Accumulate Weighted

The xFaccumulateWeighted function computes the weighted sum of the input image (src1) and the accumulator image (src2) and generates the result in dst.

The accumulated result is a separate argument in the function, instead of having src2 as the accumulated result. In this implementation, having a bi-directional accumulator is not possible, as the function uses streams.

API Syntax

template<int SRC_T, int DST_T, int ROWS, int COLS, int NPC=1> 
void xFaccumulateWeighted (
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 DST_T, int ROWS, int COLS, int NPC> dst, 
float alpha )

Parameter Descriptions

The following table describes the template and the function parameters.

Table 1. xFaccumulateWeighted Function Parameter Descriptions
Parameter	Description
SRC_T	Input pixel type. Only 8-bit, unsigned, 1 channel is supported (XF_8UC1)
DST_T	Output pixel type. Only 16-bit, unsigned, 1 channel is supported (XF_16UC1)
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
alpha	Weight applied to input 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. xFaccumulateWeighted 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	5	295	255	52
8 pixel	150	0	19	556	476	88

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. xFaccumulateWeighted 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)	1.7

Deviation from OpenCV

The resultant image in OpenCV is stored in the second input image. The src2 image acts as input as well as output, as shown below:

Whereas, in xfOpenCV implementation, the accumulated weighted image is stored separately.