Pyramid Down

The xFPyrDownfunction 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 void xFPyrDown (xF::Mat & _src, xF::Mat & _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 inVivado HLS 2017.1for 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
LUTs FFs DSPs BRAMs
1 Pixel 300 1171 1238 1 5

Performance Estimate

The following table summarizes performance estimates of xFPyrDown function inVivado HLS 2017.1for 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
Max (ms)
1 pixel 300 1920x1080 6.99