convert bmp img to png by using jni in android

本文主要讲解sobel的算法原理以及如何使用C++算法实现。通过JNI调用像素点，重新绘制生成沙子效果的图片(sand)-This paper mainly explains the principle of sobel and how to use the c++ algorithm. Redraw pictures of the sand effect by calling pixels by JNI.

使用JNI实现Sobel算子图像边缘检测(Using JNI to achieve Sobel operator image edge detection)