#Box Filter
盒滤波是一种低通滤波器，它通过将像素点周围的像素加权平均后得到生成像素值，常用来消除图片细节、去噪声、模糊边缘等。
#算子效果
| 输入图像 | 参数 | 输出图像 |
|---|---|---|
 | kernelHeight = 3 kernelWidth = 3 pointLocX = -1 pointLocY = -1 normalize = 1 borderType = 0 |  |
#原理
盒滤波使用以下滤波核，将滤波窗口内的像素值平均加权，计算得到输出图片的像素值：
boxm,n=mn111⋮111⋮1⋯⋯⋱⋯11⋮1
其中 m 和 n 为滤波核尺寸。
#API接口
int32_t hbVPBoxFilter(hbUCPTaskHandle_t *taskHandle,
hbVPImage *dstImg,
hbVPImage const *srcImg,
hbVPBoxFilterParam const *boxParam);
详细接口信息请查看 hbVPBoxFilter 。
#使用方法
// Include the header
#include "hobot/hb_ucp.h"
#include "hobot/vp/hb_vp.h"
#include "hobot/vp/hb_vp_box_filter.h"
// init Image, allocate memory for image data
hbUCPSysMem src_mem;
hbUCPMallocCached(&src_mem, src_stride * src_height, 0);
hbVPImage src_img{HB_VP_IMAGE_FORMAT_Y,
HB_VP_IMAGE_TYPE_U8C1,
src_width,
src_height,
src_stride,
src_mem.virAddr,
src_mem.phyAddr,
nullptr,
0,
0};
hbUCPSysMem dst_mem;
hbUCPMallocCached(&dst_mem, dst_stride * dst_height, 0);
hbVPImage dst_img{HB_VP_IMAGE_FORMAT_Y,
HB_VP_IMAGE_TYPE_U8C1,
dst_width,
dst_height,
dst_stride,
dst_mem.virAddr,
dst_mem.phyAddr,
nullptr,
0,
0};
// init param
hbVPBoxFilterParam box_filter_param;
box_filter_param.kernelHeight = 3;
box_filter_param.kernelWidth = 3;
box_filter_param.pointLocX = -1;
box_filter_param.pointLocY = -1;
box_filter_param.normalize = 1;
box_filter_param.borderType = 0;
// init task handle and schedule param
hbUCPTaskHandle_t task_handle{nullptr};
hbUCPSchedParam sched_param;
HB_UCP_INITIALIZE_SCHED_PARAM(&sched_param);
sched_param.backend = HB_UCP_DSP_CORE_0;
// create task
hbVPBoxFilter(&task_handle, &dst_img, &src_img, &box_filter_param);
// submit task
hbUCPSubmitTask(task_handle, &sched_param);
// wait for task done
hbUCPWaitTaskDone(task_handle, 0);
// release task handle
hbUCPReleaseTask(task_handle);
// release memory
hbUCPFree(&src_mem);
hbUCPFree(&dst_mem);
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