Gaussian Filter

ThexFGaussianBlurfunction applies Gaussian blur on the input image. Gaussian filtering is done by convolving each point in the input image with a Gaussian kernel.



Where,are the mean values and,are the variances in x and y directions respectively.In the GaussianBlur function, values of,are considered as zeroes and the values of,are equal.

API Syntax

template void xFGaussianBlur(xF::Mat & src, xF::Mat & dst, float sigma)

Parameter Descriptions

The following table describes the template and the function parameters.

Table 1.xFGaussianBlur Function Parameter Descriptions
Parameter Description
FILTER_SIZE Filter size. Filter size of 3 (XF_FILTER_3X3), 5 (XF_FILTER_5X5) and 7 (XF_FILTER_7X7) are supported.
BORDER_TYPE Border type supported is XF_BORDER_CONSTANT
SRC_T Input and output 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 values are XF_NPPC1 and XF_NPPC8 for 1 pixel and 8 pixel operations respectively.
src Input image
dst Output image
sigma Standard deviation of Gaussian filter

Resource Utilization

The following table summarizes the resource utilization of the Gaussian Filter in different configurations, generated usingVivado HLS 2017.1version tool for theXilinx Xczu9eg-ffvb1156-1-i-es1FPGA, to progress a grayscale HD (1080x1920) image.

Table 2.xFGaussianBlur Function Resource Utilization Summary
Operating Mode Filter Size

Operating Frequency

(MHz)

 Utilization Estimate
BRAM_18K DSP_48Es FF LUT CLB
1 pixel 3x3 300 3 17 3641 2791 610
5x5 300 5 27 4461 3544 764
7x7 250 7 35 4770 4201 894
8 pixel 3x3 150 6 52 3939 3784 814
5x5 150 10 111 5688 5639 1133
7x7 150 14 175 7594 7278 1518

Performance Estimate

The following table summarizes a performance estimate of the Gaussian Filter in different configurations, as generated usingVivado HLS 2017.1tool forXilinx Xczu9eg-ffvb1156-1-i-es11 FPGA, to process a grayscale HD (1080x1920) image.

Table 3.xFGaussianBlur Function Performance Estimate Summary
Operating Mode Filter Size Latency Estimate
Max Latency (ms)
1 pixel operation (300 MHz) 3x3 7.01
5x5 7.03
7x7 7.06
8 pixel operation (150 MHz) 3x3 1.6
5x5 1.7
7x7 1.74