Absolute Difference

The xFabsdiff 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,
  • Iout(x, y) is the intensity of output image at (x,y) position.
  • Iin1(x, y) is the intensity of first input image at (x,y) position.
  • Iin2(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> 
void xFabsdiff(
xF::Mat<int SRC_T, int ROWS, int COLS, int NPC>  src1, 
xF::Mat<int SRC_T, int ROWS, int COLS, int NPC>  src2, 
xF::Mat<int SRC_T, int ROWS, int COLS, int NPC>  dst )

Parameter Descriptions

The following table describes the template and the function parameters.

Table 1. xFabsdiff Function Parameter Descriptions
Parameter Description
SRC_T Input pixel type. Only 8-bit, unsigned, 1 channel is supported (XF_8UC1)
ROWS Maximum height of input and output image (must be a multiple of 8)
COLS Maximum width of input and output image (must be a multiple of 8)
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.
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 2017.1 tool for the Xilinx Xczu9eg-ffvb1156-1-i-es1 FPGA, to process a grayscale HD (1080x1920) image.

Table 2. xFabsdiff Function Resource Utilization Summary
Operating Mode

Operating Frequency (MHz)

 Utilization Estimate
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 2017.1 tool for the Xilinx Xczu9eg-ffvb1156-1-i-es1, to process a grayscale HD (1080x1920) image.

Table 3. xFabsdiff Function Performance Estimate Summary
Operating Mode Latency Estimate
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 xFabsdiff function supports 8-bit pixels.