Android NDK 高斯模糊的实践

Android 高斯模糊的实践（DEMO级别）

• 掌握Android JNI的创建
  JNI创建，这个可以参考我之前的文章地址
  Android JNI创建
• 掌握什么是高斯模糊
  高斯模糊介绍链接
• 学习掌握高斯模糊算法
  高斯模糊算法介绍
• 利用代码进行实际操作实现
  来粘贴下主要的代码实现：

#include 
#include 
#include 
#include 
#include "android/bitmap.h"

#define PI 3.14

void gaussBlur(int *pInt, uint32_t width, uint32_t height, int i);

void gaussBlur(int *pix, uint32_t w, uint32_t h, int radius) {

    float sigma = (float) (1.0 * radius / 2.57);
    float deno = (float) (1.0 / (sigma * sqrt(2.0 * PI)));
    float nume = (float) (-1.0 / (2.0 * sigma * sigma));
    float *gaussMatrix = (float *) malloc(sizeof(float) * (radius + radius + 1));
    float gaussSum = 0.0;
    for (int i = 0, x = -radius; x <= radius; ++x, ++i) {
        float g = (float) (deno * exp(1.0 * nume * x * x));
        gaussMatrix[i] = g;
        gaussSum += g;
    }
    int len = radius + radius + 1;
    for (int i = 0; i < len; ++i)
        gaussMatrix[i] /= gaussSum;
    int *rowData = (int *) malloc(w * sizeof(int));
    int *listData = (int *) malloc(h * sizeof(int));
    for (int y = 0; y < h; ++y) {
        memcpy(rowData, pix + y * w, sizeof(int) * w);
        for (int x = 0; x < w; ++x) {
            float r = 0, g = 0, b = 0;
            gaussSum = 0;
            for (int i = -radius; i <= radius; ++i) {
                int k = x + i;
                if (0 <= k && k <= w) {
                    //得到像素点的rgb值
                    int color = rowData[k];
                    int cr = (color & 0x00ff0000) >> 16;
                    int cg = (color & 0x0000ff00) >> 8;
                    int cb = (color & 0x000000ff);
                    r += cr * gaussMatrix[i + radius];
                    g += cg * gaussMatrix[i + radius];
                    b += cb * gaussMatrix[i + radius];
                    gaussSum += gaussMatrix[i + radius];
                }
            }
            int cr = (int) (r / gaussSum);
            int cg = (int) (g / gaussSum);
            int cb = (int) (b / gaussSum);
            pix[y * w + x] = cr << 16 | cg << 8 | cb | 0xff000000;
        }
    }
    for (int x = 0; x < w; ++x) {
        for (int y = 0; y < h; ++y)
            listData[y] = pix[y * w + x];
        for (int y = 0; y < h; ++y) {
            float r = 0, g = 0, b = 0;
            gaussSum = 0;
            for (int j = -radius; j <= radius; ++j) {
                int k = y + j;
                if (0 <= k && k <= h) {
                    int color = listData[k];
                    int cr = (color & 0x00ff0000) >> 16;
                    int cg = (color & 0x0000ff00) >> 8;
                    int cb = (color & 0x000000ff);
                    r += cr * gaussMatrix[j + radius];
                    g += cg * gaussMatrix[j + radius];
                    b += cb * gaussMatrix[j + radius];
                    gaussSum += gaussMatrix[j + radius];
                }
            }
            int cr = (int) (r / gaussSum);
            int cg = (int) (g / gaussSum);
            int cb = (int) (b / gaussSum);
            pix[y * w + x] = cr << 16 | cg << 8 | cb | 0xff000000;
        }
    }
    free(gaussMatrix);
    free(rowData);
    free(listData);

}

• 注意事项：

1. 配置build.gradle 的 defaultConfig中添加

 ndk {
     abiFilters 'arm64-v8a', 'armeabi-v7a', 'x86', 'x86_64'
	}

2. 在CMakeLists.text 中需要配置 jnigraphics 库

# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

find_library( # Sets the name of the path variable.
        log-lib
        jnigraphics

        # Specifies the name of the NDK library that
        # you want CMake to locate.
        log)

• 总结：这可能是我最简洁的文章了，哈哈哈，希望大家别介意，即可完成简单的高斯模糊的实现；
  github代码