Classifications

• • 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
  • H04N1/40012—Conversion of colour to monochrome
• • 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
  • H04N1/46—Colour picture communication systems
  • H04N1/56—Processing of colour picture signals
  • H04N1/60—Colour correction or control
• • 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
  • H04N1/46—Colour picture communication systems
  • H04N1/56—Processing of colour picture signals
  • H04N1/60—Colour correction or control
  • H04N1/6097—Colour correction or control depending on the characteristics of the output medium, e.g. glossy paper, matt paper, transparency or fabrics

Definitions

• the invention relates to a method and an apparatus for converting source image data into target image data, in which source image data for generating a source print image are processed in at least a first color.
• Target image data for generating a target print image are generated in at least one second color different from the first color.
• Optimized image data is generated, which is fed to the output device.
• the optimization of the image data relates in particular to the possible color representation and the effect of the output image influencing factors.
• Such factors are, in particular when printers are used as output devices, the area coverage of the individual toner colors used for producing the printed image and their tone value curves.
• the area coverages and tone curves of all the printing colors used by the printer are taken into account.
• These inks are also referred to as primary colors and are known in printers
• Cyan, Magenta, Yellow, Black Print images produced with the aid of these primary colors are also referred to as CMYK images, where C is the color cyan, M is the color magenta, Y is the color yellow, i. Yellow, and K is the color black, i. Black, labeled.
• CMYK images where C is the color cyan, M is the color magenta, Y is the color yellow, i. Yellow, and K is the color black, i. Black, labeled.
• specially blended special colors can be used to produce printed images or to produce mixed images.
• the representation of the output image is Picture often poor.
• the representations of full-color photographs in the output with the help of black and white printers are sometimes no longer recognizable.
• the individual colors and shades should be well distinguishable from each other even after the output in one or more other colors to the viewer.
• a reduction in the colors used in the output of the image is no longer possible to the same degree as in the representation of the original image in full color and / or a special color
• the individual pictorial components should be used for the viewer be equally distinguishable as in an original image.
• RGB red, green, blue
• not all colors can be reproduced using the RGB color space. These colors include, in particular, the primary printing inks yellow and cyan of a full-color printer. Many spot colors can also not be described using the RGB color space.
• the document DE 694 21 018 T2 discloses a method and a device for the automatic color conversion of a source color into a destination color which, in a document to be reproduced, convert all areas corresponding to the source color into the designated color.
• Document DE 102 05 476 A1 discloses a process for the printing process transformation of color printing for black-and-white images, in which color values dependent on the device are taken into account during the transformation. From GB 2 213 674 A a conversion of RGB color values for displaying an image on a monitor into C-M Y-K color values for outputting a color image on a printer is known.
• the object of the invention is to specify a method and a device for converting source image data into target image data in which target image data for generating a target image in at least one second color different from the first color from source image data for generating a source image in at least one first color simple manner can be generated by the high-quality Dar ⁇ position of the target image is possible.
• the target image has the same brightness distribution as the source image, giving the viewer a similar visual impression.
• individual regions of the target image can be distinguished from each other in the same way as these regions in the source image.
• a second aspect of the invention relates to an apparatus for converting source image data into target image data.
• the source image data for generating a print image in at least one first color are processed by means of a data processing unit.
• the data processing unit generates target image data for generating a print image in at least one second color other than the first color.
• the data processing unit further determines with the aid of the source image data for each pixel of a Zielbil ⁇ a brightness value of the coloring of the source image in the region of the pixel. Furthermore, depending on the determined brightness value, the data processing unit generates target image data by which each pixel in a print image generated in the second color has the same brightness value as the brightness value determined for the respective pixel in the source image.
• target image data can be generated from the source image data, by means of which a target image can be output which produces similar contours, contrast and brightness impressions for the viewer, such as a source image generated with the aid of the source image data.
• Fig. 1 is a general block diagram for generating a target printing image according to the invention
• FIG. 2 is a flowchart for converting source image data into target image data, taking into account properties of a target printer and IST printer according to a first embodiment of the invention.
• FIG. 3 shows a flow chart according to FIG. 3 for generating target image data from source image data according to a second embodiment of the invention.
• FIG. 1 shows a general block diagram showing the processing according to the invention of source image data for generating a printed image with the aid of a printer.
• Source image data 10 have already been optimized for generating a printed image with the aid of a desired printer on a standard printing material.
• the target printing material is a concrete carrier material to be used, on which a printed image is to be produced.
• the color values of the target printer and the reproduction properties of the printing material 14 are also taken into account when processing the source image data for generating the target image data.
• the IST printer is a printer on which a target image is to be output, the optical impression of which is at least approximated to a print image output by means of the source image data by a desired printer.
• a brightness value for each pixel of the target image to be generated is determined with the aid of the source image data 10 as a function of the known color values of the target printer and the properties of the target printing material 14.
• target image data are generated taking into account the color values of the actual printer and the properties of the actual printing material.
• target image data generated in the processing process 12 are rasterized taking into account the output properties of the IST printer and a print data stream is generated. This print data stream is fed to a printer, not shown, which generates a print image on the actual print substrate in a printing process 20.
• FIG. 2 shows a flowchart for converting source image data into target image data according to a first embodiment of the invention.
• the sequence is started in step S10.
• the printer-dependent color values of the desired primary colors of the desired printer are determined in full tone in step S12. These color values are stored, for example, in a memory area, from which they are read out in step S12. Subsequently, in the
• Step S16 determines the CIEXYZ color values of these target primary colors. Based on the color values of the desired printing substrate determined in step S16, the CIEXYZ color values of the desired printing substrate are determined in step S18. In step S19, the tone value curves of the target primary colors in the source image are then determined. From the image data Then, in step S20, the areal extents of the primary color at each pixel are determined.
• a brightness value of the target composite color is determined from the determined CIEXYZ color values of the target primary colors of the printer in full tone, from the determined CIEXYZ color values of the target And the areal coverage and tone curves of the target primary colors in the source image. Further, in step S24, the tonal value curve of the actual color and, in step S26, the color values and the brightness of the color used on the actual printing material are determined.
• step ⁇ 28 Based on the brightness value determined in step S22, in step ⁇ 28 the actual color as well as the color values determined in step S26 and the brightness of the color used on the actual printing substrate are dependent on the tone color gradient determined in step S24
• Target print image determined.
• the brightness of the desired mixed color in the source pixel corresponds to the brightness of the color used in the target pixel.
• target image data are generated which are stored in step S30.
• the target image data may be transmitted directly to a printer.
• steps S12 to S20, S24 and S26 may be performed in another suitable order, e.g. be processed one after the other at the beginning of the process.
• FIG. 3 is a flowchart for converting source image data into target image data by means of the inventive method. driving according to a second embodiment shown.
• step SI10 the process is started.
• step S112 the variable i is assigned the value 0.
• step S114 the pixel with the variable i is selected.
• the first pixel of the target image to be generated is selected, ie the pixel BO.
• step S116 an area corresponding to the target pixel Bi in the source image is then determined.
• step S118 it is then determined which colors are included in the range determined in step S11 ⁇ and which color portion each of these colors has.
• the color fraction is preferably the area of the respective base color or the respective mixed color, which is visible when viewing the area.
• the respective color content is preferably determined as a percentage of color.
• step S120 the brightness of the source image in the region of the target pixel Bi is determined.
• the reflection properties of the paper and the areal coverage of the paper, ie the unprinted area in the area of the destination pixel Bi, are taken into account when determining the brightness Y for this destination pixel Bi.
• step S122 the areal coverage FD of the target image in the pixel Bi is determined to produce the same brightness Y in the target pixel Bi as in the corresponding area in the source image.
• the determined area coverage degree FD is used as a target image parameter for generating the target image and stored.
• step S124 it is checked in step S124 whether the pixel Bi is the last pixel of the target image. If so, the process is ended in step S126. Becomes determined in step S124 that the pixel Bi is not the last pixel, the process is continued in step S114 and repeated until the brightness value Y and the area coverage FD for each target pixel Bi point of the target image has been determined.
• the differences in color and brightness existing in the source image can be clearly distinguished even when the target image is viewed, if the source image contains several colors and the target image is reproduced only in one color.
• the brightnesses can be graded in the same way as in the optimal output of the source image, so that comparability of the color differences is also possible in the single-color output of the image.
• the determination of the brightness can not be done pixel-by-pixel but object-by-object.
• the brightness of a letter specified by means of a font and of a graphic object determined by means of a vector can be determined.
• the brightness of the source image can also be determined for individual objects contained in this source image in order to be able to display these objects in the target image with the same brightness. Also, combinations of the described possibilities for determining the brightness of regions of the source image are possible.
• the tone curves of the printer are not known and / or the brightness of the printing material, ie the Rinshizada, unknown, also standard values or standard values, eg from ISO 13647, for determining the brightness of Objects or areas in the source image and to determine the surface coverage in the target image.
• standard values or standard values eg from ISO 13647
• current standards brightness values for mixed colors To determine the brightness value of a mixed cyan and magenta color, either measure the brightness or use an existing reference value.
• the CIELAB color space according to ISO 2846 is generally used.
• ISO 2846 specifies a number of properties for standard-compliant printing inks. Furthermore, in particular when reproducing an image with the aid of a printer, the properties of the support material and the color rendering properties of the printer or copier are decisive for the visual effect of the print image on the viewer.
• the influences of the carrier material on the optical effect of the print image must also be produced and the tone curves of the target printer and the IST printer are taken into account.
• the properties of the support material when determining the brightness value when coated papers, LWC papers, uncoated papers or uncoated yellowish papers are used as support material.
• the special color of the carrier material when using carrier material which does not have the color white, the special color of the carrier material must be taken into account.
• the advantage of using the CIELAB color space is that this color space is visually equally spaced.
• other visually equally spaced color space can be used as a basis for the invention. the. If the color spaces are of equal length, a distance measure ⁇ E * between two colors or between a mixed color and a base color can be determined. This distance measure serves as a measure of the perceived differences between the target and actual colors. As a result, these perceived differences can be quantified.
• all possible colors, including spot colors can be arranged in the CIELAB color space. Special measurements make it relatively easy to determine the properties of a spot color to determine the CIELAB properties of this spot color.
• Toner value can be determined. Furthermore, the fact that the RGB color space is visually not equally distant means that the brightness of a region in the source image is difficult to determine, which makes the determination of the required surface coverage in the target ink very complicated.
• RGB color space can not be defined and specified because they are out of the definition range of the RGB color space.
• non-specifiable colors include, above all, special colors and the full tone yellow and cyan of the four color screen printing.
• Method is a calculation of the gray scale shares beechi ⁇ ger mixed colors including special colors simple possible.
• the calculation of the gray value components can take place taking into account the properties of a desired printing system for which the printed image was originally optimized.
• the properties of the printing system or the properties of a class of printing systems can be taken into account when generating target image data so that the color differences in the target print image are comparable to those in the source print image.
• the source print data for the output of a source print image are optimized on a source image printer, wherein the source image data for the output of the source print image can be specially adapted with the aid of the source image printer.
• target image data for outputting a target image on a target image printer are generated from the source image data, whereby the source image and the target image can also have different resolutions.
• the method according to the invention can also be used advantageously if the source image printer of the target image printer only differs in the ink used.
• the source image printer can use a first print color and the target image printer can use a second print color other than the first print color.
• the optical effect of these printing inks differ naturally.
• the method according to the invention then serves to produce a target image that is comparable in terms of the visual impression to the viewer.
• the erfindungsge ⁇ Permitted method can also be used advantageously when the source image printer in particular has three required for full-color printing basic colors cyan, magenta, yellow and black and / or a special color.
• the brightness of the mixed color can be determined taking into account the dot gain. the.
• the tone value for the same area in the target image can be determined depending on the target image color.
• the reflection factor of a four-color printed area can be calculated using the following formula:
• Rp x Rp * (FDp + R Q * FDQ + RM * FD M + R ⁇ * FD ⁇ + R K * FD K +
• Rp is the reflection factor of the carrier material, preferably the paper,
• R Q to RcMYK give the reflection factors in each case in the index, optionally superimposed printed layers,
• FD Q to FDQ] V [YK are the surface coverages of the layers, which may be printed one above the other in the index.
• the reflection factors R of the color layers printed on one another can be calculated at least approximately by multiplying the reflection factors of the individual layers.
• the reflection factors of the overprinted colors can also be measured or read from tables / standards.
• the reflection factors of the solid tones on the paper are calculated by dividing by the reflection factor of the unprinted paper. This avoids the fact that the reflection properties of the carrier material are taken into account several times in the case of superposition printing in several full tones.
• the solid tones are the primary colors CMYK of the printer, which stand for cyan, magenta, yellow and black.
• the determination of the reflection factor of a mixed color of cyan and magenta on a support material with the reflection factor Rp is calculated according to the following formula:
• R CM (R C / R P ) • (R M / R p )
• the coverage factors FD indicate the probabilities with which the corresponding primary color or mixed color is present at a particular location. Thus, the probability of not finding this color or mixed color at a particular location or in a particular area can be given by 1-FD.
• the area coverage factor FD can be determined for any desired mixed color. For example, the probability of the area coverage for a mixed color of cyan and magenta is calculated as follows:
• FDMic FD C • FD M • (1 - FDy) • (1 - FD K )
• This area coverage which is actually generated on the carrier material, is determined by adding the dot gain to the nominally controlled area coverage.
• the Tonwertzuddlingkurven for the textile dyes eg C, M, Y, K
• the process according to the invention for converting colored image constituents of a source image into optically identical monochrome representations in a target image is explained below for two colors Pantone 185U and Pantone Reflex Blue U which are not printed on one another in a company logo.
• the company logo should be printed with the help of a black and white printer.
• the area coverage of the Pantone 185U color is given as 50% in the source image data.
• a dot gain of 20% is determined for a surface coverage of 50%, so that the actual area coverage of the Pantone 185U color is 70%.
• an actual area coverage of 70% is achieved, whereby on 30% of the area the brightness of the paper is visible.
• the area printed with the color Pantone Reflex Blue U is printed with a coverage of 100%.
• the brightness value Y of the color Pantone 185U is 25, the brightness value of the color Pantone Reflex Blue U is 9 and the brightness Y of the paper on which the source print image should be generated is 90.
• As support material for the target printer on which the company logo in black and white is 86.
• the brightness value of the target ink black is 2.
• the resulting brightness value of the surface dyed with Pantone 185U, which is 70% with the color Pantone 185U and 30% with the brightness of the Textils is colored, is 44.5.
• the actual flat coverage for this area must be at 40% and for the area originally to be colored with Pantone Reflex Blue U at the flat coverage ratio of 85% black be colored.
• the flat coverage ratios for driving the target printer are determined on the basis of the tone value curve of the target printer, which are then taken over into the target image data. For the originally partially to be inked with Pantone 185U flat results then a flat coverage level of about 30% black and for the ur ⁇ bluntly with Pantone Reflex Blue U einarbende flat a flat coverage of about 65%.
• a printed image is then rasterized by means of a halftone process, whereby the area to be inked with Pantone 185U is colored to a degree of 40%, while the area originally to be inked with Pantone Reflex Blue U is 85% colored with black toner ,
• the brightness of a region in the source image can also be determined directly by using R Y as a measure of the brightness of the base and mixed colors instead of the reflection factor R Y.
• the area in the source image is, for example, the area of a pixel of the target image in the source image.
• the brightness for a range is then calculated according to the following formula:
• Y R Yp * (FDp + Yc * FD c + YM * FD M + Y ⁇ * FD ⁇ + Y ⁇ ⁇ * FD K +
• Y is the brightness of a base color or a mixed color of the base color or mixed color specified in the index
• F ⁇ special are the area coverage of the spot color.
• the CIELAB color values include a value labeled L, which indicates the brightness of the color.
• L indicates the brightness of the color.
• Brightness values directly calculate the Y-brightness values.
• a surface coverage ratio can be determined by comparison with the brightness value of the base color available on the target printer depending on the paper properties and the tone curves of the target image printer by which the target image when viewed causes similar contour differences and a similar visual impression on the viewer, such as an image generated with the source image printer.
• the source image printer is also referred to as a target printer and the target image printer as an IST printer.

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• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Facsimile Image Signal Circuits (AREA)
• Color Image Communication Systems (AREA)
• Image Processing (AREA)
• Color, Gradation (AREA)
• Color Electrophotography (AREA)

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• 2004
  • 2004-09-15 DE DE102004044647A patent/DE102004044647A1/de not_active Withdrawn
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  • 2005-09-08 EP EP05792241A patent/EP1800467A2/de not_active Ceased
  • 2005-09-08 US US11/574,681 patent/US20080094644A1/en not_active Abandoned
  • 2005-09-08 CN CN2005800310083A patent/CN101019412B/zh not_active Expired - Fee Related
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