ComputeThreshold_Otsu

Computes the value of the Otsu threshold. The calculation formula is as follows:

$\text{[math]}$

w0: ratio between the foreground pixels and the pixels of the entire image

wl: ratio between the background pixels and the pixels of the entire image, which is (1 – w0)

u0: grayscale value of the foreground pixels

u1: grayscale value of the background pixels

u: average value of the entire image

The function interface declaration is as follows:

Thresholding for single-channel data:

HmppResult HMPPI_ComputeThreshold_Otsu_8u_C1R(const uint8_t* src, int32_t srcStep, HmppiSize roiSize, uint8_t* threshold);

Parameters

Parameter	Description	Value Range	Input/Output
src	Pointer to the source image region of interest (ROI)	The value cannot be NULL.	Input
srcStep	Distance between starts of consecutive lines in the source image, in bytes	The value cannot be NULL.	Input
roiSize	Size of the ROI of the source and destination images, in pixels	roiSize.width ∈ (0, INT_MAX], roiSize.height ∈ (0, INT_MAX]	Input
threshold	Pointer to the Otsu threshold value	Range of the input data type	Output

Return Value

Success: HMPP_STS_NO_ERR
Failure: An error code is returned.

Error Codes

Error Code	Description
HMPP_STS_NULL_PTR_ERR	The value of src, dst, or srcDst is NULL.
HMPP_STS_SIZE_ERR	The width or height of roiSize is zero or negative.
HMPP_STS_STEP_ERR	The value of srcStep, dstStep, or srcDstStep is zero or negative.
HMPP_STS_ROI_ERR	roiSize.width > Step

Example

#define BUFFER_SIZE 36
int ComputeThreshold_Ostu()
{
    HmppiSize roi = { 9, 4 };
    const uint8_t src[BUFFER_SIZE] = { 1, 2, 4, 8, 16, 8, 4, 2, 1,
                                       1, 2, 4, 8, 16, 8, 4, 2, 1,
                                       1, 2, 4, 8, 16, 8, 4, 2, 1,
                                       1, 2, 4, 8, 16, 8, 4, 2, 1};
    uint8_t threshold;
    int32_t srcStep = 9 * sizeof(uint8_t);
    HmppResult result = HMPPI_ComputeThreshold_Otsu_8u_C1R(src, srcStep, roi, &threshold);

    printf("result = %d \n dst = ", result);
    if (result != HMPP_STS_NO_ERR) {
        printf("result error: %d\n", result);
    }
    printf("%d\n", threshold);
    return 0;
}

Output:

result = 0
dst = 4

Parent topic: Basic Operations