Abstract:
A method of reducing the amount of black in an image is disclosed. The method is using a computer to reduce the amount of or eliminate the black in an original digital image. The major procedure is to increase the pixels of the original digital image (by four or nine times) and then change the color information of the pixels.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a method of reducing the amount of black in an image, such that a printer can print the image without or with only a little black ink (or toner). 
         [0003]    2. Description of the Related Art 
         [0004]    Generally, a common printer performs an automatic determination of an image for being printed according to a print command sent from a user end computer, after which it accordingly mixes in black ink (or toner) to achieve a grayscale effect, thereby saving the consumption of color ink (or toner) as well as achieving a better shadow detail effect. However, for certain situations, an image printed with black ink (or toner) is not desired. For example, when a user utilizes an optical pen (also known as an optical index/optical identification (OID) pen, please refer to http://www.giga.com.tw/english/productpen.htm for more details) to read a speech-purpose print code (mostly in the form of very tiny 2D barcodes) on a certain image, the efficiency of the OID pen may be affected if the image itself also contains a lot of black, since the speech-purpose print code is printed completely or primarily in black. 
         [0005]    In known prior art solutions, image processing software is utilized to convert the image from an RGB format into a CMYK format and to eliminate or reduce the K value in the CMYK format. However, one RGB value may correspond to multiple CMYK combinations. Therefore, when the converted image is sent to a printer end, the printer system will still process the remaining CMY values, and add a K value to obtain a shadow effect. Moreover, the printed image may look unbalanced because the K value (i.e. the shadow) of the original image is eliminated, while the brighter part remains unchanged. 
         [0006]    Therefore, there is a need to provide a method of reducing the amount of black so as to completely avoid the conversion mechanism of adding the K value performed by the printer system, such that the user can obtain a printed image without or with only a little black ink (or toner), thereby mitigating and/or obviating the aforementioned problems. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of the present invention to provide a method of reducing the amount of black in an image. 
         [0008]    To achieve the abovementioned objects, the method of reducing the amount of black in an image of the present invention comprises the following steps: 
         [0009]    Reading an original digital image, which comprises P original pixels, wherein 1≦P≦9,000,000,000, and each original pixel comprises three types of color information including the following: R color information referring to a red value; G color information referring to a green value; and B color information referring to a blue value, where: 
         [0000]      0≦R≦F, 0≦G≦F, 0≦B≦F, wherein 2 4 −1≦F≦2 32 −1;
 
         [0010]    Preparing a digital image under conversion, which comprises N×N×P pixels under conversion, wherein N is 2 or 3, and each original pixel corresponds to N×N pixels under conversion; and
       generating color information of the N×N pixels under conversion corresponding to each original pixel, wherein at least N×N pixels under conversion corresponding to one original pixel have been through a black reduction process, and the color information of the corresponding N×N pixels under conversion meets at least one of the following conditions: 0.8×F≦R≦F, 0.8×F≦G≦F or 0.8×F≦B≦F.       
 
         [0012]    If N=3, the color information of the nine corresponding pixels under conversion meets at least two of the following three conditions: 
         [0013]    Condition 1: (0.5×F≦R≦F and 0.8×F≦G≦F) or (0.8×F≦R≦F and 0.5×F≦G≦F); 
         [0014]    Condition 2: (0.5×F≦G≦F and 0.8×F≦B≦F) or (0.8×F≦G≦F and 0.5×F≦B≦F); and 
         [0015]    Condition 3: (0.5×F≦R≦F and 0.8×F≦B≦F) or (0.8×F≦R≦F and 0.5×F≦B≦F). 
         [0016]    If N=2, the color information of the four corresponding pixels under conversion is characterized in that: 
         [0017]    the color information of two of the four pixels under conversion meets at least one of the following three conditions: 
         [0018]    Condition 1: (0.5×F≦R≦F and 0.8×F≦G≦F) or (0.8×F≦R≦F and 0.5×F≦G≦F); 
         [0019]    Condition 2: (0.5×F≦G≦F and 0.8≦B≦F) or (0.8×F≦G≦F and 0.5≦B≦F); and 
         [0020]    Condition 3: (0.5×F≦R≦F and 0.8≦B≦F) or (0.8×F≦R≦F and 0.5≦B≦F); 
         [0021]    and 
         [0022]    the color information of two of the four pixels under conversion meets at least one of the following conditions: 
         [0000]      0.8×F≦R≦F, 0.8×F≦G≦F or 0.8×F≦B≦F.
 
         [0023]    Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    These and other objects and advantages of the present invention will become apparent from the following description of the accompanying drawings, which disclose several embodiments of the present invention. It is to be understood that the drawings are to be used for purposes of illustration only, and not as a definition of the invention. 
           [0025]    In the drawings, wherein similar reference numerals denote similar elements throughout the several views: 
           [0026]      FIG. 1  illustrates an environmental schematic drawing according to a first embodiment of the present invention. 
           [0027]      FIG. 2  illustrates an environmental schematic drawing according to a second embodiment of the present invention. 
           [0028]      FIG. 3  illustrates a flowchart according to the present invention. 
           [0029]      FIG. 4  illustrates a schematic drawing showing original pixels of an original digital image. 
           [0030]      FIG. 5  provides a table showing the R, G and B color information of the original pixels according to one embodiment of the present invention. 
           [0031]      FIG. 6  illustrates a schematic drawing showing pixels under conversion of a digital image under conversion according to the first embodiment of the present invention, wherein N=3. 
           [0032]      FIG. 7  illustrates a schematic drawing showing pixels under conversion of the digital image under conversion according to the second embodiment of the present invention, wherein N=2. 
           [0033]      FIG. 8  illustrates a schematic drawing showing one original pixel corresponding to nine pixels under conversion according to one embodiment of the present invention, wherein N=3. 
           [0034]      FIG. 9  provides a table showing the color information of nine pixels under conversion after passing through a black reduction process according to one embodiment of the present invention. 
           [0035]      FIG. 10  illustrates a schematic drawing showing one original pixel corresponding to four pixels under conversion according to one embodiment of the present invention, wherein N=2. 
           [0036]      FIG. 11  provides a table showing first color information of four pixels under conversion after passing through a black reduction process according to one embodiment of the present invention. 
           [0037]      FIG. 12  provides a table showing second color information of four pixels under conversion after passing through a black reduction process according to one embodiment of the present invention. 
           [0038]      FIG. 13  provides a table showing third color information of four pixels under conversion after passing through a black reduction process according to one embodiment of the present invention. 
           [0039]      FIG. 14  provides a table showing color information of nine pixels under conversion without passing through a black reduction process according to one embodiment of the present invention. 
           [0040]      FIG. 15  provides a table showing color information of four pixels under conversion without being through the amount of black reduction process according to one embodiment of the present invention. 
           [0041]      FIG. 16  illustrates a schematic drawing showing an OID pen reading a speech-purpose print code. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0042]    Please refer to  FIG. 1 , which illustrates an environmental schematic drawing according to a first embodiment of the present invention. 
         [0043]    A user can utilize a personal computer  10  to execute the method of reducing the amount of black in an image of the present invention. The computer  10  mainly comprises a processor  11  and a memory  12 . The memory  12  is stored with an application program  20 . In the present invention, the processor  11  executes the application program  20  so as to generate and perform the steps of the present invention. 
         [0044]    The computer  10  is connected to a printer  16  via either a wired connection or a wireless connection. The printer  16  is used for printing documents. 
         [0045]      FIG. 2  illustrates an environmental schematic drawing according to a second embodiment of the present invention. The user utilizes a near-end computer  81  to connect to a computer  10   a  (such as a network server) via a network  80  (such as the internet), such that the near-end computer  81  can use the application program  20  of the network server  10   a.  In the second embodiment, the printer  16  is connected to the near-end computer  81  via either a wired connection or a wireless connection. The point of these two different embodiments is that the user can utilize the computer to execute the application program  20 , and then utilize the printer  16  to print documents. 
         [0046]    Please refer to  FIG. 3 , which illustrates a flowchart according to the present invention. Please also refer to  FIGS. 1-2  as well as  FIGS. 4-16  for a comprehensive understanding of the present invention. 
       Step  301 : Reading an Original Digital Image  30 . 
       [0047]    The original digital image  30  comprises P original pixels  31 , wherein 1≦P≦9,000,000,000. A pixel is the minimum unit of a digital image (bitmap). For example, an 800×600 image is 800 pixels in width and 600 pixels in height. Therefore, an 800×600 digital image has a total of 800×600=480,000 pixels. Theoretically, P can be infinity; however, for current and foreseeable applications, it should be sufficient that P has a maximum of 9,000,000,000 to cover the usage of most digital images. 
         [0048]    For example, the user can obtain a digital image from his/her computer or from a website for the application program  20  to read. Please note that the digital image may not be recorded in a bitmap format (e.g., it may be recorded in a compressed JPG format). If that is the case, the digital image needs to be converted into the bitmap format first. In step  301 , the original digital image  30  can be a pre-processed digital image, such as an image converted from other formats, a reduced image, or an enlarged image. 
         [0049]    Each original pixel  31  comprises three types of color information including the following: R color information referring to a red value; G color information referring to a green value; and B color information referring to a blue value. R, G and B are the three primary colors for being displayed on a screen. Generally, each of the color information is represented in 8 bits ranging from 0 to 255. Currently, the color information can be represented in 4 bits, 8 bits, or 16 bits. Or, it may even be represented in 32 bits in the future. Therefore: 
         [0000]      0≦R≦F, 0≦G≦F, 0≦B≦F, wherein 2 4 −1≦F≦2 32 −1.
 
         [0050]    Please refer to  FIG. 4 , which illustrates a schematic drawing showing original pixels of an original digital image. For convenience&#39;s sake, in this embodiment, the original digital image  30  comprises four original pixels  31   a,    31   b,    31   c  and  31   d,  wherein each of the pixels comprises the R, G and B color information, as shown in  FIG. 5 . 
         [0000]    Step  302 : Preparing a digital image under conversion  40   a  or  40   b,  which comprises N×N×P pixels under conversion  41 , wherein N is 2 or 3, and each of the original pixels  31  corresponds to N×N pixels under conversion  41 . 
         [0051]    If N=3, please refer to  FIG. 6 , wherein each original pixel corresponds to nine pixels under conversion  41 . 
         [0052]    If N=2, please refer to  FIG. 7 , wherein each original pixel corresponds to four pixels under conversion  41 . 
         [0000]    Step  303 : Sequentially determining whether the original pixels  31   a,    31   b,    31   c  and  31   d  of the original digital image  30  requires reducing the amount of black. 
         [0053]    If yes, the method of the present invention performs step  304 . 
         [0054]    If no, the method of the present invention performs step  306 . 
         [0055]    For example, with regard to the original pixel  31   a  (RGB=22,20,30), because the brightness (12%) under its saturation (33%, i.e. “1-(the minimal color information/the maximal color information)”) is lower than a certain preset lowest brightness value (78%) of a print apparatus for adding a K value, the K value needs to be eliminated. 
         [0056]    With regard to the original pixel  31   b  (RGB=200,190,0), because the brightness (78%) under its saturation (100%) is higher than a certain preset lowest brightness value (55%) of a print apparatus for adding a K value, there is no need to eliminate the K value. 
         [0000]    Step  304 : Enhancing color saturation for the original pixel requiring reduction of the amount of black. 
         [0057]    Because the color saturation will be lowered after performing the black reduction process (step  305 ), it is suggested that the color saturation be enhanced before step  305  is performed. 
         [0058]    For example, the original color information of the original pixel  31   a  is: R=22, G=20 and B=30. After the color saturation enhancement, the color information becomes: R=20, G=15 and B=30. Because the technique of color saturation enhancement is a known prior art, there is no need for further description. 
         [0000]    Step  305 : Generating color information of the N×N pixels under conversion  41  corresponding to each original pixel  31 , wherein at least N×N pixels under conversion  41  corresponding to one original pixel  31  that has been through the black reduction process. 
         [0059]    Take the original pixel  31   a  after color saturation enhancement as an example, wherein R=20, G=15 and B=30: 
         [0060]    If N=3: 
         [0061]    Please refer to  FIG. 8 , which illustrates a schematic drawing showing the original pixel  31   a  corresponding to nine pixels under conversion  41   a ˜ 41   i.  Please also refer to  FIG. 9  for their color information. 
         [0062]    The color information of the three pixels under conversion  41   a,    41   f  and  41   h  is characterized as R=F and G=F, while their B values are equal to the B value of the original pixel  31   a.    
         [0063]    The color information of the three pixels under conversion  41   b,    41   d  and  41   i  is characterized as G=F and B=F, while their R values are equal to the R value of the original pixel  31   a.    
         [0064]    The color information of the three pixels under conversion  41   c,    41   e  and  41   g  is characterized as B=F and R=F, while their G values are equal to the G value of the original pixel  31   a.    
         [0065]    As shown in  FIG. 9 , in this embodiment, each of the original RGB values of the original pixel  31   a  is represented as three pixels under conversion. Because the color information of each pixel under conversion  41   a ˜ 41   i  has two full values (equal to F), the K value will not be shown during a printing process (wherein the printer will be converted to a CMYK format). 
         [0066]    As shown in  FIG. 9 , it is ensured that the K value will be eliminated in this embodiment, which is applicable for all types of print apparatuses. However, if the object is to reduce the K value, and each type of print apparatuses has its own conversion conditions, then the color information of the corresponding N×N (i.e. nine, if N=3) pixels under conversion meets at least two of the following three conditions: 
         [0067]    Condition 1: (0.5×F≦R≦F and 0.8×F≦G≦F) or (0.8×F≦R≦F and 0.5×F≦G≦F); 
         [0068]    Condition 2: (0.5×F≦G≦F and 0.8×F≦B≦F) or (0.8×F≦G≦F and 0.5×F≦B≦F); and 
         [0069]    Condition 3: (0.5×F≦R≦F and 0.8×F≦B≦F) or (0.8×F≦R≦F and 0.5×F≦B≦F). 
         [0070]    For example: 
         [0071]    The color information of the three pixels under conversion  41   a,    41   f  and  41   h  is characterized as R=0.5×F and G=0.8×F, while their B values are equal to the B value of the original pixel  31   a.    
         [0072]    The color information of the three pixels under conversion  41   b,    41   d  and  41   i  is characterized as G=0.5×F and B=0.8×F, while their R values are equal to the R value of the original pixel  31   a.    
         [0073]    The color information of the three pixels under conversion  41   c,    41   e  and  41   g  is characterized as B=0.8×F and R=0.5×F, while their G values are equal to the G value of the original pixel  31   a.    
         [0074]    After a practical experiment, if one of the RGB color information data of a pixel under conversion equals to or exceeds 0.5×F, and another equals to or exceeds 0.8×F, the object of reducing the K value can be achieved because it is assured that the brightness will be greater than or equal to 80% under any circumstances. 
         [0075]    If N=2, please refer to a first embodiment described hereinafter: 
         [0076]    Please refer to  FIG. 10 , which illustrates a schematic drawing showing the original pixel  31   a  corresponding to four pixels under conversion  41   j ˜ 41   n.  Please also refer to  FIG. 11  for their color information. 
         [0077]    The color information of the two pixels under conversion  41   j  and  41   n  is characterized as R=F and G=F, while their B values are equal to the B value of the original pixel  31   a.    
         [0078]    The color information of the two pixels under conversion  41   k  and  41   m  is characterized as B=F, while their R values and G values are equal to the R value and G value of the original pixel  31   a.    
         [0079]    That is, the B value of the original pixel  31   a  is represented as two pixels under conversion, while the R value and the G value of the original pixel  31   a  are represented as another two pixels under conversion. Because the color information of each pixel under conversion  41   j ˜ 41   n  has at least one full value (equal to F), the K value will not be shown during a printing process (wherein the printer will be converted to a CMYK system). As shown in  FIG. 11 , it is ensured that the K value will be eliminated in this embodiment. However, if the object is to reduce the K value, the method of the present invention will work similarly to what is described if N=3. That is: 
         [0080]    The color information of the two pixels under conversion  41   j  and  41   n  is characterized as (0.5×F≦R≦F and 0.8×F≦G≦F) or (0.8×F≦R≦F and 0.5×F≦G≦F), while their B values are equal to the B value of the original pixel  31   a.    
         [0081]    The color information of the two pixels under conversion  41   k  and  41   m  is characterized as 0.8×F≦B≦F, while their R values and G values are equal to the R value and G value of the original pixel  31   a.    
         [0082]    If N=2, please refer to a second embodiment described hereinafter: 
         [0083]    Please refer to  FIG. 10 , which illustrates a schematic drawing showing the original pixel  31   a  corresponding to four pixels under conversion  41   j ˜ 41   n.  Please also refer to  FIG. 12  for their color information. 
         [0084]    The color information of the two pixels under conversion  41   j  and  41   n  is characterized as G=F and B=F, while their R values are equal to the R value of the original pixel  31   a.    
         [0085]    The color information of the two pixels under conversion  41   k  and  41   m  is characterized as R=F, while their G values and B values are equal to the G value and B value of the original pixel  31   a.    
         [0086]    That is, the R value of the original pixel  31   a  is represented as two pixels under conversion, while the G value and the B value of the original pixel  31   a  are represented as another two pixels under conversion. Because the color information of each pixel under conversion  41   j ˜ 41   n  has at least one full value (equal to F), the K value will not be shown during a printing process (wherein the printer will be converted to a CMYK system). As shown in  FIG. 12 , it is ensured that the K value will be eliminated in this embodiment. However, if the object is to reduce the K value, the method of the present invention will work similarly to what is described if N=3. That is: 
         [0087]    The color information of the two pixels under conversion  41   j  and  41   n  is characterized as (0.5×F and 0.8×F≦B≦F) or (0.8×F≦G≦F and 0.5×F≦B≦F), while their R values are equal to the R value of the original pixel  31   a.    
         [0088]    The color information of the two pixels under conversion  41   k  and  41   m  is characterized as 0.8×F while their G values and B values are equal to the G value and B value of the original pixel  31   a.    
         [0089]    If N=2, please refer to a third embodiment described hereinafter: 
         [0090]    Please refer to  FIG. 10 , which illustrates a schematic drawing showing the original pixel  31   a  corresponding to four pixels under conversion  41   j ˜ 41   n.  Please also refer to  FIG. 13  for their color information. 
         [0091]    The color information of the two pixels under conversion  41   j  and  41   n  is characterized as B=F and R=F, while their G values are equal to the G value of the original pixel  31   a.    
         [0092]    The color information of the two pixels under conversion  41   k  and  41   m  is characterized as G=F, while their B values and R values are equal to the B value and R value of the original pixel  31   a.    
         [0093]    That is, the G value of the original pixel  31   a  is represented as two pixels under conversion, while the B value and the R value of the original pixel  31   a  are represented as another two pixels under conversion. Because the color information of each pixel under conversion  41   j ˜ 41   n  has at least one full value (equal to F), the K value will not be shown during a printing process (wherein the printer will be converted to a CMYK system). As shown in  FIG. 13 , it is assured that the K value will be eliminated in this embodiment. However, if the object is to reduce the K value, the method of the present invention will work similarly to what is described if N=3. That is: 
         [0094]    The color information of the two pixels under conversion  41   j  and  41   n  is characterized as (0.5×F≦R≦F and 0.8×F≦F) or (0.8×F≦R≦F and 0.5×F≦B≦F), while their G values are equal to the G value of the original pixel  31   a.    
         [0095]    The color information of the two pixels under conversion  41   k  and  41   m  is characterized as 0.8×F≦G≦F, while their R values and B values are equal to the R value and B value of the original pixel  31   a.    
         [0000]    Step  306 : Directly copying color information of the original pixel to its corresponding N×N pixels under conversion because there is no need for the black reduction process. 
         [0096]    If N=3: please refer to  FIG. 14 , which provides a table showing the color information of the original pixel  31   a  corresponding to that of nine pixels under conversion  41   a ˜ 41   i.    
         [0097]    If N=2, please refer to  FIG. 15 , which provides a table showing the color information of the original pixel  31   a  corresponding to that of four pixels under conversion  41   j ˜ 41   n.    
         [0098]    According to the abovementioned steps, the digital image under conversion  40   a  or  40   b  would become a converted digital image  50 . Because the black of the original digital image  30  has been eliminated or reduced in amount, its printout can, for example, be read by an optical pen  90 . The optical pen  90  is also known as an optical index/optical identification (OID) pen (please refer to http://www.giga.com.tw/english/productpen.htm for more details). Because the hardware is a known device, there is no need for further description. Please refer to  FIG. 16 . A speech-purpose print code  70  and the converted digital image  50  are printed on the same location. Although the speech-purpose print code  70  is still printed in black, the efficiency of utilizing the optical pen  90  to read the speech-purpose print code  70  can be significantly increased because the black of the converted digital image  50  has been eliminated or reduced in amount. 
         [0099]    Although the present invention has been explained in relation to its preferred embodiments, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed. For example, step  303  is not necessary. That is, all pixels can be processed by step  305 , such that the processed image would have more even brightness (because the brightness would be increased consistently). Otherwise, if some pixels are processed by step  305  (generally the brightness would be increased), and other pixels are processed by step  306  (the brightness and color remain unchanged), it might result in uneven brightness.