You to implement parts of your applications using native-code Use of native code in your Android applications.Īndroid applications run in the Dalvik virtual machine. The Android NDK is a toolset that lets you embed components that make NDK cannot access lots of APIs available in the Android SDK directly, and developing in NDK will always introduce extra complexity The third aspect is that we can optimize the critical code at an assembly level, which is aĬommon practice in desktop software development. With NEON, we can process multiple pixels at one time to reduce the processing time. The naive approach is to apply aĬonversion formula to every pixel (that is, over two million pixels). Pixels from the RGB color space to the YCbCr color space. Suppose we are to convert a photo of 1920x1280 One particular coding task example is the colorĬonversion for a video frame or a photo. Such as NEON, a Single Instruction Multiple Data (SIMD) technology, allowing multipleĭata elements to be processed in parallel. The second source for performance improvements at NDK is that native code allowsĭevelopers to make use of some processor features that are not accessible at Android SDK, Dalvik VM is specially designedįor systems with constrained hardware resources (memory space, processor Java code is run by Dalvik VM on Android. At Android 2.2 or higher,Ī Just-In-Time (JIT) compiler is added to Dalvik VM to analyze and optimize the Javaīyte-code while the program is running (for example, JIT can compile a part of theīyte-code to binary code before its execution). Firstly, the native code is compiled to a binary code and run directly on OS, while Java code is translated into Javaīyte-code and interpreted by Dalvik Virtual Machine (VM). The performance improvements can come from three sources. Native code for processor-intensive tasks. Many multimedia applications and video games use The composite image is may improve application performance. The encrypted image cats_encypt.jpg cannot be viewed directly. File Encryption, Decryption, Segmentation and Merge - Brief BookĪs shown in the image, two assets'images cats.jpg and image.jpg will be copied into the local sdcard/NdkSample directory for testing. The following exercises are for reference: NDK Development Foundation II. In addition, the segmentation and merging of files are performance-intensive, and can be put into NDK processing to improve efficiency. The file encryption and decryption is designed to be secure, and NDK can be used to increase the difficulty of decompilation. When needed, the split files can be merged. Generally, when large files are transmitted, such as audio and video files, the files will be divided and then transmitted, thus improving efficiency. The following is a relatively simple ^ XOR operation to encrypt and decrypt files (a symmetric encryption algorithm)Īttachment: Encryption and decryption algorithm expansion: Encryption and Decryption Algorithms, Block Chain Technical Guidelines So we can encrypt and decrypt files by binary operation. Encryption and Decryption of Files and Separation and Merge 1.1 INTRODUCTIONĪll files are stored in binary, whether text, pictures or video files are stored in binary on disk. Detailed introduction or code can be viewed by clicking on the links inside. It only records some points or main steps that individuals need to pay attention to. Because demo is introduced on these projects online, there will be no detailed step-by-step instructions on how to operate. So continue the actual battle of JNI Android NDK Development: JNI Practical Chapter This article is mainly about the practice of some small NDK projects. If we only study theory, do not practice, do not step on the pit, it is generally difficult to find real problems in practical projects, but also more difficult to deepen the understanding of technology.
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