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  • 3.9.0

    • Box Filter

    The box filter is a low-pass filter that generates pixel values by weighting and averaging the pixels around a pixel point, and is commonly used to eliminate image details, remove noise, and blur edges.

    Operator Effect

    Input ImageParameterOutput Image
    imagekernelHeight = 3
    kernelWidth = 3
    borderType = HB_VP_BORDER_CONSTANT    		image

    Principle

    Box filtering uses the following filter kernel, which weights the pixel values within the filter window equally and calculates the pixel values of the output picture.

    boxm,n=1mn[11⋯111⋯1⋮⋮⋱⋮11⋯1]\begin{aligned}box_{m,n}=\frac{1}{mn}\begin{bmatrix}1 & 1 & \cdots & 1\\1 & 1 & \cdots & 1\\\vdots & \vdots & \ddots & \vdots\\1 & 1 & \cdots & 1\\\end{bmatrix}\end{aligned}

    mm and nn are the filter kernel sizes.

    API Interface

    int32_t hbVPBoxFilter(hbUCPTaskHandle_t *taskHandle,
                      hbVPImage *dstImg,
                      hbVPImage const *srcImg,
                      hbVPBoxFilterParam const *boxParam);

    For detailed interface information, please refer to hbVPBoxFilter.

    Usage

    // 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.borderType = HB_VP_BORDER_CONSTANT;

// 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);