Design of background and characters in mobile game by using image-processing methods

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1 , pp Design of background and characters in mobile game by using image-processing methods Young Jae Lee 1 1 Dept. of Smartmedia, Jeonju University, 303 Cheonjam-ro, Wansan-gu, Jeonju-si, , Korea leeyj@jj.ac.kr Abstract : Decisive factors for the success of a game are 'game background' and 'dynamic graphical changes of characters', which require complex graphical tasks such as special effects, and it presents great burden for game producers. Considering this reality, this paper proposes image-processing methods to generate various changes in colors, sizes, and shapes of backgrounds and characters in games. Among other image-processing methods, this paper uses 'gamma correction', 'invert image conversion', 'greyscale image conversion', 'sobel image conversion' for experiments in which images were changed and then applied to game background and character animation. Through the experiments, we could make the background and animation with dynamic image changes which help build up the environment where the game player is better immersed in the game activity. The proposed method may be used as the basic resource for game production using image-processing method. Keywords: Design, image-processing methods, background, characters 1 Introduction With wide use of mobile phones and advanced technologies in mobile communications, the global IT industry is entering the era of the wireless moving from its focus on the wired internet and the web. To create the mobile ecology, competitiveness in the hardware-including mobile gadgets- is not enough. The importance of software-os platform, applications, service development, and etc.- is getting larger and larger. In addition, as cloud computing is getting common with technological advancement in wireless communications including Wi-Fi and 4G/LTE, demand is increasing for animation contents such as multiscreen service and game.[1] The global game market is expected to increase to over 100 billion dollars in The mobile game which is showing dramatic increase is expected to excel consol in revenue from the year The game platform which shows the fastest growth rate is being realized through tablet PC, smart phone, and etc.[2] However, the mobile game platform, different from that of PC game, has limitations in its hardware environment, so effective operations are necessary. Especially burdensome to producers in terms of cost and time are 3D background, special effects and other tasks requiring complicated and big-volume graphical processes involving various ISSN: ASTL Copyright 2016 SERSC

2 characters.[3-4] As a solution to the above-mentioned problems, this paper proposes image-processing method, whose effectiveness is verified through experiments with game background and animation 2 Image Processing Digital image-processing is to process digital images gotten from the scanner or the digital camera to fit the specific needs. It is possible to transform original images to upgraded versions, or you can also recover the old corrupted or destroyed images. You can extract certain features from the digital image for your own use, or can create new images with partial images.[5] There are many kinds of image-processing methods developed. For the purpose of this paper, we use the methods which are applicable to game background and character graphics, and they are gamma correction, greyscale image conversion, invert conversion, and sobel conversion. 2.1 Gamma correction conversion Gamma correction of images is used to optimize the usage of bits when encoding an image, or bandwidth used to transport an image, by taking advantage of the non-linear manner in which humans perceive light and color. It is, in the simplest cases, defined by the following power-law expression: γ V =A V (1) out in where A is a constant and the input and output values are non-negative real values; in the common case of A = 1, inputs and outputs are typically in the range 0 1. A gamma value γ < 1 is sometimes called an encoding gamma, and the process of encoding with this compressive power-law nonlinearity is called gamma compression; conversely a gamma value γ > 1 is called a decoding gamma and the application of the expansive power-law nonlinearity is called gamma expansion.[6-7] 2.2 Greyscale image conversion Greyscale digital image is an image in which the value of each pixel is a single sample, that is, it carries only intensity information. Images of this sort, also known as black-and-white, are composed exclusively of shades of gray, varying from black at the weakest intensity to white at the strongest.[8] RGB values can be converted greyscale value by forming a weighted sum of the R,G and B components: G_value = * R * G * B (2) 104 Copyright 2016 SERSC

3 2.3 Invert image conversion The Invert command inverts all the pixel colors and brightness values in the current layer, as if the image were converted into a negative. Dark areas become bright and bright areas become dark. Hues are replaced by their complementary colors. For more information about colors, see the Glossary entry about Color Model.[9] R = Color.red_pixel_value, G = Color.green_pixel_value, (3) B = Color.blue_pixel_value 2.4 Sobel conversion The Sobel operator performs a 2-D spatial gradient measurement on an image and so emphasizes regions of high spatial frequency that correspond to edges. Typically it is used to find the approximate absolute gradient magnitude at each point in an input grayscale image. the operator consists of a pair of 3 3 convolution kernels as shown in Figure 1.These kernels are designed to respond maximally to edges running vertically and horizontally relative to the pixel grid, one kernel for each of the two perpendicular orientations. The kernels can be applied separately to the input image, to produce separate measurements of the gradient component in each orientation (call these Gx and Gy). These can then be combined together to find the absolute magnitude of the gradient at each point and the orientation of that gradient.[10] Fig. 1. Sobel convolution kernels 3 Experiment 3.1 Background experiment Experiment 3.1 is to generate the suitable background for the game by processing the images in the background. (a) (b) (c) (d) (e) Fig. 2. Input image of the background experiment and the resulting image after the imageprocessing method has been applied Copyright 2016 SERSC 105

4 Figure(a) is the input image of the background consisting of rocks, mountains, and trees. Figure(b) is the gamma correction of Figure(a). Gamma image is intended to show the best graphics within the limited range of the expressible information volume, and it increases the precision in the nonlinearly dark area. If you look at Figure(b), you can check that the part which is darker than the input image is highlighted. Therefore, this method can express the temporal movement information in an effective way in the mornings and evenings. Figure(c) is the invert image which can be used as the background where big environmental changes have happened such as collision, nuclear explosion, radiation leakage, and etc. The value is the inverse number for each RGB pixel. For Figure(d), the sobel method has been applied to extract the outlining data of the input image. Complex outlines of the objects in the image or the texture information are compared in black and white, which makes it clearer in expressing the concrete object outlines compared with the invert image of Figure(c). Figure(e) is the image transformed with gray conversion by using weight value for R,G,B color images. With this image, you can express new color information for the input image. Through experiment 1.1, with one background image, various kinds of images could be realized with various image-processing methods including gamma correction, invert image, greyscale image, and sobel image. 3.2 Character experiment 1 This experiment deals with ways to process images which can be effectively used for character animation in a game. Many characters in a game need various shapes, sizes and colors. In character experiment 1, image-processing method is applied to express various colors, which is then applied in animation. (a) (b) (c) (d) (e) Fig. 2. Input image for character experiment and the resulting character image after the imageprocessing method has been applied Figure(a) is one of the input images which are composed of seven frames. For each frame, methods of invert, gray, gamma correction, and sobel were used to convert frame images, and the converted frame images were applied in animation. Figure(b) is invert image; Figure(c), grey image; Figure(d), gamma correction image; Figure(d), sobel image. For the other three images, invert, gamma and grey methods were repetitively applied to be used in animation for experiment. The results of the experiment 3.2 showed that more effective expression was possible when the animation was applied with various image processing methods than when each frame was only varied in shapes without changes in colors of image. 106 Copyright 2016 SERSC

5 3.3 Character experiment 2 (a) (b) (c) (d) Fig. 3. Input images of the character experiment & the result character image after the imagetreating rotation method has been applied To increase fun in a game, we need various types of characters. The character experiment 2, to express various shapes, applies image-treating rotation method to characters. Figure(a) is the input image, and Figure(b) is the image of the input image rotated 15 degrees. Figure(c) is the image with 45 degrees of rotation. Figure(d) is the image of 90 degrees of rotation. Objects are rotated by using matrix, and we can adjust the rotating degrees to meet specific needs. 5 Conclusion Graphics of game background and characters are essential for the success of a game. Especially helping game players to get deeply immersed into the game experience are special effects used in events in a game, and variations in shapes, sizes, and colors of characters. For the sake of game immersion and various experiences for the players, this paper used various image-processing methods(gamma correction, grey image conversion, invert image conversion, and sobel conversion) and applied them to one image to change colors, shapes and sizes in the game. The experiment results showed dramatic variations in shapes, locations, and colors. However, this kind of process requires conversion time, so we need to generate one in the early routine. The proposed method could be used as the basic resource for image-processing method in the field of game applications. References 1. o=54&cpage=&st=tc&sv= 2. Global game trend, 2014, June ver.2 KOCCA Culture technology in-depth report, Trends of production technologies for 3D contents, 2010, July, KOCCA en.wikipedia.org/wiki/gamma_correction en.wikipedia.org/wiki/grayscale homepages.inf.ed.ac.uk/rbf/hipr2/sobel.htm Copyright 2016 SERSC 107