Patent Publication Number: US-10780712-B2

Title: Drawing apparatus, method of drawing, and recording medium

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus and a method of drawing, and a recording medium. 
     2. Description of the Related Art 
     A nail drawing apparatus or nail printer is known that draws any designs chosen by a user on finger nails of the user (for example, Japanese Translation of PCT International Application Laid-Open No. 2003-534083). 
     Users can readily enjoy nail print with such an apparatus without visiting nail salons. 
     Human nails, which are the target of a nail printer, have an overall round and curved shape in which the right and left edges in the width direction are sunken and the central area is bulged. 
     Thus, the image (nail design) to be drawn may have varying print density or may be stretched or distorted depending on the tilt of the surface at the edges of the nail. 
     Drawing an image on a nail without such a variation in print density or stretching and distortion requires curved surface correction on the data of the image to be drawn, satisfactory resolution at the end regions of the nail in the width direction, and appropriate decimation of the data of regions without curved surface correction. To achieve such a drawing, the resolution of the entire nail surface including an area without curved surface correction, i.e., the relatively flat central area of the nail in the width direction, should be matched with the resolution of the end regions of the nail in the width direction, which receives curved surface correction. This causes an increase in volume of the image data compared to that of image data without curved surface correction. Thus, the memory for storing the image data for drawing with curved surface correction must have a large size compared to that without curved surface correction. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a drawing apparatus, a method of drawing, and a recording medium that can advantageously draw patterns on a nail with stable print density, without distortion at the end regions of the nail in the width direction, and without an increase in the volume of the drawing data. 
     According to an embodiment of the present invention, a drawing apparatus includes: a drawing head drawing a pattern on a surface of a target nail of a finger or toe; and a processor, wherein the processor controls the drawing head to scan a plurality of times across an area on the surface of the nail and to draw the pattern on the area during each of the plurality of scanning operations of the drawing head based on a curvature of the target nail. 
     According to an embodiment of the present invention, a method of drawing a pattern on the surface of a target nail of a finger or a toe using a drawing apparatus having a drawing head includes: performing a first control including controlling the drawing head to scan a plurality of times across an area on the surface of the target nail; and performing a second control including controlling the drawing head whether or not to draw the pattern on the area during each of the plurality of scanning operations based on the curvature of the target nail. 
     According to an embodiment of the present invention, a non-transitory readable recording medium storing a program for a drawing apparatus including a drawing head, causing a processor of the drawing head to execute a process of: controlling the drawing head to scan a plurality of times across an area on the surface of a nail and to draw a pattern on the area during each of the plurality of scanning operations in accordance with the curvature of the nail. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1A  is a front view of a drawing apparatus according to an embodiment.  FIG. 1B  is a side view of the internal configuration of the drawing apparatus illustrated in  FIG. 1A . 
         FIG. 2  is a block diagram of essential components of the control configuration of the drawing apparatus according to an embodiment. 
         FIG. 3  is a plan view of an example nail that is a target of drawing. 
         FIG. 4A  illustrates the curvatures and the correction factors corresponding to the curvatures.  FIG. 4B  illustrates images of nails having different curvatures. 
         FIG. 5  illustrates the correspondence between positions at the edge of the nail and the correction factors. 
         FIG. 6  is a schematic view of shape correction conducted on image data of a nail design. 
         FIG. 7A  illustrates an example unit region.  FIG. 7B  illustrates an example jet control table. 
         FIG. 8A  illustrates example jet control during scanning at a correction factor “1.”  FIG. 8B  illustrates example jet control during scanning at a correction factor “2.”  FIG. 8C  illustrates example jet control during scanning at correction factor “3.”  FIG. 8D  illustrates example jet control during scanning at correction factor “4.” 
         FIG. 9  is a schematic view of print density correction for drawing. 
         FIG. 10  illustrates jet control according to a modification. 
         FIG. 11  is a flow chart illustrating a drawing process according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A nail printer  1  or nail drawing apparatus and a method of drawing a pattern with the nail printer or nail drawing apparatus according to embodiments of the present invention will now be described with reference to  FIGS. 1 to 11 . 
     The following embodiments involve various technically preferred limitations for accomplishing the present invention. The scope of the invention, however, should not be limited to the embodiments and drawings. 
     The target of the nail printer  1  according to the embodiments described below is the surface of a nail of a finger. The target of the present invention may be any other surface, for example, the surface of a nail of a toe. 
       FIG. 1A  is a front view of the internal configuration of a nail printer  1 .  FIG. 1B  is a side view of the internal configuration of the nail printer  1  illustrated in  FIG. 1A . 
     With reference to  FIGS. 1A and 1B , the nail printer  1  according to this embodiment includes a drawing unit  40  including a drawing head  41  as a drawing tool. The nail printer  1  is an inkjet printer that draws a pattern on a nail T of a target finger U 1 . 
     The nail printer  1  includes a case  2  and a body  10  disposed in the case  2 . 
     A cover  23  that can be opened for replacement of the drawing head  41  of the drawing unit  40  is disposed at the upper end of a side face of the case  2 . The cover  23  turns from a closed position to an open position, as illustrated in  FIG. 1 , for example, around a hinge. 
     An operating unit  25  (see  FIG. 2 ) is disposed on the upper face or top panel of the case  2 . 
     The operating unit  25  is an input unit operated by the user to enter various input operations. 
     The operating unit  25  includes, for example, a power button for turning on the power of the nail printer  1 , a stop button for stopping the operation of the nail printer  1 , a design selection button for selecting a design to be drawn on the nail T, a drawing button for instructing the start of drawing, and an operating button (not shown) for entering various input operations. 
     A display  26  is disposed in the central area of the upper face or top panel of the case  2 . 
     The display  26  is a flat display, for example, a liquid crystal display (LCD) or an organic electroluminescent display. 
     In this embodiment, the display  26  appropriately displays, for example, a nail image (an image of the target finger U 1  including the nail T) acquired by capturing an image of the target finger U 1 , an image of the outline of the nail T included in the nail image, a design selection menu for selecting the design of the image to be drawn on the nail T, a thumbnail image for confirming the design, and an instruction menu for displaying various instructions. 
     The surface of the display  26  may be integrated with a touch panel for receiving various input operations. 
     The body  10  has a shape of a substantial box. The body  10  includes a lower casing  11  disposed inside the case  2  in the lower area and an upper casing  12  disposed inside the case  2  in the upper area above the lower casing  11 . 
     The lower casing  11  will now be described. 
     The lower casing  11  includes a back panel  111 , a bottom panel  112 , right and left side panels  113   a  and  113   b , an X-shifting-stage case  114 , a Y-shifting-stage case  115 , and a partition  116 . 
     The bottom edges of the side panels  113   a  and  113   b  are connected to the left and right edges of the bottom panel  112 , respectively, such that the side panels  113   a  and  113   b  are in a standing position with respect to the bottom panel  112 . 
     The lower portion of the back panel  111  sinks in two steps toward the front in the direction fingers are to be inserted. The lower portion of the back panel  111  is connected to the front edge of the bottom panel  112 . The back panel  111  partitions the space defined by the bottom panel  112  and the side panels  113   a  and  113   b  into front and rear compartments. The space defined behind the depressed back panel  111  serves as the X-shifting-stage case  114  and the Y-shifting-stage case  115  (see  FIG. 1B ). The X-shifting-stage case  114  accommodates an X-shifting stage  45  of the drawing unit  40  while the drawing unit  40  shifts forward in the direction fingers are to be inserted. The Y-shifting-stage case  115  accommodates a Y-shifting stage  47  of the drawing unit  40 . 
     The partition  116  is disposed inside the lower casing  11  to partition the space in the inner front side of the lower casing  11  (the space defined by the back panel  111 , the bottom panel  112 , and the side panels  113   a  and  113   b  at the front in the direction fingers are to be inserted) into upper and lower compartments. The partition  116  is substantially horizontally disposed. The left and right edges of the partition  116  are connected to the side panels  113   a  and  113   b , respectively. The rear end portion of the partition  116  is connected to the back panel  111 . 
     The lower casing  11  is integrated with a finger holder  30  (see  FIG. 1B ). The finger holder  30  includes a finger receiver  31  that receives the finger corresponding to the target nail T on which an image is drawn (this finger is hereinafter referred to as “target finger U 1 ”) and a finger space  32  where the fingers other than the target finger U 1  (which are hereinafter referred to as “non-target fingers U 2 ”) are placed. 
     The finger receiver  31  is disposed above the partition  116  and in the substantial middle of the lower casing  11  in the width direction. The lower compartment of the lower casing  11  partitioned by the partition  116  defines the finger space  32 . 
     For example, to draw an image on the nail T of the ring finger, the ring finger or target finger U 1  is inserted into the finger receiver  31  and the other four digits or non-target fingers U 2  (thumb, index finger, middle finger, and little finger) are inserted into the finger space  32 . 
     With reference to  FIGS. 1A and 1B , the finger receiver  31  is an opening in the front face (in the direction fingers are to be inserted) of the lower casing  11 . The bottom of the finger receiver  31  is partitioned by a finger rest  116   a , which is a portion of the partition  116 . The target finger U 1  having the target nail T is placed on the finger rest  116   a  in the XY plane. 
     The finger receiver  31  has a window (not shown) at the top to expose the nail T of the target finger U 1  inserted into the finger receiver  31 . 
     Front walls  31   f  (see  FIG. 1A ) blocking the front face of the lower casing  11  are vertically disposed on the upper face of the partition  116  at the two ends of the front face of the lower casing  11 . A pair of guiding walls  31   g  (see  FIG. 1A ) is vertically disposed on the upper face of the partition  116 . The guiding walls  31   g  define a space that tapered from the central areas of the front walls  31   f  toward the finger receiver  31  to guide the target finger U 1  into the finger receiver  31 . 
     The user can pinch the partition  116  with the target finger U 1  in the finger receiver  31  and the non-target fingers U 2  in the finger space  32 . This stabilizes the target finger U 1  disposed in the finger receiver  31 . 
     A home area  60  for holding the drawing head  41  during a standby mode is provided adjacent to the finger receiver  31  (on the right in  FIG. 1A ) on the upper face of the lower casing  11  within the movable region of the drawing head  41  described below. 
     An inkjet maintenance unit is disposed in the home area  60  facing the drawing head  41  disposed in the home area  60  during the standby mode. The inkjet maintenance unit includes, for example, a cleaning mechanism (not shown) for cleaning the ink jet (nozzle face) of the drawing head  41  and a cap mechanism (not shown) for maintaining a moist state of the ink jet (nozzle face). 
     The inkjet maintenance unit may be disposed at any other position in the home area. 
     The drawing unit  40  includes a drawing head  41 , a support  44  that supports the drawing head  41 , an X-shifting stage  45  that shifts the drawing head  41  in the X or right-left direction of the nail printer  1  in  FIG. 1A , an X-direction shift motor  46 , a Y-shifting stage  47  that shifts the drawing head  41  in the Y or front-back direction of the nail printer  1  in  FIG. 1B , and a Y-direction shift motor  48 . 
     The drawing head  41  is supported by a head holder  43  and disposed on the support  44  according to this embodiment. 
     The drawing head  41  is of an integrated cartridge type that includes ink cartridges (not shown), for example, for yellow (y), magenta (M), and cyan (C) inks integrated with ink jets (not shown) disposed on a plane facing the nail T (the lower face in this embodiment illustrated in  FIG. 1A ) on which a pattern is to be drawn. The ink jet includes nozzle arrays each including multiple nozzles that jet different color inks. The drawing head  41  jets microdroplets of ink from the ink jet directly onto the drawing surface of the target nail T to draw a pattern. The nozzles jetting inks each include a piezoelectric device (not shown). The jet of the ink from each nozzle is independently controlled through a drawing control process executed by a processor  81  described below. 
     The drawing head  41  may jet ink of any color besides the three colors mentioned above. Other ink cartridges and ink jets for other colors of ink may also be provided. 
     The nozzles of the drawing head  41  may have any configuration that can independently control the ink jet, besides that including piezoelectric devices. 
     For example, the nozzles may each include heaters for thermal nozzle control. 
     The support  44  is fixed to a X-direction shifter  451  fixed to the X-shifting stage  45 . The X-direction shifter  451  shifts in the X direction along a guide (not shown) on the X-shifting stage  45  by the driving force of the X-direction shift motor  46 . This shifts the drawing head  41  fixed to the support  44  in the X or right-left direction of the nail printer  1  in  FIG. 1A . 
     The X-shifting stage  45  is fixed to a Y-direction shifter  471  of the Y-shifting stage  47 . The Y-direction shifter  471  shifts in the Y direction along a guide (not shown) on the Y-shifting stage  47  by the driving force of the Y-direction shift motor  48 . This shifts the drawing head  41  fixed to the support  44  in the Y or front-back direction of the nail printer  1  in  FIG. 1B . In this embodiment, the X-shifting stage  45  is an assembly of the X-direction shift motor  46 , ball screws, and a guide (not shown), and the Y-shifting stage  47  is an assembly of the Y-direction shift motor  48 , ball screws, and a guide (not shown). 
     In this embodiment, the X-direction shift motor  46  and the Y-direction shift motor  48  constitute an XY driver or head shifter  49  that drives the drawing head  41  in the X and Y directions. 
     The drawing head  41 , the X-direction shift motor  46 , and the Y-direction shift motor  48  of the drawing unit  40  are connected to the processor  81  of a controller  80  described below and are controlled under a drawing control process executed by the processor  81 . 
     An image capturing unit  50  includes an image capturing device  51  and lighting devices  52 . 
     The lighting devices  52  of the image capturing unit  50  illuminate the nail T and the target finger U 1  inserted in the finger receiver  31  and exposed through the window. The image capturing device  51  captures an image of the target finger U 1  and acquires a nail image or an image of the target finger U 1  including the nail T. 
     The image capturing device  51  and the lighting devices  52  according to this embodiment are disposed on the upper casing  12 , as illustrated in  FIGS. 1A and 1B . 
     In detail, the image capturing device  51  and the lighting devices  52  of the image capturing unit  50  are disposed on the bottom face of a substrate  13  disposed on the upper casing  12  so as to face the partition  116 . 
     The image capturing device  51  and the lighting devices  52  may be disposed at any position other than those illustrated in the drawings on the substrate  13 . 
     The image capturing device  51  is, for example, a compact image capturing device including a solid-state image sensor provided with approximately 2 million or more pixels and a lens. 
     In this embodiment, the image capturing device  51  of the image capturing unit  50  captures a nail image or an image of the target finger U 1  including the nail T. 
     The nail-information selecting process described below detects the positions and shapes or outlines of the target finger U 1  and the target nail T, and the aspect ratio of the nail T in the nail image. 
     The lighting devices  52  are, for example, white LEDs. 
     In this embodiment, four lighting devices  52  are disposed on the right, left, front, and back of the image capturing device  51  so as to surround the image capturing device  51 . The lighting devices  52  emit light downward to illuminate the image-capturing area beneath the image capturing device  51 . 
     Any number of lighting devices  52  may be disposed at any positions besides those illustrated in the drawings. 
     The image capturing unit  50  is connected to the processor  81  (see  FIG. 2 ) of the controller  80  described below and controlled by the processor  81 . 
     Image data of nail images captured by the image capturing unit  50  is stored in a nail-image memory area  821  of a memory  82  described below. 
     The controller  80  is, for example, disposed on the substrate  13  on the upper casing  12 . 
       FIG. 2  is a block diagram of essential components of the control configuration according to this embodiment. 
     With reference to  FIG. 2 , the controller  80  is a computer including a processor  81  and a memory  82 , where the processor  81  includes a central processing unit (CPU) (not shown), and the memory  82  includes a read only memory (ROM) and a random access memory (RAM) (both not shown). 
     The memory  82  stores various programs and data items for operating the nail printer  1 . 
     In detail, the ROM of the memory  82  stores programs, such as a nail-information detecting program for detecting the position and shape or outline of the target finger U 1 , the position and shape or outline of the nail T, and the aspect ratio and other parameters of the nail T, a drawing-data generating program for generating drawing data from image data on a nail design subjected to curved surface correction, and a drawing program for executing a drawing process. These programs are executed by the controller  80  to comprehensively control the components of the nail printer  1 . 
     The memory  82  according to this embodiment includes a nail-image memory area  821  storing nail images of the nail T of the target finger U 1  captured by the image capturing unit  50 , a nail-information memory area  822  storing nail information (which includes the outlines of the target finger U 1  and the nail T and the aspect ratio of the nail T) detected through the nail-information detecting process executed by the processor  81 , a nail-design memory area  823  storing image data (also referred to as “design data”) on nail designs to be printed on the target nail T, and a correction-data memory area  824  storing data required for curved surface correction on the drawing data executed by the processor  81  through a drawing-data generating process. 
     The processor  81  executes an imaging control process, a nail-information detecting process, a drawing-data generating process, a drawing control process, and a display controlling process. The CPU of the processor  81  operates to function as an imaging controller, a nail-information detector, a drawing-data generating process unit, a drawing controller, or a display controller in cooperation with the programs stored in the ROM of the memory  82 . 
     The processor  81  executes the imaging control process to control the image capturing device  51  and the lighting devices  52  of the image capturing unit  50  and capture an image of the target finger U 1  placed in the finger receiver  31  (hereinafter, an image of the target finger U 1  including the nail T is referred to as “nail image”) with the image capturing device  51 . 
     Image data on the nail image captured by the image capturing unit  50  is stored in the nail-image memory area  821  of the memory  82 . 
     Detection of nail information including the outlines of the target finger U 1  and the nail T and the aspect ratio of the nail T in a nail image captured by the image capturing unit  50  will now be explained. The nail information detected in a nail image may be any other information, for example, the curvature of the nail T. 
     The nail-information detecting process executed by the processor  81  detects the outline of the finger defining the area of the target finger U 1 , the outline or shape of the nail T defining the area of the target nail T, and the curvatures indicating the curvature of the target nail T in the width direction, in a nail image including the target finger U 1  including the nail T captured by the image capturing device  51  of the image capturing unit  50 . 
     Nail information including the shapes or outlines of the target finger U 1  and the nail T is detected through the nail-information detecting process on the basis of, for example, the color difference between the target finger U 1  and nail T and the background (the finger rest  116   a  in this embodiment). The boundary between the nail T and the skin of the target finger U 1  is detected on the basis of the color difference between the nail T and the target finger U 1  and/or the shades to determine the shape or outline of the nail T. 
     In the case where the image capturing unit  50  captures a plurality of nail images by capturing operations while the lighting devices  52  emits light in a different angle during each capturing operation, the nail-information detecting process executed by the processor  81  determines the curvature of the nail T in the width direction on the basis of the darkness of the shades appearing in the nail image. The curvature includes information corresponding to the curvature of positions at predetermined intervals in the horizontal direction of the surface of the nail T, i.e., the tilt of the surface of the nail T to the horizontal direction, as illustrated in  FIG. 4  described below. 
     The nail information may be detected through any other method besides the method of detecting nail information through the nail-information detecting process explained above. The curvature is determined through the nail-information detecting process. Alternatively, the curvature may be determined through any other means, for example, the curvature may be preliminarily set to a standard value that is variable by the user. 
       FIG. 3  is a schematic view of the target nail T. 
       FIG. 3  includes a top plan view of the surface of the target nail T and a front view of the nail T from the tip of the nail T, where w is the apparent width of the surface of the nail viewed from the top. 
     The area “Ar_N” is the relatively flat central area of the nail in the width direction that requires no curved surface correction, and the left end area “Ar_L” and the right end area “Ar_R” are curved areas requiring curved surface correction and respectively reside on the left and right ends of the nail in the width direction. The areas “Ar_L” and “Ar_R” requiring curved surface correction each have a width of approximately 3 mm. The width of the areas “Ar_L” and “Ar_R” can be preliminarily determined as a default value or may vary depending on the curvature of the nail T. 
     The nail-information detecting process executed by the processor  81  may precisely detect the curvature of each nail T. Alternatively, in this embodiment, a table containing correction factors in correlation with curvatures of five levels based on curvatures of the nail T, i.e., different tilts of the surface of the nail T to the horizontal direction, at positions in the end regions of the nail T at predetermined intervals in the horizontal direction is stored in the correction-data memory area  824 , as illustrated in  FIG. 4A . The nail-information detecting process executed by the processor  81  determines one of the curvatures that is closest to the actual curvature of the nail T and classify it into the curvatures “1” to “5.” 
     Curvatures “1” to “5” are defined as illustrated in  FIG. 4B , where the curvature “1” corresponds to an overall flat surface of the nail T having a relatively small curvature, the curvature “5” corresponds to a curved surface of the nail T having a relatively large curvature, and the curvature “3” corresponds to the surface of a typical nail T having an intermediate curvature. Correction factors “1” to “4” are determined as illustrated in  FIG. 4A  for each curvature from one end to the other end of the nail along the width direction of the nail. The columns of the table in  FIG. 4A  correspond to positions D 1  to D 17  at the predetermined intervals at the end regions of the nail T, as illustrated in  FIG. 4B . 
       FIG. 4B  illustrates example curvatures within an area from the right end region in the width direction of the nail T corresponding to the respective curvatures.  FIG. 4A  illustrates the correction factors for the positions having respective curvatures, substantially aligned with the positions illustrated in  FIG. 4B . 
     The values “1” to “4” in  FIG. 4A  respectively correspond to the correction factors “1” to “4” in  FIG. 5  described below. 
     The drawing-data generating process executed by the processor  81  generates data required for printing a nail design on the nail T of the target finger U 1  by the drawing head  41 . 
     In this embodiment, the drawing-data generating process generates wide image data by expanding the design data of the nail design to be printed on the nail T in the width direction of the nail T in accordance with the curvature determined in the nail-information detecting process. 
     The image data for drawing is generated through the shape correction of the wide image data by compressing a portion of the data corresponding to the two end regions of the nail in the width direction in accordance with the curvature and matching the compressed data to the two-dimensional shape of the nail T. 
     The shape correction of the design data under the drawing-data generating process executed by the processor  81  will now be explained in detail with reference to  FIGS. 5 and 6 . In  FIGS. 5 and 6 , the intervals between the positions corresponding to respective correction factors in the end regions of the target nail T are increased compared to those in  FIGS. 4A and 4B  to simplify the curved shape of the nail into positions d 0  to d 6 , although  FIGS. 5 and 6  actually apply to a curved nail having a curved shape approximating the curvature “3” in  FIGS. 4A and 4B . 
       FIG. 5  illustrates an example table illustrating the correspondence between the positions d 0  to d 6  in an end region of the nail T and the correction factors at the respective positions. 
     The positions d 0  to d 6  in  FIG. 5  are the same as the positions d 0  to d 6  in  FIGS. 3 and 6 . In specific, the positions d 1  to d 6  correspond to both areas “Ar_L” and “Ar_R” that require curved surface correction, where the position d 6  corresponds to the outermost positions in the left and right end regions in the width direction of the nail having the largest curvature, and the position d 1  corresponds to the innermost positions in the areas “Ar_L” and “Ar_R,” closest to the area “Ar_N.” The position d 0  corresponds to the area “Ar_N” that requires no curved surface correction. 
     In the table in  FIG. 5 , the correction factor “1” in correlation with the position d 0  indicates no curved surface correction, whereas the positions d 1  to d 6  in correlation with the corrections factors “2” to “4,” respectively, indicate double to quadruple levels of correction. 
     In the areas “Ar_L” and “Ar_R” illustrated in  FIGS. 5 and 6 , the outermost position d 6  corresponds to a correction factor “4,” the positions d 4  and d 5  correspond to a correction factor “3,” and the positions d 1  to d 3  correspond to a correction factor “2.” The position d 0  in the area “Ar_N” that requires no curved surface correction corresponds to a correction factor “1” indicating no curved surface correction. 
     The drawing-data generating process executed by the processor  81  acquires the curvatures of the surface of the nail T, retrieves and refers to a table as illustrated in  FIG. 5  from the correction-data memory area  824  to assign correction factors corresponding to the curvatures to the design data on the nail design, to generate wide image data illustrated at the top of  FIG. 6 . 
     The wide image data is generated by expanding the design data by one time at the positions corresponding to the correction factor “1” and by four times at the positions corresponding to the correction factor “4” in the width direction of the nail T. 
     The drawing-data generating process executed by the processor  81  generates image data for drawing from the wide image data in reference to the table referred to in generating the wide image data (i.e., the table illustrated in  FIG. 5  in this embodiment). 
     In detail, the data of the outermost regions in the width direction of the nail corresponding to the correction factor “4” is decimated to one fourth in size, data corresponding to the correction factor “3” is decimated to one third in size, and data corresponding to the correction factor “2” is decimated to one second in size. The removed data items are indicated by white circles in the second row from the top of  FIG. 6 . 
     The data on the pattern to be drawn is allocated on the surface of the target nail T after appropriate decimation in accordance with the correction factors, to generate shape-corrected image data for drawing that is compressed in accordance with the curvatures at the two end regions of the nail in the width direction, as illustrated in the third row from the top in  FIG. 6 , and matched to the two-dimensional shape, i.e., the shape of the top plan view of the nail T as illustrated in bottom region of  FIG. 3 . 
     In this way, the design data can be subjected to shape correction suitable for the curvature of the nail T to achieve uniform print on the entire surface of the nail T including the two end regions, as illustrated in the bottom row in  FIG. 6 . 
     Unfortunately, in the state illustrated in the bottom row in  FIG. 6 , the density of the ink dots printed on the two end regions of the nail T is low compared to those in the central region of the nail T and causes a reduction in the printing density. 
     The drawing-data generating process executed by the processor  81  generates jet control data corresponding to the image data for drawing, where the jet control data determines the driving state of the nozzles during a plurality of scanning operations of the drawing head  41  on the basis of the curvatures. 
       FIG. 7A  illustrates a unit region consisting of 256×256 mask patterns. Print of such a unit region through four scanning operations will now be explained. Dot data items 0 to 255 respectively having values of 0 to 255 are uniformly dispersed across the unit region consisting of the mask patterns. For example, in order to print the unit region in four scanning operations in the drawing-data generating process, the dot data items 0 to 255 are categorized into four groups corresponding to the dot data items 0 to 63, 64 to 127, 128 to 191, and 192 to 255, respectively, and data determining the driving state of the nozzles during the scanning operations (i.e., which positions are to be targets of ink jet during the scanning operations) is generated in accordance with the correction factors illustrated in  FIG. 5 . 
       FIG. 7B  illustrates correction factors and jet control data in correlation with the driving state of the nozzles corresponding to the correction factors. 
       FIGS. 8A to 8D  are schematic views of the nozzles to be driven in the first to fourth scanning operations for the correction factors “1” to “4” during a drawing operation in accordance with the jet control data illustrated in  FIG. 7B . 
     For the correction factor “1” with no curved surface correction, the nozzles of the drawing head  41  are driven to jet ink to sequentially form the dots corresponding to each of the four categories during each of the first to fourth scanning operations, respectively, as illustrated in  FIGS. 7B and 8A . 
     In detail, the first scanning operation drives the nozzles of the drawing head  41  to jet ink onto areas corresponding to the dot data items 0 to 63 among the dot data items 0 to 255. The second scanning operation filters the dot data items 0 to 63 that have already been printed and drives the nozzles of the drawing head  41  to jet ink onto areas corresponding to the dot data items 64 to 127. The third scanning operation filters the dot data items 0 to 127 that have already been printed and drives the nozzles of the drawing head  41  to jet ink onto areas corresponding to the dot data items 128 to 191. The fourth scanning operation filters the dot data items 0 to 191 that have already been printed and drives the nozzles of the drawing head  41  to jet ink onto areas corresponding to the dot data items 192 to 255. After the four scanning operations, ink is jetted to form all the dot data items 0 to 255, to achieve a density of 100%. 
     The four scanning operation completes print of all the mask patterns corresponding to the dot data items 0 to 255. In other words, ink is jetted one time from each nozzle of the drawing head  41  to each of the dots 0 to 255 in a unit region. The single drawing of the full region (100% density) is thereby achieved. 
     For the correction factor “2,” ink is jetted once from each nozzle to form all the dots 0 to 255 by the first and second scanning operations of the drawing head  41 , and further jetted once from each nozzle to form all the dots 0 to 255 by the third and fourth scanning operations of the drawing head  41 . Thus, four scanning operations of the drawing head  41  jet ink two times from each nozzle to form the dots 0 to 255. The double drawing of the full region (200% density) is thereby achieved (see  FIG. 88 ). 
     For the correction factor “3,” ink is jetted once from each nozzle to form all the dots 0 to 255 by the first and second scanning operations of the drawing head  41 , and further jetted once from each nozzle to form all the dots 0 to 255 by each of the third and fourth scanning operations of the drawing head  41 . Thus, four scanning operations of the drawing head  41  jet ink three times from each nozzle to form the dots 0 to 255. The triple drawing of the full region (300% density) is thereby achieved (see  FIG. 8C ). 
     For the correction factor “4,” ink is jetted once from each nozzle to form all the dots 0 to 255 by each of the first to fourth scanning operations of the drawing head  41 . Thus, four scanning operations of the drawing head  41  jet ink four times from each nozzle to form the dots 0 to 255. The quadruple drawing of the full region (400% density) is thereby achieved (see  FIG. 8D ). 
     In this way, ink is jetted once from each nozzle onto the area “Ar_N,” which requires no curved surface correction and has a correction factor “1,” at a density of 100%, to uniformly apply an appropriate amount of ink on the nail T, as schematically illustrated in  FIG. 9 . 
     In contrast, ink is jetted four times from each nozzle onto the end regions of the nail T in the width direction having a correction factor “4,” to achieve a sufficient density of 400%. 
     Ink is jetted two times and three times, respectively, in the areas having correction factors “2” and “3,” to achieve densities of 200% and 300%. In this way, the density can be corrected in accordance with the curvatures. 
     Any jet control data generated in the drawing-data generating process other than that illustrated in  FIG. 7B  may also be used. 
     For example, in the case where the correction factor is “1” as illustrated in  FIGS. 7A and 8A , one fourth of the dots may be printed during each scanning operation, and then different nozzles, i.e., another portion of the nozzles may be driven during each scanning operation to print another fourth of the dots. 
     For example, the first scanning operation prints the dots 0 to 63 and a portion of the dots 64 to 127, as illustrated in  FIG. 10 . Similarly, the jet control data is generated so as to control the nozzles to print the dots 64 to 127 and a portion of the dots 128 to 191 in the second scanning operation, the dots 128 to 191 and a portion of the dots 192 to 255 in the third scanning operation, and the dots 192 to 255 and a portion of the dots 0 to 63 in the fourth scanning operation. 
     The number of nozzles to be driven is gradually increased to linearly control the density between 100% and 200%. 
     In this way, the density can be linearly controlled between 200% and 300% for the areas having a correction factor “2,” and between 300% and 400% for the areas having a correction factor “3”. 
     The drawing control process executed by the processor  81  controls the drawing head  41  to scan the unit region on the target nail a plurality of times while driving all or a portion of the nozzles, and forms a pattern through multipass printing. In this embodiment, the drawing head  41  is reciprocated on the nail T four times over each unit region, to form a pattern. 
     The processor  81  executing the drawing control process sends a control signal to the drawing unit  40  based on the jet control data of the drawing data generated in the drawing-data generating process executed by the processor  81 , and controls the X-direction shift motor  46 , the Y-direction shift motor  48 , and the drawing head  41  of the drawing unit  40  to print a pattern on the nail T in accordance with the drawing data. 
     In this embodiment, the nozzles to be driven are determined on the basis of the jet control data, and thus the drawing control process controls the driving of the nozzles of the drawing head  41  on the basis of the jet control data. 
     The display controlling process executed by the processor  81  controls the display  26  to present various menus on the display  26 . In this embodiment, the display controlling process causes the display  26  to present, for example, a selection menu of nail designs, thumbnail images for confirming designs, nail images of a target finger U 1 , various instructions, and other menus. 
     The curvature determined for the surface of the nail T of the user may appear on the display  26 , so that the user can confirm the curvature. If the user determines the curvature automatically selected by the apparatus to be inappropriate for her nail T, the curvature may be varied or finely adjusted by operating the operating unit  25  and/or the touch panel. 
     A method of drawing a pattern with the nail printer  1  according to this embodiment will now be explained with reference to  FIG. 11 . 
     To draw a pattern with the nail printer  1 , the user turns on the power and starts the controller  80 . 
     In response to an input operation of a drawing switch, the processor  81  starts the imaging control process to control the image capturing unit  50  to capture an image of the target finger U 1  with the image capturing device  51  while illuminating the target finger U 1  with the lighting devices  52 , before the drawing operation. In this way, the processor  81  acquires a nail image of the nail T of the target finger U 1  (step S 1 ). 
     The nail-information detecting process executed by the processor  81  acquires nail information including the outline of the nail T and the positions of the nail T in the height direction from the nail image (step S 2 ). 
     The processor  81  then acquires the curvatures indicating the curvature of the target nail T in the width direction from the nail information (step S 3 ). 
     After acquisition of the curvatures of the nail T, the processor  81  executes the drawing-image generating process to generate wide image data based on correction factors determined in accordance with the curvatures (step S 4 ). 
     In detail, the processor  81  generates wide image data corresponding to a width larger than the width of the apparent width of the top view of the nail T, in reference to a table containing correction factors for different positions on the nail T in the width direction corresponding to the curvatures. 
     The processor  81  carries out shape correction by compressing the portion of the wide image data corresponding to the two end regions of the nail T in the width direction in accordance with the curvatures in reference to the table used in the generation of wide image data, and matching the compressed data to the two-dimensional shape of the nail, to generate image data for drawing (step S 5 ). 
     The processor  81  generates jet control data corresponding to the image data for drawing to be used for control of the driving of the nozzles of the drawing head  41  on the basis of the correction factors corresponding to the curvatures (step S 6 ). 
     The drawing-data generating process executed by the processor  81  generates the jet control data corresponding to the image data for drawing. In response, the drawing control process executed by the processor  81  controls the operation of the drawing head  41  on the basis of the jet control data and starts printing the nail design on the nail T (step S 7 ). 
     In this embodiment, the printing of a unit region is completed after the drawing head  41  scans four times over the nail T. The nozzles to be driven and the positions on which ink is to be jetted during each scanning operation are controlled in accordance with the jet control data. 
     In the case where the surface of the target nail T consists of two or more unit regions, the same process as described above is repeated for each unit region. 
     The drawing control process executed by the processor  81  checks for the completion of the entire drawing process involving the nail T (step S 8 ). If the drawing process is completed (“YES” in step S 8 ), the drawing control process ends. If the drawing process is not completed (i.e., the four scanning operations of the drawing head is not completed or at least one imprinted unit region remain in multiple unit regions) (“NO” in step S 8 ), the process returns to step S 7 . 
     According to the embodiment described above, a nail printer  1 , which includes an inkjet drawing head  41  including multiple nozzles jetting ink and carrying out multipass printing of a pattern, acquires curvatures indicating the curvature of a nail T in the width direction, establishes jet control data for controlling the driving state of the nozzles during a plurality of scanning operations of the drawing head  41  on the basis of the curvatures of the surface of the nail T, and controls the drawing head  41  on the basis of the jet control data. 
     In this embodiment, the density of the printed pattern is adjusted through control of the jet of ink from the nozzles during a plurality of scanning operations. Thus, the image data of the nail design is relatively small, for example, 600 dpi. Thus, the memory storing the image (the nail-design memory area  823  in this embodiment) may have a small capacity. 
     The correction factors for the adjustment of the density of the pattern correspond to the curvatures of the surface of the nail T. Thus, the shape of the curved surface of the nail T can be subjected to appropriate curved surface correction, to achieve a beautiful finish on the entire nail T including the two end regions. 
     The drawing-data generating process generates wide image data by once expanding the length of the design data on the nail design to be printed on the nail T in the width direction in accordance with the curvatures and carries out shape correction by compressing the portion of the wide image data corresponding to the two end regions in the width direction in accordance with the curvatures and matching the compressed data to the two-dimensional shape of the nail T, to generate image data for drawing. 
     Shape correction for matching the image data of the nail design to the curvature of the nail prevents distortion and stretching of the design even in the two end regions of the nail in the width direction. Thus, a nail design can be drawn with a beautiful finish. 
     The above embodiments should not be construed to limit the present invention and may be appropriately modified within the gist of the present invention. 
     In the embodiment described above, the drawing-data generating process executed by the processor  81  carries out the curved surface correction including shape correction and density correction on the data of the nail design. The shape correction may be omitted. For example, in the case where the nail design includes a gradation of a plurality of colors or consists of only lines, the finish of the drawing is not greatly affected by slight distortion and/or stretching of the pattern in the end regions of the nail in the width direction. Thus, the data of such a nail design requires only density correction without shape correction. 
     In such a case, the drawing-data generating process generates jet control data corresponding to the image data for drawing in accordance with the correction factors corresponding to the curvatures and controls the jet of the nozzles of the drawing head  41  on the basis of the jet control data. This reduces the size of the image data on the nail design, while achieving a gradation of densities of 100% or higher in the two end regions of the nail in the width direction, through nozzle control. 
     In the embodiment described above, the image data on the nail design is stored in the memory  82 . Alternatively, the image data on the nail design may be retrieved from, for example, an external unit via the Internet. 
     In such a case, image data having a large volume requires long transmission time. In the embodiment described above, the image data on the nail design has a relatively small volume of, for example, 600 dpi, because the jet ink from nozzles during a plurality of scanning operations is controlled to adjust the density of the drawn pattern. Thus, data can be smoothly transmitted and received even when the image data on the nail design is to be retrieved from an external unit. 
     In the embodiment described above, the drawing head  41  is of an inkjet type. Alternatively, the nail printer may include an inkjet drawing head and a drawing tool, such as a pen, both of which may be used for drawing. 
     The embodiments described above should not be construed to limit the present invention, and the claims and other equivalents thereof are included in the scope of the invention.