Absolute Difference - 2023.2 English

The absdiff function finds the pixel wise absolute difference between two input images and returns an output image. The input and the output images must be the XF_8UC1 type.

Where,

I_out(x, y) is the intensity of output image at (x,y) position.
I_in1(x, y) is the intensity of first input image at (x,y) position.
I_in2(x, y) is the intensity of second input image at (x,y) position.

API Syntax

template<int SRC_T, int ROWS, int COLS, int NPC=1, int XFCVDEPTH_IN_1 = _XFCVDEPTH_DEFAULT, int XFCVDEPTH_IN_2 = _XFCVDEPTH_DEFAULT, int XFCVDEPTH_OUT_1 = _XFCVDEPTH_DEFAULT>
void absdiff(
xf::cv::Mat< SRC_T,  ROWS,  COLS,  NPC,  XFCVDEPTH_IN_1>& src1,
xf::cv::Mat< SRC_T,  ROWS,  COLS,  NPC,  XFCVDEPTH_IN_2>& src2,
xf::cv::Mat< SRC_T,  ROWS,  COLS,  NPC,  XFCVDEPTH_OUT_1>& dst )

Parameter Descriptions

The following table describes the template and the function parameters.

Table 267 Table absdiff Parameter Description
Parameter	Description
SRC_T	Input and Output pixel type. Only 8-bit, unsigned, 1 and 3 channels are supported (XF_8UC1 and XF_8UC3)
ROWS	Maximum height of input and output image.
COLS	Maximum width of input and output image. Must be multiple of 8, for 8-pixel operation.
NPC	Number of pixels to be processed per cycle; possible options are XF_NPPC1 and XF_NPPC8 for 1 pixel and 8 pixel operations respectively.
XFCVDEPTH_IN_1	Depth of the input image
XFCVDEPTH_IN_2	Depth of the input image
XFCVDEPTH_OUT_1	Depth of the output image
src1	Input image
src2	Input image
dst	Output image

Resource Utilization

The following table summarizes the resource utilization in different configurations, generated using Vivado HLS 2019.1 tool for the Xczu9eg-ffvb1156-1-i-es1 FPGA, to process a grayscale HD (1080x1920) image.

Table 268 Table absdiff Function Resource Utilization Summary
Operating Mode	Operating Frequency (MHz)	Utilization Estimate
Operating Mode	Operating Frequency (MHz)	BRAM_18K	DSP_48Es	FF	LUT	CLB
1 Pixel	300	0	0	62	67	17
8 Pixel	150	0	0	67	234	39

Performance Estimate

The following table summarizes the performance in different configurations, as generated using Vivado HLS 2019.1 tool for the Xczu9eg-ffvb1156-1-i-es1, to process a grayscale HD (1080x1920) image.

Table 269 Table absdiff Function Performance Estimate Summary
Operating Mode	Latency Estimate
Operating Mode	Max Latency (ms)
1 pixel operation (300 MHz)	6.9
8 pixel operation (150 MHz)	1.69

Deviation from OpenCV

There is no deviation from OpenCV, except that the absdiff function supports 8-bit pixels.