Median Blur Filter - 2023.2 English

The function medianBlur performs a median filter operation on the input image. The median filter acts as a non-linear digital filter which improves noise reduction. A filter size of N would output the median value of the NxN neighborhood pixel values, for each pixel.

API Syntax

template<int FILTER_SIZE, int BORDER_TYPE, int TYPE, int ROWS, int COLS, int NPC, int XFCVDEPTH_IN = _XFCVDEPTH_DEFAULT, int XFCVDEPTH_OUT = _XFCVDEPTH_DEFAULT>
void medianBlur (xf::cv::Mat<TYPE, ROWS, COLS, NPC, XFCVDEPTH_IN> & _src, xf::cv::Mat<TYPE, ROWS, COLS, NPC, XFCVDEPTH_OUT> & _dst)

Parameter Descriptions

The following table describes the template and the function parameters.

Table 649 Table . medianBlur Parameter Description
Parameter	Description
FILTER_SIZE	Window size of the hardware filter for which the hardware kernel will be built. This can be any odd positive integer greater than 1.
BORDER_TYPE	The way in which borders will be processed in the hardware kernel. Currently, only XF_BORDER_REPLICATE is supported.
TYPE	Input and Output pixel type. Only 8-bit, unsigned, 1 and 3 channels are supported (XF_8UC1 and XF_8UC3)
ROWS	Number of rows in the image being processed.
COLS	Number of columns in the image being processed. Must be a multiple of 8, for 8-pixel operation.
NPC	Number of pixels to be processed in parallel. Options are XF_NPPC1 (for 1 pixel processing per clock), XF_NPPC8 (for 8 pixel processing per clock
XFCVDEPTH_IN	Depth of the input image.
XFCVDEPTH_OUT	Depth of the output image.
_src	Input image.
_dst	Output image.

Resource Utilization

The following table summarizes the resource utilization of the medianBlur function for XF_NPPC1 and XF_NPPC8 configurations, generated using Vivado HLS 2019.1 version tool for the Xczu9eg-ffvb1156-1-i-es1 FPGA.

Table 650 Table . medianBlur Function Resource Utilization Summary
Operating Mode	FILTER_SIZE	Operating Frequency (MHz)	Utilization Estimate
Operating Mode	FILTER_SIZE	Operating Frequency (MHz)	LUTs	FFs	DSPs	BRAMs
1 pixel	3	300	1197	771	0	3
8 pixel	3	150	6559	1595	0	6
1 pixel	5	300	5860	1886	0	5

The following table summarizes the resource utilization of the medianBlur function for XF_NPPC1 with 3channel image as input, generated using Vivado HLS 2019.1 version tool for the Xczu9eg-ffvb1156-1-i-es1 FPGA.

Table 651 Table . medianBlur Function Resource Utilization Summary
Operating Mode	FILTER_SIZE	Operating Frequency (MHz)	Utilization Estimate
Operating Mode	FILTER_SIZE	Operating Frequency (MHz)	LUTs	FFs	DSPs	BRAMs
1 pixel	3	300	2100	1971	0	9
1 pixel	5	300	13541	9720	0	15

Performance Estimate

The following table summarizes performance estimates of medianBlur function on Vivado HLS 2019.1 version tool for the Xilinx Xczu9eg-ffvb1156-1-i-es1 FPGA.

Table 652 Table . medianBlur Function Performance Estimate Summary
Operating Mode	FILTER_SIZE	Operating Frequency (MHz)	Input Image Size	Latency Estimate
Operating Mode	FILTER_SIZE	Operating Frequency (MHz)	Input Image Size	Max (ms)
1 pixel	3	300	1920x1080	6.99
8 pixel	3	150	1920x1080	1.75
1 pixel	5	300	1920x1080	7.00