Patent Publication Number: US-9892524-B2

Title: Image displaying methods, devices, and storage media

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior Chinese Patent Application No. 201510424387.8, filed on Jul. 17, 2015, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to the technical field of communications and, more particularly, to image processing and displaying. 
     BACKGROUND 
     LCD panels may be based on liquid crystals operating in various different modes and alignment. LCD screens may be classified into hard screens and soft screens. Soft screens, which mainly refer to panels based on vertical alignment (VA) type liquid crystals, are characterized in that, when a soft screen is touched by a finger, a water ripple effect may appear on the soft screen. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
     According to one embodiment of the present disclosure, a method is provided, comprising: acquiring an image upon receipt of a request for displaying the image; locating in the image an image region composed of at least three continuously adjoining monochromatic sections, wherein each of the monochromatic sections comprises four or more continuous pixels; when a difference in color value between any two adjacent sections of the adjoining monochromatic sections in the image region is less than a threshold value, calculating one or more target color values based on color values of the monochromatic sections in the image region; replacing color values of the image region in the image with the one or more target color values to generate a target image; and displaying the target image, storing the target image. 
     In another embodiment, a method is disclosed comprising: acquiring an image upon receipt of a request for displaying the image on a display device; determining whether the display device is a soft screen; displaying the image in the display device when the display device is not a soft screen; and when the display device is a soft screen, locating in the image an image region composed of at least three continuously adjoining monochromatic sections wherein each of the monochromatic sections comprises four or more continuous pixels; when a difference in color value between any two adjacent sections of the adjoining monochromatic sections in the image region is less than a threshold value, calculating one or more target color values based on color values of the monochromatic sections in the image region; replacing color values of the image region in the image with the one or more target color values to generate a target image; and displaying the target image in the display device. 
     In another embodiment, a device is disclosed comprising: a memory having codes stored therein; and one or more processors, when executing the codes, configured to: acquire an image upon receipt of a request for displaying the image; locate in the image an image region composed of at least three continuously adjoining monochromatic sections wherein each of the monochromatic sections comprises four or more continuous pixels; when a difference in color value between any two adjacent sections of the adjoining monochromatic sections in the image region is less than a threshold value, calculate one or more target color values based on color values of the monochromatic sections in the image region; replace color values of the image region in the image with the one or more target color values to generate a target image; and display the target image. 
     In another embodiment, a device is disclosed comprising: a memory having codes stored therein; and one or more processors, when executing the codes, configured to: acquire an image upon receipt of a request for displaying the image on a display device; determine whether the display device is a soft screen; display the image in the display device when the display device is not a soft screen; and when the display device is a soft screen, locate in the image an image region composed of at least three continuously adjoining monochromatic sections wherein each of the monochromatic sections comprises four or more continuous pixels; when a difference in color value between any two adjacent sections of the adjoining monochromatic sections in the image region is less than a threshold value, calculating one or more target color values based on color values of the monochromatic sections in the image region; replace color values of the image region in the image with the one or more target color values to generate a target image; and display the target image in the display device. 
     In yet another embodiment, non-transitory computer-readable storage medium comprising instructions stored therein that, when executed by a processor of a computing device, causes the computing device to: acquire an image upon receipt of a request for displaying the image; locate in the image an image region composed of at least three continuously adjoining monochromatic sections; when a difference in color value between any two adjacent sections of the adjoining monochromatic sections in the image region is less than a threshold value, calculate one or more target color values based on color values of the monochromatic sections in the image region; replace color values of the image region in the image with the one or more target color values to generate a target image; and display the target image. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The devices, systems and methods of this disclosure may be better understood with reference to the following drawings and description. Non-limiting and non-exhaustive embodiments are described with reference to the following drawings. The components in the drawings are not necessarily to scale. Emphasis instead is placed upon illustrating the principles of the invention. In the drawings, like referenced numerals designate corresponding parts throughout the different views. 
         FIG. 1( a )  is a flowchart showing an image displaying method according to an exemplary embodiment. 
         FIG. 1( b )  illustrates an image containing an image region having a plurality of adjoining monochromatic sections. 
         FIG. 2  is a flowchart showing another image displaying method according to an exemplary embodiment. 
         FIG. 3  is a flowchart showing a further image displaying method according to an exemplary embodiment. 
         FIG. 4  is a flowchart showing a further image displaying method according to an exemplary embodiment. 
         FIG. 5  is a schematic block diagram showing an image displaying device according to an exemplary embodiment. 
         FIG. 6  is a schematic block diagram showing another image displaying device according to an exemplary embodiment. 
         FIG. 7  is a schematic block diagram showing a further image displaying device according to an exemplary embodiment. 
         FIG. 8  is a schematic block diagram showing a further image displaying device according to an exemplary embodiment. 
         FIG. 9  is a schematic block diagram showing a further image displaying device according to an exemplary embodiment. 
         FIG. 10  is a schematic block diagram showing a further image displaying device according to an exemplary embodiment. 
         FIG. 11  is a block diagram showing an image displaying device according to an exemplary embodiment. 
         FIG. 12  illustrates a display device having an LCD panel and a touch screen. 
     
    
    
     DETAILED DESCRIPTION 
     Reference throughout this specification to “one embodiment,” “an embodiment,” “exemplary embodiment,” or the like in the singular or plural means that one or more particular features, structures, or characteristics described in connection with an embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment,” “in an exemplary embodiment,” or the like in the singular or plural in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics in one or more embodiments may be combined in any suitable manner. 
     The terminology used in the description of the disclosure herein is for the purpose of describing particular examples only and is not intended to be limiting of the disclosure. As used in the description of the disclosure and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “may include,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and/or groups thereof. 
     The methods, devices, and modules described herein may be implemented in many different ways and as hardware, firmware, software or in different combinations of hardware, firmware, and software. For example, all or parts of the implementations may be a processing circuitry that includes an instruction processor, such as a central processing unit (CPU), microcontroller, a microprocessor; or application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), controllers, micro-controllers, microprocessors, other electronic components; or as circuitry that includes discrete logic or other circuit components, including analog circuit components, digital circuit components or both; or any combination thereof. The circuitry may include discrete interconnected hardware components or may be combined on a single integrated circuit die, distributed among multiple integrated circuit dies, or implemented in a Multiple Chip Module (MCM) of multiple integrated circuit dies in a common package, as examples. 
     Subject matter will now be described in more detail hereinafter with reference to the accompanying drawings. The drawings form a part hereof, and show, by way of illustration, specific exemplary embodiments. Subject matter may, however, be embodied in a variety of different forms and, therefore, covered or claimed subject matter is intended to be construed as not being limited to any exemplary embodiments set forth herein. A reasonably broad scope for claimed or covered subject matter is intended. Among other things, for example, subject matter may be embodied as methods, devices, components, or systems. The following detailed description is, therefore, not intended to be taken in a limiting sense. In the following description, when the accompanying drawings are referred to, like numbers in different drawings represent like elements unless otherwise specified. 
     In order to overcome problems with the related technology, the disclosure provides image displaying methods, devices and computer readable storage media, whereby color banding and artificial abrupt change of color may be prevented or reduced when a soft screen is used to display regions of similar colors in an image. 
       FIG. 1( a )  is a flowchart showing an image displaying method according to an exemplary embodiment of this disclosure. The image displaying method as shown in  FIG. 1( a )  may be implemented in smart devices, such as mobile phones, computers, digital broadcast terminals, messaging devices, game consoles, tablets, medical equipment, fitness equipment, and personal digital assistants. The image displaying method according to this disclosed embodiment may prevent color banding when a soft screen in a smart device displays regions of similar and continuously varying colors in an image. 
     In step S 11 , an image is acquired by the smart device upon receipt of an instruction for displaying the image. Specifically, the smart device may be used to render still images or video frames. An image or video frame, referred to as an image hereinafter, may be delivered from any communications networks connected to the smart device or may be preloaded into the storage of the smart device. The smart device may be instructed or receive a request from a user to display an image or play a video when the user of the device runs an image or video rendering application on the smart device. Upon receipt of the instruction or request for displaying the designated image, the smart device may read from its storage or download from the communications network the designated image. The storage of the smart device may be of any physical form, such as hard disk, flash memory, and optical disk. Those of ordinary skill in the art understand that an image may be composed of a plurality of pixels each having a color value and may be stored or delivered from the communications network in compressed form. Accordingly, the smart device may decompress the image prior to gaining access to the color values of the pixels. 
     In step S 12 , an image region composed of at least three continuously adjoining monochromatic sections in the designated image is determined by the smart device. To be continuously adjoining, the monochromatic sections forms one continuous and unbroken image region. Each monochromatic section is adjacent to at least one other monochromatic section but is not necessarily adjacent to two or more monochromatic sections. Here, a monochromatic section is composed of a plurality of adjoining pixels having the same color value. The color value can be expressed in RGB system well known in the art. For example, the monochromatic section may be composed of 6 pixels arranged in 2 lines and 3 columns and the 6 pixels in the 2 lines and 3 columns are all pure red, i.e., the RGB value of each of these 6 pixels is RGB (255, 0, 0). It is assumed in the embodiments of this disclosure that color values are in the resolution of 8 bit. However, in some other embodiments, the RGB color space may have resolution higher than 8 bit. Each RGB value set represents one unique color. A group of colors may be referred to under the same name but are still considered distinctive colors. For example, RGB value sets (255, 0, 0), (200, 0, 0) and (100, 0, 0) may all be referred to as pure red with distinctive brightness. But under the RGB system and in accordance with this disclosure, they are three distinctive colors. Those of ordinary skill in the art understand that RGB system may be derived from various known or unknown tri-colorimetric basis, such as sRGB, Adobe RGB, Adobe wide gamut RGB, and scRGB. The tri-colorimetric values may be on liner scale or may be gamma-corrected, as is well known in the art. In addition, RGB is merely an exemplary color descriptive system according to the principles of colorimetry. The present embodiment and other embodiments disclosed in this specification are equally applicable to other color description systems, such as color description system based on luma and chroma, such as YCrCb and YPbPr, 
     The image region determined in step S 12  is preferably composed of at least three adjoining monochromatic sections and each monochromatic section includes a plurality of adjoining pixels. This is illustrated in  FIG. 1( b ) , which shows an image to be displayed. The image contains an array of pixels.  FIG. 1( b )  show an array of 400 pixels. However, an image and the corresponding display screen may contains any other suitable number of pixels. As an example, the image region A may include 6 adjoining monochromatic sections A 1 -A 6 . The first monochromatic section A 1  may be composed of 6 pixels in 2 lines and 3 columns, and the 6 pixels in 2 lines and 3 columns are all pure red with almost full brightness, i.e., the color value of these 6 pixels in RGB is (250, 0, 0). The second monochromatic section A 2  may be composed of 4 pixels in 2 lines and 2 columns, and the 4 pixels in 2 lines and 2 columns may be all pure red but with less brightness, e.g., the color value of the 4 pixels in RGB may be (240, 0, 0). The third monochromatic section A 3  may be composed of 4 pixels in 2 lines and 2 columns, and the 4 pixels in 2 lines and 2 columns may also be pure red but even less bright, e.g., the color value of the 4 pixels may be RGB (230, 0, 0). The fourth monochromatic section A 4  may be composed of 6 pixels in 2 lines and 3 columns and the 6 pixels in 2 lines and 3 columns may be all pure red but less bright than the third monochromatic section, e.g., the color value of the 6 pixels in RGB may be (220, 0, 0). The fifth monochromatic section A 5  may be composed of 6 pixels in 3 lines and 2 columns and the 6 pixels in 3 lines and 2 columns may be all pure red but less bright than the fourth monochromatic section, e.g., the color value of the 6 pixels in RGB may be (210, 0, 0). The sixth monochromatic section A 6  may be composed of 8 pixels in 2 lines and 4 columns and the 8 pixels in 2 lines and 4 columns may be all pure red but less bright than the fifth monochromatic section, e.g., the color value of the 8 pixels in RGB may be (200, 0, 0). Thus, the image region A is composed of the above 6 adjoining monochromatic sections and includes a total of 34 pixels. Each monochromatic section contains a plurality of adjoining pixels. Pixels are adjoining if they cover a continuous and unbroken area. The monochromatic sections A 1 -A 6  are rectangular in shape in the example above but may be in irregular shape. These regions each have different colors but these colors may be similar and may be intended to show a smooth and continuous transition of various shade of red from monochromatic section  1  to monochromatic section  6 . Those of ordinary skill in the art understand that similar colors are not limited to the slightly different shade of red in the example above. Any colors that are sufficiently close in any one or combination of the three RGB components may be considered identical in color. For example, (100, 40, 80) may be considered similar color to (110, 40, 80), or (100, 44, 80), or (102, 38, 82). 
     After the smart device finds at least one image region composed of at least three adjoining monochromatic sections in the designated image, it acquires color values for the respective monochromatic sections in the at least one image region. For example, it is assumed that the image region A located by the smart device in the image includes the 4 adjoining monochromatic sections described above. The smart device acquires color value of the first, second, third, and fourth monochromatic sections and respectively obtains RGB values of (250, 0, 0), (240, 0, 0), (230, 0, 0), and (220, 0, 0). 
     In step S 13 , when a difference in color value between any two adjacent ones of the adjoining monochromatic sections in the image region is less than a threshold value, a target color value is determined and calculated in accordance with a predetermined scheme by using color values of the monochromatic sections in the image region. The determination and calculation of the target value may be triggered under more rigid conditions. For example, target color value may be calculated only when differences between all adjacent sections of the monochromatic sections are less than a predetermined threshold. Here, the threshold may be a predetermined color difference value. For example, the threshold value may be preset to RGB difference of (15, 15, 15). The difference between RGB values of the adjoining monochromatic sections represents the degree of similarity of the colors of the regions. The smaller the value, the closer the colors. When the colors between two adjoining monochromatic sections become closer than the threshold, a soft panel, by its physical characteristics and response, may display the two colors visually identically even though the panel is driven physically with parameters intended to display two different colors. Thus, a soft panel may display monochromatic sections  1  and  2  of the exemplary embodiment above in the same visual color, and display monochromatic sections  3  and  4  in one different color. The two displayed colors may be visually different and non-continuous. They thus may appear visually as two bands of red with an abrupt boundary. The soft panel thus may distort the intended smooth color transition from the monochromatic section  1  to  4 . By replacing the color values of these monochromatic sections with some target color values when the color difference from one monochromatic section to another adjacent section is less than the predetermined threshold, the smart device may enable the soft panel to display the image region without color banding described above. 
     For instance, it is assumed that the threshold value is preset to an RGB difference of (20, 20, 20). The smart device determines an image region A composed of 6 adjoining monochromatic sections in an image region of the image, as is shown in  FIG. 1( b ) . The RGB values of the first to sixth monochromatic sections A 1 -A 6  are respectively (250, 0, 0), (240, 0, 0), (230, 0, 0), (220, 0, 0), (210, 0, 0) and (200, 0, 0). Furthermore, the monochromatic sections A 1  through A 6  are adjoining in succession. The smart device may calculate a difference in color value between each two adjacent ones of adjoining monochromatic sections in the image region and determine whether the difference is less than a threshold value of RGB (20, 20, 20). Specifically, the smart device finds through the calculation that the difference in color value between each two adjacent monochromatic sections in the image region A of the designated image is equal to RGB (10, 0, 0), less than the threshold value RGB (20, 20, 20). This may indicate to the smart device that the adjoining monochromatic sections in the image region have similar color values and when the designated image is displayed on some soft screens, some monochromatic sections in the image region of the designated image may be displayed in the same color, causing color banding with sharp change of color and unsmooth color transition in the image region. 
     In step S 14 , the smart device may determine target color values for the monochromatic regions having similar colors in accordance with some predetermined scheme and replace the color values of the monochromatic sections in the image region with the target color values, thereby avoiding color banding and sharp change of color in the image region. 
     Various ways for determining and calculating the target color value using the color values of the monochromatic sections in the image region may be implemented in accordance with the embodiment above. In the following, two specific implementations are described. 
     In the first implementation, the smart device calculates an average value of the color values of the adjacent monochromatic sections in the image region having similar colors and then uses the calculated average value as the target color value for all the adjacent monochromatic sections. For example, it is assumed that the smart device determines that an image region A in the designated image is composed of 6 adjoining monochromatic sections, as is described previously and shown in  FIG. 1( b ) , i.e., the RGB values of the first monochromatic section A  1  to the sixth monochromatic section A 6  are respectively (250, 0, 0), (240, 0, 0), (230, 0, 0), (220, 0, 0), (210, 0, 0), and (200, 0, 0). The smart device calculates an average value of the color values of the  6  adjoining monochromatic sections in the image region A for each RGB component, which is [(250, 0, 0)+(240, 0, 0)+(230, 0, 0)+(220, 0, 0)+(210, 0, 0)+(200, 0, 0)]/6=(225, 0, 0). In accordance with the first implementation, the smart device set the average value RGB (225, 0, 0) as the target color value for the 6 adjacent monochromatic sections. 
     In the second implementation for determining the target color value for the monochromatic sections, the smart device may derive the target color value from a maximal color value and a minimal color value in the image region and a predetermined coefficient. Specifically, the maximal color value and the minimal color value of the adjoining monochromatic sections in the image region are determined by the smart device. The maximal or minimal color value may be determined by finding the maximum or minimum of each of the RGB component within the image region. For example, the R component of the maximal color value may be the maximum of the R values for all the monochromatic sections in the image region. The smart device then obtains a first color value by calculating the difference between the maximal color value and the minimal color value. The smart device then scale the first color value to obtain a second color value by multiplying the first color value with the predetermined coefficient. Finally, the smart device obtains the target color value by calculating the sum of the minimal color value and the second color value. 
     For example, the predetermined coefficient may be 0.6. It is assumed again that the smart device determines that an image region A in the image is composed of 6 adjoining monochromatic sections as shown in  FIG. 1( b )  and the RGB values of the first to sixth monochromatic sections A 1  to A 6  are (250, 0, 0), (240, 0, 0), (230, 0, 0), (220, 0, 0), (210, 0, 0), and (200, 0, 0), respectively. Then, the smart device determines that the maximal RGB color value is (250, 0, 0) and the minimal RGB color value is (200, 0, 0) in the image region. The smart device then determines that the difference between the maximal color value and the minimal color value of the adjacent monochromatic sections in the image region is (250, 0, 0)−(200, 0, 0)=(50, 0, 0). The smart device sets this difference value as the first color value. Next, a product of the first color value (50, 0, 0) and the predetermined coefficient 0.6 is calculated as the second color value: (50, 0, 0)×0.6=(30, 0, 0). Thereafter, a sum of the minimal color value (200, 0, 0) and the second color value (30, 0, 0) is calculated as the target color value: (200, 0, 0)+(30, 0, 0)=(230, 0, 0). 
     Those skilled in the art understand that the two implementations in determining the target color value of the adjacent monochromatic sections of an image region is for illustration purpose only. Many other implementations may be suitable and within the spirit of the current disclosure. In addition, while the above implementation aims at replacing all the adjacent monochromatic sections with the same target color value, the smart device may divide the monochromatic sections into groups and replace each group with a different target color value. The target values for the groups of monochromatic sections may be determined such that a soft screen may be capable of displaying them with smooth transitions and without color banding and sharp visual color boundaries. 
     In step S 14 , the smart device replaces the color values of the monochromatic sections of the image region in the designated image by the target color value or values to generate a target image. Other parts of the target image may be kept unaltered and the same as those of the original image. 
     In step S 15 , the target image is delivered to the screen and is displayed. Even if the display screen of the smart device may be a soft screen, color banding and sharp change of color may be prevented when the target image is displayed. 
     Thus, in the embodiment shown in  FIG. 1 , before an image is displayed, the smart device first determine and locate an image region composed of at least three monochromatic sections in the designated image in advance. Those of ordinary skill in the art understand that there may be a plurality of such image regions and the smart device may identify each of these image regions in the image under the same principle described above. For each of these image regions, the smart device may further determine whether the difference in color value between each two adjacent ones of the adjoining monochromatic sections in the image region is less than a predetermined threshold value. A difference color value that is smaller than the predetermined threshold indicates that the adjoining monochromatic sections in the image region have similar colors. In order to avoid color banding and sharp change of color rather than a smooth transition when the designated image is displayed by a soft screen, one or more target color values are determined by the smart device for replacing the color values of the adjacent monochromatic sections in the image region that have similar colors. A resulting target image is thus generated and displayed, thereby avoiding color banding and abrupt change of color. 
       FIG. 2  is a flowchart showing another image displaying method according to another exemplary embodiment. The image displaying method shown in  FIG. 2  may be implemented in smart devices, such as mobile phones, computers, digital broadcast terminals, messaging devices, game consoles, tablets, medical equipment, fitness equipment, and personal digital assistants. The embodiment shown in  FIG. 2  is a further variant of the embodiment shown in  FIG. 1( a ) . Steps S 21 -S 25  are identical to S 11 -S 15  of the embodiment of  FIG. 1  and the description and explanation above for  FIG. 1( a )  apply to the steps S 21 -S 25 . The method shown in  FIG. 2  further comprises the following steps for displaying an image that has been previously displayed. 
     In step S 26 , the target image determined by the smart device is stored in a storage medium for reuse after being displayed on the display screen. The smart device may store the target image in any storage medium including but not limited to magnetic disk, flash memory, and optical disk. The smart device may store the target image for various purposes. For example, when future need arises for redisplay of the same image, the smart device may acquire the target image from its storage without having to repeat the above steps S 21 -S 24 . 
     In step S 27 , a correspondence relation between the designated image and the target image is established and logged by the smart device. The correspondence relationship may be maintained in a lookup table containing pointers to a plurality of designated images and pointers to the corresponding plurality of target images. The lookup table or any other implementation may facilitate the smart device in displaying repeatedly requested images. 
     In step S 28 , upon receiving a request for displaying an image, the smart device determines whether the requested designated image corresponds to a target image already stored in the storage medium based on the correspondence relationship, e.g., the lookup table, between designated images and the corresponding target images. If such a corresponding image is found in the lookup table, then the corresponding target image is used as the target image for the current requested image. 
     In step S 29 , the target image is displayed by the smart device. 
       FIG. 3  is a flowchart showing a further image displaying method according to another exemplary embodiment. The image displaying method shown in  FIG. 3  is applicable to smart devices such as mobile phones, computers, digital broadcast terminals, messaging devices, game consoles, tablets, medical equipment, fitness equipment, and personal digital assistants. The embodiment shown in  FIG. 3  is a further variant of the embodiment shown in  FIG. 2 . Steps S 31 -S 37  are identical to S 21 -S 27  of the embodiment of  FIG. 2  and the description and explanation above apply to the steps S 31 -S 37 . The method shown in  FIG. 3  further comprises the following steps. 
     In step S 38 , upon receiving a request for deleting an image from, for example, the storage medium of the smart device, the smart device determines whether a target image corresponding to the image requested to be deleted was previously processed, displayed, and thus also stored in the storage medium of based on the lookup table between images and target images. Here, the receipt of the instruction or request for deleting an image indicates that the user does not need the image in the near future. Thus, the user does not need the target image either. The smart device therefore may delete the target image from its storage medium in addition to deleting the image as requested. 
     In step S 39 , the requested image and the target image are deleted from the storage medium of the smart device. 
       FIG. 4  is a flowchart showing another image displaying method according to another exemplary embodiment. The method shown in  FIG. 4  is applicable to smart devices such as mobile phones, computers, digital broadcast terminals, messaging devices, game consoles, tablets, medical equipment, fitness equipment, and personal digital assistants. The embodiment shown in  FIG. 4  is a variant of the embodiment shown in  FIG. 1( a ) . For steps that are identical to  FIG. 1( a ) , description and explanation of the embodiment shown in  FIG. 1( a )  apply. The method shown in  FIG. 4  comprises the following steps. 
     In Step S 41 , an image is acquired upon receipt of an instruction or request for displaying the designated image. This step is similar to S 11  of  FIG. 1( a ) . 
     In step S 42 , the smart device determines the type of screen for the display device for displaying the requested image. The display screen may be a build-in screen in the smart device. It may be an external display device connected to the smart device by wire or wireless connections well known in the art. As described previously, if the display screen is a soft screen, similar and non-identical colors in the image may be displayed as the same color, leading to potential color banding and unintended abrupt change of colors. On the contrary, a hard screen may not be faced with such a problem. 
     In step S 43 , the smart device determines whether the display device is a soft screen. When the display device is a soft screen, step S 45  is executed. When the display device for displaying the requested image is not a soft screen, step S 44  is executed. In step S 44 , the display device may be used to display the requested image without modification because hard screens may not be faced with color banding problem. In step S 45 -S 48 , however, the device follows the steps of S 12  to S 15  to process and display a corresponding target image on the soft screen rather than the originally requested image for preventing color banding and abrupt color changes in image regions where continuous and smooth color transition may be intended. 
       FIG. 5  is the schematic block diagram showing an image displaying device according to an exemplary embodiment for preventing color banding and abrupt change of color from occurring when a soft screen displays regions of similar colors in an image. Referring to  FIG. 5 , the device comprises an acquiring module  11 , a first determining module  12 , a second determining module  13 , a modifying module  14  and a first display module  15 . 
     The acquiring module  11  is configured to acquire an image upon receipt of an instruction or request for displaying the image. The first determining module  12  is configured to determine and identify whether an image region is composed of at least three adjoining monochromatic sections in the designated image. The second determining module  13  is configured to determine and calculate one or more target color values in accordance with a preset scheme based on color values of the monochromatic sections in the image region, when a difference in color value between each two adjacent ones of the adjoining monochromatic sections in the image region is less than a threshold value. The modifying module  14  is configured to replace color values of the image region in the requested image with the target color values so as to generate a target image. The first display module  15  is configured to display the target image. 
       FIG. 6  is a schematic block diagram showing another image displaying device according to an exemplary embodiment for preventing color banding and abrupt change of color from occurring when a soft screen displays regions of similar colors in an image. Referring to  FIG. 6 , the device comprises an acquiring module  21 , a first determining module  22 , a second determining module  23 , a modifying module  24 , a first display module  25 , a first storage module  26 , a first establishing module  27 , a third determining module  28  and a second display module  29 . 
     The acquiring module  21  is configured to acquire an image upon receipt of an instruction or request for displaying the image. The first determining module  22  is configured to determine and locate whether an image region is composed of at least three adjoining monochromatic sections in the requested image. The second determining module  23  is configured to determine and calculate one or more target color values in accordance with a preset scheme by using color values of the monochromatic section in the image region when a difference in color value between any two adjacent ones of the adjoining monochromatic sections in the image region is less than a threshold value. The modifying module  24  is configured to replace color values of the image region in the designated image with the one or more target color values so as to generate a target image. The first display module  25  is configured to display the target image. The first storage module  26  is configured to store the target image in a storage medium for reuse. The first establishing module  27  is configured to establish and log a correspondence relation between the designated image and the target image in an exemplary form of lookup table. Upon receipt of another instruction or request for redisplaying the designated image, the third determining module  28  is configured to determine whether the target image corresponding to the designated image is already stored in the storage medium based on the correspondence relation between designated images and target images. If the corresponding target image is found, the smart device may use it as target image rather than recalculating it. The second display module  29  is configured to display the target image of the requested image in the other instruction or request. 
       FIG. 7  is a schematic block diagram showing a further image displaying device according to another exemplary embodiment for preventing color banding and abrupt change of color from occurring when a soft screen displays regions of similar colors in an image. Referring to  FIG. 7 , the device comprises an acquiring module  31 , a first determining module  32 , a second determining module  33 , a modifying module  34 , a first display module  35 , a second storage module  36 , a second establishing module  37 , a fourth determining module  38 , and a deletion module  39 . 
     The acquiring module  31  is configured to acquire an image upon receipt of an instruction or request for displaying the designated image. The first determining module  32  is configured to determine and locate whether an image region is composed of at least three adjoining monochromatic sections in the image. The second determining module  33  is configured to determine and calculate one or more target color values in accordance with a preset scheme by using color values of the monochromatic sections in the image region when a difference in color value between any two adjacent ones of the adjoining monochromatic sections in the image region is less than a threshold value. The modifying module  34  is configured to replace color values of the image region in the designated image with the one or more target color values so as to generate a target image. The first display module  35  is configured to display the target image. The second storage module  36  is configured to store the target image in a storage medium. The second establishing module  37  is configured to establish and log a correspondence relation between the designated image and the target image in an exemplary form of lookup table. Upon receipt of an instruction or request to delete the designated image, the fourth determining module  38  is configured to determine whether the target image corresponding to the designated image is already stored in the storage medium based on the correspondence relation between designated images and target images in the lookup table. If the corresponding target image is found, then the deleting module  39  is configured to delete the target image in addition to the designated image as requested. 
       FIG. 8  is a schematic block diagram showing a further image displaying device according to another exemplary embodiment for preventing color banding and abrupt change of color from occurring when a soft screen displays regions of similar colors in an image. Referring to  FIG. 8 , the device comprises an acquiring module  41 , a first determining module  42 , a second determining module  43 , a modifying module  44 , a first display module  45 , a fifth determining module  46 , a judging module  47 , a triggering module  48  and a third display module  49 . 
     The acquiring module  41  is configured to acquire an image upon receipt of an instruction or request for displaying the image. The first determining module  42  is configured to determine and locate whether an image region is composed of at least three adjoining monochromatic sections in the requested image. The second determining module  43  is configured to determine and calculate one or more target color values in accordance with a preset scheme by using color values of the monochromatic sections in the image region when a difference in color value between any two adjacent ones of the adjoining monochromatic sections in the image region is less than a threshold value. The modifying module  44  is configured to replace color values of the image region in the requested image with the target color values so as to generate a target image. The first display module  45  is configured to display the target image. The fifth determining module  46  is configured to determine the type of a display device for displaying the requested image. The judging module  47  is configured to determine whether the display device for displaying the requested image is a soft screen. The triggering module  48  is configured to trigger the first determining module  42  when the display device for displaying the designated image is a soft screen. The third display module  49  is configured to display the image by using the display device when the display device for displaying the designated image is not a soft screen. 
       FIG. 9  is a schematic block diagram showing a further image displaying device according to another exemplary embodiment for preventing color banding and abrupt change of color from occurring when a soft screen displays regions of similar colors in an image. Referring to  FIG. 9 , the device comprises an acquiring module  51 , a first determining module  53 , a second determining module  52 , a modifying module  54 , and a first display module  55 . The second determining module  52  further includes a first calculation submodule  521  and a determining submodule  522 . 
     The acquiring module  51  is configured to acquire an image upon receipt of an instruction or request for displaying the image. The first determining module  53  is configured to determine whether an image region is composed of at least three adjoining monochromatic sections in the image. The second determining module  52  is configured to determine and calculate one or more target color values in accordance with a preset scheme by using color values of the monochromatic sections in the image region when a difference in color values between each two adjacent ones of the adjoining monochromatic sections in the image region is less than a threshold value. The first calculation submodule  521  is configured to calculate an average value of the color values of the monochromatic sections in the image region. The determining submodule  522  is configured to determine said average value as the target color value. The modifying module  54  is configured to replace color values of the image region of the requested image with the target color values so as to generate a target image. The first display module  55  is configured to display the target image. 
       FIG. 10  is a schematic block diagram showing a further image displaying device according to another exemplary embodiment for preventing color banding and abrupt change of color from occurring when a soft screen displays regions of similar colors in an image. Referring to  FIG. 10 , the device comprises an acquiring module  61 , a first determining module  63 , a second determining module  62 , a modifying module  64 , a first display module  65 . The second determining module  62  includes an acquiring submodule  621 , a second calculation submodule  622 , a third calculation submodule  623  and a fourth calculation submodule  624 . 
     The acquiring module  61  is configured to acquire an image upon receipt of an instruction or request for displaying the image. The first determining module  63  is configured to determine whether an image region is composed of at least three adjoining monochromatic sections in the requested image. The second determining module  62  is configured to determine and calculate one or more target color values in accordance with a preset scheme by using color values of the monochromatic sections in the image region when a difference in color value between each two adjacent ones of the adjoining monochromatic sections in the image region is less than a threshold value. The acquiring submodule  621  is configured to acquire a maximal color value and a minimal color value in the image region. The second calculation submodule  622  is configured to calculate a difference between the maximal color value and the minimal color value in the image region as a first color value. The third calculation submodule  623  is configured to calculate a product of the first color value and a predetermined coefficient as a second color value. The fourth calculation submodule  624  is configured to calculate a sum of the minimal color value and the second color value as the target color value. The modifying module  64  is configured to replace color values of the image region in the designated image with the target color value so as to generate a target image. The first display module  65  is configured to display the target image. 
     Specific operations performed by the modules in the above device embodiments have been described in detail in corresponding method embodiments. Detailed description is omitted here and can be found in previous method embodiments. 
       FIG. 11  is a block diagram showing an image displaying device  800  according to an exemplary embodiment. The device  800  may be a smart device including but not limited to a mobile phone, a computer, a digital broadcast terminal, a messaging device, a game console, a tablet, a medical equipment, a fitness equipment, and a personal digital assistant. 
     Referring to  FIG. 11 , the device  800  may include one or more of the following components: a processing component  802 , a memory  804 , a power component  806 , a multimedia component  808 , an audio component  810 , an input/output (I/O) interface  812 , a sensor component  814  and a communication component  816 . 
     The processing component  802  preferably controls the overall operations of the device  800 , such as the operations associated with display, telephone calls, data communications, camera operations, and recording operations. The processing component  802  may include one or more processors  820  for executing instructions to perform all or part of the steps in the above described methods. Moreover, the processing component  802  may include one or more modules which facilitate the interaction between the processing component  802  and other components. For instance, the processing component  802  may include a multimedia module to facilitate the interaction between the multimedia component  808  and the processing component  802 . 
     The memory  804  is configured to store various types of data to support the operation of the device  800 . Examples of such data include instructions for any applications or operating system operated on the device  800 , and data such as contact data, phonebook data, messages, images, and video. The memory  804  may be implemented using any type of volatile or non-volatile memory devices, or a combination thereof, such as a static random access memory (SRAM), an electrically erasable programmable read-only memory (EEPROM), an erasable programmable read-only memory (EPROM), a programmable read-only memory (PROM), a read-only memory (ROM), a magnetic memory, a flash memory, a magnetic or optical disk. 
     The power component  806  supplies power to various components of the device  800 . The power component  806  may include a power management system, one or more power sources, and any other components associated with the generation, management, and distribution of power in the device  800 . 
     The multimedia component  808  includes a screen providing an output interface between the device  800  and the user. In some embodiments, the screen may include a liquid crystal display (LCD) and a touch panel (TP).  FIG. 12  shows an example of a soft LCD display. The display  900  includes an LCD panel  902  comprising an array of individually addressable pixels  904 . The array of pixels is driven by line and column drivers  906  well known in the art. The input image data (or target image data processed by the smart device) is stored in a frame buffer  908 . The image data is feed through the line and column driver to drive the liquid crystal in each pixel to a desired physical state such that each pixel in combination with other optical films such as a polarizer filters the back light (not shown) to the desired light level. The screen may include a touch panel  910 . Thus, the screen may be implemented as a touch screen to receive input signals from the user. The touch panel includes one or more touch sensors to sense touches, slips, and gestures on the touch panel. The touch sensors may not only sense a boundary of a touch or slip action, but also sense a period of time and a pressure associated with the touch or slip action. In some embodiments, the multimedia component  808  includes a front camera and/or a rear camera. The front camera and the rear camera may receive external stimuli and produce multimedia data while the device  800  is in an operation mode, such as a photographing mode or a video mode. Each of the front camera and the rear camera may be a camera system employing fixed optical lens or lens having focus and optical zoom capability. 
     The audio component  810  is configured to output and/or input audio signals. For example, the audio component  810  may include a microphone (“MIC”) configured to receive an external audio signal when the terminal device  800  is in an operation mode, such as a call mode, a recording mode, and a voice recognition and voice-command input mode. The received audio signal may be further stored in the memory  804  or transmitted via the communication component  816 . In some embodiments, the audio component  810  further includes a speaker to output audio signals. 
     The I/O interface  812  provides an interface between the processing component  802  and peripheral interface modules, such as keyboards, click wheels, and input push buttons. The buttons may include, but are not limited to, a home button, a volume button, a starting button, and a locking button. 
     The sensor component  814  includes one or more sensors to provide and assessing various status of the device  800 . For instance, the sensor component  814  may detect an open/closed status of the device  800 , relative physical position and/or orientation of components (e.g., the display and the keypad, of the device  800 ), a change in position and/or orientation of the device  800  or a component of the device  800 , a presence or absence of user contact/touch with the device  800 , an acceleration/deceleration of the device  800 , and/or a change in temperature of the device  800 . The sensor component  814  may further include a proximity sensor configured to detect the presence of nearby objects without any physical contact. The sensor component  814  may also include a light sensor, such as a CMOS or CCD image sensor, for use in imaging applications. In some embodiments, the sensor component  814  may also include one or more of accelerometers, gyroscopes, magnetic sensors, pressure sensors, and thermometers. 
     The communication component  816  is configured to facilitate wired or wireless communications between the device  800  and other devices. The device  800  may access a wireless network based on any communications standard, such as WiFi, 2G cellular networks, 3G cellular networks, LTE networks, 4G cellular networks, or a combination thereof. In one exemplary embodiment, the communication component  816  receives a broadcast signal or broadcast associated information from an external broadcast management system via a broadcast channel. In one exemplary embodiment, the communication component  816  further includes a near field communication (NFC) module to facilitate short-range communications. For example, the NFC module may be implemented based on a radio frequency identification (RFID) technology, an infrared data association (IrDA) technology, an ultra-wideband (UWB) technology, a Bluetooth (BT) technology, and other technologies. 
     In one exemplary embodiment, the device  800  may be implemented with one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), controllers, micro-controllers, microprocessors, or other electronic components, for performing the method described above. 
     In another exemplary embodiment, a non-transitory computer-readable storage medium is provided which includes instructions that may be executed by the processor  820  in the device  800  to perform the above-described methods. The non-transitory computer-readable storage medium may include but is not limited to a ROM, a RAM, a CD-ROM, a magnetic tape, a magnetic disk, a floppy disc, and an optical data storage device. 
     For example, the instructions stored in the non-transitory computer-readable medium may be executed in a mobile terminal. When the instructions are executed by a processor of the mobile terminal, the mobile terminal is configured to perform an image displaying method, which comprises: upon receipt of an instruction or request for displaying an image, acquiring the image; determining and locating an image region composed of at least three adjoining monochromatic sections in the requested image; when a difference in color value between each two adjacent ones of the adjoining monochromatic sections is less than a predetermined threshold value, determine and calculate one or more target color values using color values of the monochromatic sections in the image region; replacing color values of the image region in the requested image with the one or more target color values to generate a target image; and displaying the target image. 
     Each module or unit discussed above for  FIG. 5-10 , such as the acquiring module, the first determining module, the second determining module, the modifying module, the first display module, the first storage module, the first establishing module, the second establishing module, the third determining module, the fourth determining module, the second display module, the fifth determining module, the judging module, the triggering module, the third display module, the first calculation submodule, the determining submodule, the acquiring submodule, the second calculation module, the third calculation module, the fourth calculation module, the deleting module, the first storage module, and the second storage module, may take the form of a packaged functional hardware unit designed for use with other components, a portion of a program code (e.g., software or firmware) executable by the processor  820  or the processing circuitry that usually performs a particular function of related functions, or a self-contained hardware or software component that interfaces with a larger system, for example. 
     The illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The illustrations are not intended to serve as a complete description of all of the elements and features of apparatus and systems that utilize the structures or methods described herein. Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following the general principles thereof and including such departures from the present disclosure as come within known or customary practice in the art. It is intended that the specification and examples are considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims in addition to the disclosure. 
     It will be appreciated that the present disclosure is not limited to the exact construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes can be made without departing from the scope thereof. It is intended that the scope of the disclosure only be limited by the appended claims.