FAST Corner Detection - 2023.2 English

Vitis Libraries

Release Date
2023.2 English

Features from accelerated segment test (FAST) is a corner detection algorithm, that is faster than most of the other feature detectors.

The fast function picks up a pixel in the image and compares the intensity of 16 pixels in its neighborhood on a circle, called the Bresenham’s circle. If the intensity of 9 contiguous pixels is found to be either more than or less than that of the candidate pixel by a given threshold, then the pixel is declared as a corner. Once the corners are detected, the non-maximal suppression is applied to remove the weaker corners.

This function can be used for both still images and videos. The corners are marked in the image. If the corner is found in a particular location, that location is marked with 255, otherwise it is zero.

API Syntax

void fast(xf::cv::Mat<SRC_T, ROWS, COLS, NPC, XFCVDEPTH_IN_1> & _src_mat,xf::cv::Mat<SRC_T, ROWS, COLS, NPC, XFCVDEPTH_OUT_1> & _dst_mat,unsigned char _threshold)

Parameter Descriptions

The following table describes the template and the function parameters.

Table 505 Table fast Parameter Description
Parameter Description
NMS If NMS == 1, non-maximum suppression is applied to detected corners (keypoints). The value should be 0 or 1.
SRC_T Input pixel type. Only 8-bit, unsigned, 1-channel is supported (XF_8UC1)
ROWS Maximum height of input image.
COLS Maximum width of input image (must be a multiple of 8, for 8-pixel operation)
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.
XFCVDEPTH_IN_1 Depth of the input image.
XFCVDEPTH_OUT_1 Depth of the output image.
_src_mat Input image
_dst_mat Output image. The corners are marked in the image.
_threshol d Threshold on the intensity difference between the center pixel and its neighbors. Usually it is taken around 20.

Resource Utilization

The following table summarizes the resource utilization of the kernel for different configurations, generated using Vivado HLS 2019.1 for the Xczu9eg-ffvb1156-1-i-es1 FPGA, to process a grayscale HD (1080x1920) image with NMS.

Table 506 Table fast Function Resource Utilization Summary
Name Resource Utilization
1 pixel per clock operation 8 pixel per clock operation
300 MHz 150 MHz
BRAM_18K 10 20
DSP48E 0 0
FF 2695 7310
LUT 3792 20956
CLB 769 3519

Performance Estimate

The following table summarizes the performance of kernel for different configurations, as generated using Vivado HLS 2019.1 tool for the Xczu9eg-ffvb1156-1-i-es1, to process a grayscale HD (1080x1920) image with non-maximum suppression (NMS).

Table 507 Table fast Function Performance Estimate Summary
Operating Mode Operating Frequency (MHz) Filter Size Latency Estimate
Max (ms)
1 pixel 300 3x3 7
8 pixel 150 3x3 1.86