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  • 3.9.0

    • Laplacian Filter

    Laplacian filter is a second derivative operator commonly used in image processing, mainly for edge detection. It highlights regional changes in an image by calculating the second derivative of the image grayscale value. Since it is very sensitive to noise, the image is usually first Gaussian smoothed to reduce the impact of noise. The calculation of the Laplacian operator involves a convolution kernel on the image to obtain the second-order derivative value of each pixel in the image. These values ​​represent the rate of change of the pixel value in the image. This process can effectively detect the edges in the image.

    Operator Effect

    Input ImageParameterOutput Image
    imagekernelSize = 1
    borderType = HB_VP_BORDER_CONSTANT
    normalize = 0    		image

    Principle

    The main calculation process of Laplacian filter is to convolve the input image using a specific filter kernel. The main formula is as follows:

    dst=Δsrc=∂2src∂x2+∂2src∂y2{dst} = \Delta \text{src} = \frac{\partial^2 \text{src}}{\partial x^2} + \frac{\partial^2 \text{src}}{\partial y^2}

    The dstdst is the output image, srcsrc is the input image. Currently vp only supports OpenCV ksize = 1, [0, 1, 0, 1, -4, 1, 0, 1, 0].

    API Interface

    int32_t hbVPLaplacianFilter(hbUCPTaskHandle_t *taskHandle,
                            hbVPImage *dstImg,
                            hbVPImage const *srcImg,
                            hbVPLaplacianFilterParam const *laplacianParam);

    For detailed interface information, please refer to hbVPLaplacianFilter.

    Usage

    // Include the header
#include "hobot/hb_ucp.h"
#include "hobot/vp/hb_vp.h"
#include "hobot/vp/hb_vp_bilateral_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_S16C1,
                  dst_width,
                  dst_height,
                  dst_stride,
                  dst_mem.virAddr,
                  dst_mem.phyAddr,
                  nullptr,
                  0,
                  0};

// init param
hbVPLaplacianFilterParam vp_param;
vp_param.kernelSize = 1;
vp_param.borderType = HB_VP_BORDER_CONSTANT;
vp_param.normalize = 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
hbVPLaplacianFilter(&task_handle, &dst_img, &src_img, &vp_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);