensity levels.
  • the hardware logic unit 42 can be implemented as an application specific integrated circuit (ASIC), tailored to suit the particular application and device. The ASIC may then be very simple and thereby very fast and cheap, even at rather small manufacturing series.
  • the hardware logic unit 42 may also preferably be implemented as a field programmable gate array (FPGA). This opens the possibility to change the behaviour of the hardware logics according to alternative or updated procedures.
  • the halftoning unit 40 also comprises means 48 for configuring the FPGA hardware logics. Configuration data for the field programmable gate array is also stored in a memory 46, preferably the same as being used to store the predetermined halftone samples 18. By using FPGA techniques, a number of different halftoning procedures may be implemented in a simple manner in one and the same unit.
  • the appropriate halftoning procedure is selected, the configuration data from the memory unit 44 is used to configure the hardware logic unit 42, and the halftoning unit is ready for use. Once the hardware structure is determined, the actual halftoning procedure takes place, using exclusively hardware components for its operation.
  • a colour image may comprise up to four sets of pixel arrays, three ones corresponding to a certain respective elementary colour, and sometimes a fourth one for printing black. Each pixel in each set then corresponds to an intensity level for the particular colour.
  • the memory unit 44 comprises one set of predetermined halftone samples per colour. The halftoning unit 40 then incorporates a logical function to determine which one of these sets to be used.
  • a processing unit interface 50 uses connections 54, 56, 58, 60 for signals DATAREQ, DATA, WR_DATA and WR_COL.
  • DATAREQ 60 is activated every time the halftoning unit 40 needs more data from the processing unit, i.e. it trigs the incoming pixel data.
  • the connection for DATA is a data bus 54 that transfers data from the processing unit to the halftoning unit 40. This data generally incorporates both video data and colour information.
  • the signal WR_DATA 56 is used for video data load during printing, and WR_COL 58 is used to set up the halftoning map according to the colour selection.
  • the image data is put into a data FIFO (First In First Out) memory unit 74.
  • the image data comprises 8 bits, which corresponds to 256 intensity levels.
  • the image data is stored temporarily in the FIFO, waiting for processing.
  • the colour data is put into a colour latch 76, holding 2 bits, which is enough to define one of the three elementary colours.
  • a control logic block 80 is the heart of the halftoning unit 40. The control logic block 80 sends the DATAREQ signal to the processing unit when data is requested. It also controls the reading of the predetermined halftone samples, stored in the flash memory 44.
  • a column counter 70 is provided to keep track of the horizontal position associated with the image data and a line counter 72 is provided to keep track on the vertical position.
  • Two connections are provided between the control logic block 80 and the column counter 70, in order to provide control signals for reset 82 and incrementing 84 of the column counter 70.
  • two connections are provided between the control logic block 80 and the line counter 72, in order to provide control signals for reset 86 and incrementing 88 of the line counter 72.
  • the column counter 70, the line counter 72, the data FIFO 74 and the colour latch 76 are arranged to access the flash memory 44 of a certain address, controlled by the control logic unit 80.
  • the content in the memory position of the particular address is supplied to a video latch 78. This content may be of different length, depending on the particular application.
  • the read-out value consists of only one bit, where 1 indicates a dot and 0 the absence of a dot.
  • the video latch 78 data is stored until an appropriate read-out to the printer may be performed.
  • a printer interface 52 has four connections 62, 64, 66, 68 to the printer.
  • a data path 62 is provided to the printer for transmitting the outgoing video data.
  • the data path 62 can use any width, from 1 bit for pure serial data to n bits for semi-serial data.
  • the control logic block 80 controls the read out of video data to the printer.
  • a video clock signal VCLK 64 is provided to the control logic block 80, controlling the reading out of video data from the video latch 78.
  • a signal VSYNC 68 is activated when a paper (or transfer belt/OPC drum) reaches the start of print position. It is deactivated when a page print is done.
  • a signal HSYNC 66 is activated when a line print is started, and deactivated when the line print is ready.
  • NSYNC will be activated once during each page, and HSYNC is activated once for every line on the page. Data transfer from the halftoning unit 40 to the printer should take place synchronously to the VCLK signal 64 when both HSYNC and VSYNC are active.
  • Fig. 5 is a diagram illustrating the data transfer to a printer according to the embodiment of fig. 4.
  • the three top curves illustrate the signals VCLK, VSYNC and HSYNC, respectively.
  • the clock signal has a rising edge and a falling edge. A data transfer is taking place at each rising edge if both the VSYNC and HSYNC signals are high.
  • the VSYNC signal is activated at to, when the paper has reached the print position.
  • the HSYNC becomes high, which indicates that a first line on the page may be printed, since both HSYNC and VSYNC are high.
  • the first subsequent rising edge of the VCLK appears, and data is read out to the printer.
  • next read out takes place and so on until t4 and ts.
  • the first line is at its end and the HSYNC signal goes low, which prohibits any further data transfer.
  • the second line on the page is ready to be written and the HSYNC becomes high, which enables writings at ts and t9 and so on.
  • the general operation thus follows the following process.
  • predetermined halftone sample sets are stored for each colour.
  • the data consists of samples for every possible intensity level.
  • both the line and column counters are reset and the colour selection is made.
  • the colour value selects the set of halftone samples that is going to be used.
  • Image data is entered via the data bus 54.
  • the image data from the processing unit is interpreted as a sample number within the set of halftone samples and selects one of the samples, corresponding to the particular magnitude of the image intensity.
  • the column counter 70 and the line counter 72 defines the column and row, respectively, from which the output data should be fetched.
  • the first value is thus fetched from the position [0,0] at the sample corresponding to the intensity value of the first data (in the selected colour set). This value is sent to the video latch 78.
  • the column counter is incremented one step by the connection 84 and the next data is fetched from the flash memory 44 to the video latch 78. In this case it corresponds to the cell [1,0] of the sample corresponding to the intensity value of the second data provided from the processing unit.
  • the column counter 70 is incremented until it reaches N, the number or columns in a predetermined halftone sample. In such a case, the column counter starts all over again from zero.
  • the printer When the printer reaches the end of the line, it will continue on the next line.
  • the line counter 72 is thus incremented, while the column counter 70 is reset to zero.
  • the first data fetch will now be made from cell [1,0] at the halftone sample decided by the intensity value input from the processing unit via the data FIFO 74.
  • the next data will be fetched from cell [1, 1] and so on.
  • the line counter When the number of lines has reached M, the number of lines of the halftone samples, the line counter will be reset and started all over again.
  • FIG. 6a the fetching process is illustrated in a more schematic manner.
  • An incoming data array of K columns and L lines is entering into the halftoning procedure.
  • the resolution is in this case 150 dpi (dots per inch).
  • a set of I predetermined halftone samples 18 with N columns and M rows are available in the halftoning unit.
  • an intensity value of io is present in the pixel [ko,lo] in the incoming data. This value io determines the actual sample, from which the outgoing data is going to be fetched.
  • a cell [no,mo] in the predetermined halftone sample of level io is fetched.
  • the values of no and mo are selected as the rest part of the integer division of ko/n and lo/M, respectively. This is easily performed by the counter operation described above.
  • the value of the cell [no,mo] is outputted as pixel data for the printer 36. In this particular case, the data was a " 1", which means that a dot will be printed in the corresponding position.
  • the outgoing resolution is still 150 dpi.
  • fig. 6b an illustration of a halftoned image with a certain uniform intensity is shown. Here, the distribution of the halftone samples covering the entire image surface is clearly seen.
  • the present invention may improve the speed of the halftoning.
  • the advantages become even larger in systems where a resolution improving halftoning procedure is used.
  • a resolution enhancement by a certain factor will increase the computational time with the same factor. It is an advantage to use a resolution of the outgoing pixel array of at least 300 dpi, at more preferably at least 600 dpi. The situation in a device according to the present invention will be different, as described here below.
  • a resolution enhancing halftoning procedure is described, i.e. the resolution of the outgoing pixel array is higher than the resolution of the incoming pixel array.
  • the incoming data corresponds to a resolution of 150 dpi both in horizontal and vertical direction. However, the outgoing data has a vertical resolution of 600 dpi and a horizontal resolution of 300 dpi. If the incoming data has K columns and L lines, the outgoing data thus has 4K columns and 2L lines. In a conventional halftoning process, this would give rise to a treatment time 8 times longer than for a normal 1-to-l halftoning. In the present example, the present invention will have about the same processing time.
  • a pixel [k ⁇ ,l ⁇ ] with an intensity value of ii now corresponds to an array of data on halftone sample No. ii.
  • the pixel corresponds to an array with four columns and two rows. Instead of reading out one single value to the outgoing data, the whole array of 8 values is read and outputted.
  • the time for reading the array will be in the same order of magnitude as reading a single value, which means that the processing time is not very much higher than for a halftoning process without resolution enhancement.
  • the array of the halftone sample that is simultaneously read out has a number of columns, which is equal to the ratio between the horizontal resolutions of the outgoing and incoming data, respectively, and has a number of rows, which is equal to the ratio between the vertical resolutions of the outgoing and incoming data, respectively. It is thus preferable, if these ratios are integers. It is also easily understood that it is an advantage to have halftone samples with a number of columns and rows, which are a pure multiple of the respective ratios.
  • the outgoing data is normally outputted one row after another. If a vertical resolution enhancement takes place, more than one row may be read out from the halftone sample at each memory access. In such a case, the multi-row information read out from the halftone sample may be stored in the video latch 78, and read out to the printer, row by row.
  • An alternative way is to repeat reading a certain row of the incoming data a number of times, corresponding to the vertical enhancement, and each time only read one row of the array from the halftone sample. However, this means that the processing time will increase correspondingly.
  • a halftone sample is shown, illustrating an amplitude modulated halftoning.
  • the size of the composite spots is variable while their spacing is constant.
  • the spot grows larger as the intensity increases.
  • the distance from the centre of one composite spot to the next is always the same. In other words, this means that the diameter of the composite spot increases, with an increased intensity.
  • a halftone sample is shown, illustrating a frequency modulated halftoning.
  • the size of the elementary dots is kept constant, while their spacing varies.
  • the number of dots within the halftone sample increases as the intensity value becomes darker. In other words, this means that dots of a certain minimum size is placed out over the halftone sample area one after another, as evenly spread as possible.
  • the size of the real dots on the paper is normally much larger than the theoretical size according to the printing "resolution”. This means that two elementary dots, being placed in adjacent positions at the halftone samples, do not increase the apparent intensity to the twice of one single dot. Also, if the resolution is high enough, the eye can not separate two dots from each other, even if they are separated by several "empty" positions.
  • the halftone samples for a low intensity follows the rules according to the frequency modulated method.
  • the mean distance between individual spots in a halftone sample reaches the resolution limit of the eye, around 150 dpi, an increased number of spots will not fill in any "empty" spaces, but will only serve to make the "intensity scale" somewhat more in-linear, as further discussed below.
  • Such a situation is illustrated by the sample in fig. 8c, with a mean distance d between the dots.
  • the intensity scale may be improved. This means that the number of spots is not increased any more, but instead the size of the composed spots are increased.
  • a halftone sample of a higher intensity value is shown in fig. 8d.
  • the mean distance is still d, while the size of the composite spots is larger.
  • the halftone samples are frequency modulated halftone samples- below a certain predetermined halftone sample resolution, and amplitude modulated halftone samples above the same resolution.
  • a limitation of using threshold based models according to the prior art is that the type of algorithms used is limited. Assume that a certain intensity level corresponds to the frequency modulated sample of fig. 8b. When creating a suitable halftone sample for the double intensity level, keeping the lit cells still lit introduces severe limitations. A good choice for a halftone sample would be the one presented in fig. 8e. However, every second of the cells lit in fig. 8b is out in fig. 8e. Instead, three other cells are lit. Such a halftoning is not possible to perform in a simple manner by a software based system, at least not if it is based on threshold arguments. With the present invention, the relation between a halftone sample for a certain intensity level and the samples for higher intensity levels is not fixed.
  • a cell that is lit at one level may be out in the next, and so on.
  • at least one pair of halftone samples, corresponding to consecutive intensity levels are independent of each other. That means that at least one pixel in the halftone sample corresponding to the higher intensity level has a lower sample intensity level than the corresponding pixel in the halftone sample corresponding to the lower intensity level. In the case of only two sample intensity levels, this means that at least one lit pixel in a lower intensity halftone sample is out in a higher intensity halftone sample.
  • the number of lit pixels between two adjacent intensity level samples may differ by more than one. This gives the possibility to compensate for inlinearities in the intensity scale. At low intensities, where each dot gives rise to a high intensity increase, the number of additional lit pixels for each sample level may be kept lower than an average value. In the contrary, the number of additionally lit pixels between sample levels at the high intensity end, is made larger.
  • fig. 9b a relation between the number of lit pixels, i.e. the number of printed dots, and the actual intensity level is illustrated. An uncompensated relation will follow the broken line 96, while a compensated relation may look like the curve 98.
  • step 102 a first array of pixel data is input.
  • step 104 a halftoning procedure is provided onto this first array of pixel data, creating a second array of pixel data.
  • the halftoning procedure is performed by using predetermined halftone data accessed by hardware logics.
  • the halftone data comprises preferably a multitude of halftone samples, each one corresponding to a certain intensity value.
  • step 128, the second array of pixel data is output for printing and the procedure stops at step 130.
  • step 104 of fig. 10a is presented in more detail.
  • the first array of pixel data is assumed to be available as a series of intensity values by step 102 of fig. 10a.
  • a line counter is reset and in step 108 a column counter is reset.
  • An intensity value corresponding to the first pixel of the first array of pixel data is read in " step 110 and a table value corresponding to the line counter, column counter and intensity value is found in step 112 and read out in step 114.
  • the column counter is incremented one step in step 116.
  • step 118 it is decided whether or not the end of the image line is reached, i.e. if the first row of pixels in the first array of pixel data is treated.
  • step 120 it is decided whether or not the column counter has reached the number of columns in the predetermined halftone samples. If that is not the case, the process goes back to step 110, for reading a new intensity value. If the column counter has reached the end of a line at the halftone sample, the process instead returns to step 108 for resetting the column counter.
  • step 122 when an image line is completed, the line counter is incremented one step.
  • step 124 it is decided whether or not the end of the image page is reached. If this is true, the process continues to step 128 for outputting the second array of data. If the image page end is not reached in step 124, the process continues with step 126, where it is decided if the line counter has reached the number of lines in the halftone samples. If there are lines left in the halftone sample, the process returns to step 108, starting treating a new line. If the last line of the halftone sample is treated, the process instead returns to step 106 for resetting the line counter, starting with a new copy of the halftone sample set.
  • the printers of today have the possibility of an inherent dot intensity regulation. This may be accomplished either by varying the actual spot size, or reducing the amount of print ink used for the spot. In such cases, a limited intensity modulation can be performed directly by the printer, and the sample intensity levels are then selected from a set of at least three values.
  • the present invention is suitable also for serving these purposes.
  • the halftone samples may in such a system be formed as array of pixels, where each pixel is associated with a coarse intensity level. If the printer for example has the possibility to print dots with four different intensities, the halftone sample pixels may have an intensity level of between 0 and 4. The dynamics of the system will thereby increase, since there are more parameters to be varied in order to optimise the halftoning algorithms.
  • fig. 11a Some examples are shown in fig. 11a to l ie.
  • fig. 11a a low intensity sample is illustrated, where only four pixels have non-zero values, and each one of these only indicates the lowest dot intensity.
  • fig. l ib a high intensity sample is illustrated, where all pixels have non-zero intensity values, and most of them the second highest one.
  • the second or outgoing array of pixels will in these cases have an intensity resolution of 4 steps instead of just one.
  • Such a printer intensity modulation may advantageously be used for adjusting for inlinearities in intensity. Since the edges of sample spots are the most sensitive areas concerning such inlinearities, a reduced intensity value in the edges of spots and a higher intensity in the interior of such spots will decrease intensity inlinearities.
  • Fig. l ie illustrates an example where a spot has a high intensity interior, indicated by the intensity level 4, and low intensity edges, with an intensity level of 1. At the high intensity end, the corresponding treatment will lead to the result that the last added pixels will have a larger weight than without, which also makes the linearity better.

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  • Color, Gradation (AREA)

Abstract

Selon la présente invention, un ensemble d'échantillons demi-teintes (18) prédéterminés est créé, chaque échantillon correspondant à un certain niveau d'intensité. Les ensembles d'échantillons demi-teintes enregistrés dans une unité mémoire (44). Un premier groupement de données éléments d'image (34) est fourni sous la forme d'une donnée d'image d'entrée. La donnée d'entrée est balayée élément d'image par élément d'image, et le niveau d'intensité de chaque élément d'image est lu. Pour accéder aux échantillons demi-teintes (18) prédéterminés, on utilise la position ligne et colonne avec le niveau d'intensité comme une adresse, pointant un certain élément d'image. La valeur d'intensité de cet élément d'image est lue et sortie comme un élément d'image au niveau d'un deuxième groupement de données (36) à envoyer à une imprimante (32). L'accès mémoire est réalisé uniquement à l'aide d'éléments matériel logique (42), augmentant ainsi la vitesse de traitement. Dans le cas d'images couleur, la couleur agit également comme une partie de l'adresse d'accès.
PCT/SE2000/000002 2000-01-03 2000-01-03 Dispositif et procede d'impression WO2001050236A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU29518/00A AU2951800A (en) 2000-01-03 2000-01-03 Printing device and method
PCT/SE2000/000002 WO2001050236A1 (fr) 2000-01-03 2000-01-03 Dispositif et procede d'impression

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PCT/SE2000/000002 WO2001050236A1 (fr) 2000-01-03 2000-01-03 Dispositif et procede d'impression

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WO2001050236A1 true WO2001050236A1 (fr) 2001-07-12

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003076197A1 (fr) * 2002-03-11 2003-09-18 Print Dreams Europe Ab Dispositif d'impression a actionnement manuel
DE102004021047B3 (de) * 2004-04-29 2005-10-06 Koenig & Bauer Ag Verfahren zum Vergleich eines Bildes mit mindestens einem Referenzbild

Citations (4)

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Publication number Priority date Publication date Assignee Title
US4722008A (en) * 1985-01-10 1988-01-26 Nippon Telegraph & Telephone Corporation Halftone picture processing apparatus
EP0488324A2 (fr) * 1990-11-28 1992-06-03 Dainippon Screen Mfg. Co., Ltd. Procédé et appareil pour la production d'images à demi-teinte
EP0498106A2 (fr) * 1991-02-08 1992-08-12 Adobe Systems Inc. Procédé d'attribution d'éléments d'images aux cellules d'une trame en demi-teintes
US5957593A (en) * 1993-11-12 1999-09-28 Tektronix, Inc. Halftone pattern geometry for printing high quality images

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4722008A (en) * 1985-01-10 1988-01-26 Nippon Telegraph & Telephone Corporation Halftone picture processing apparatus
EP0488324A2 (fr) * 1990-11-28 1992-06-03 Dainippon Screen Mfg. Co., Ltd. Procédé et appareil pour la production d'images à demi-teinte
EP0498106A2 (fr) * 1991-02-08 1992-08-12 Adobe Systems Inc. Procédé d'attribution d'éléments d'images aux cellules d'une trame en demi-teintes
US5957593A (en) * 1993-11-12 1999-09-28 Tektronix, Inc. Halftone pattern geometry for printing high quality images

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003076197A1 (fr) * 2002-03-11 2003-09-18 Print Dreams Europe Ab Dispositif d'impression a actionnement manuel
DE102004021047B3 (de) * 2004-04-29 2005-10-06 Koenig & Bauer Ag Verfahren zum Vergleich eines Bildes mit mindestens einem Referenzbild

Also Published As

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