Pyramid Down

The xFPyrDown function is an image down-sampling algorithm which smoothens the image before down-scaling it. The image is smoothened using a Gaussian filter with the following kernel:

Down-scaling is performed by dropping pixels in the even rows and the even columns. The resulting image size is

API Syntax

template<int TYPE, int ROWS, int COLS, int NPC> 
void xFPyrDown (xF::Mat<TYPE, ROWS, COLS, NPC> & _src, xF::Mat<TYPE, ROWS, COLS, NPC> & _dst)

Parameter Descriptions

The following table describes the template and the function parameters.

Table 1. xFPyrDown Function Parameter Descriptions
Parameter	Description
TYPE	Pixel type. XF_8UC1 is the only supported pixel type.
ROWS	Maximum Height or number of input rows to build the hardware for this kernel
COLS	Maximum Width or number of input columns to build the hardware for this kernel
NPC	Number of pixels to process per cycle. Currently, the kernel supports only 1 pixel per cycle processing (XF_NPPC1).
_src	Input image stream
_dst	Output image stream

Resource Utilization

The following table summarizes the resource utilization of xFPyrDown for 1 pixel per cycle implementation, for a maximum input image size of 1920x1080 pixels. The results are after synthesis in Vivado HLS 2017.1 for the Xilinx xczu9eg-ffvb1156-1-i-es1 FPGA at 300 MHz.

Table 2. xFPyrDown Function Resource Utilization Summary
Operating Mode	Operating Frequency (MHz)	Utilization Estimate
Operating Mode	Operating Frequency (MHz)	LUTs	FFs	DSPs	BRAMs
1 Pixel	300	1171	1238	1	5

Performance Estimate

The following table summarizes performance estimates of xFPyrDown function in Vivado HLS 2017.1 for the Xilinx xczu9eg-ffvb1156-1-i-es1 FPGA.

Table 3. xFPyrDown Function Performance Estimate Summary
Operating Mode	Operating Frequency (MHz)	Input Image Size	Latency Estimate
Operating Mode	Operating Frequency (MHz)	Input Image Size	Max (ms)
1 pixel	300	1920x1080	6.99