Gradient Magnitude

ThexFmagnitudefunction computes the magnitude for the images. The input images are x-gradient and y-gradient images of type 16S. The output image is of same type as the input image.

For L1NORM normalization, the magnitude computed image is the pixel-wise added image of absolute of x-gradient and y-gradient, as shown below:.



For L2NORM normalization, the magnitude computed image is as follows:



API Syntax

template< int NORM_TYPE ,int SRC_T,int DST_T, int ROWS, int COLS,int NPC=1> void xFmagnitude(xF::Mat & _src_matx,xF::Mat & _src_maty,xF::Mat & _dst_mat)

Parameter Descriptions

The following table describes the template and the function parameters.

Table 1.xFmagnitude Function Parameter Descriptions
Parameter Description
NORM_TYPE Normalization type can be either L1 or L2 norm. Values are XF_L1NORM or XF_L2NORM
SRC_T Input pixel type. Only 16-bit, signed, 1 channel is supported (XF_16SC1)
DST_T Output pixel type. Only 16-bit, signed,1 channel is supported (XF_16SC1)
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_matx First input, x-gradient image.
_src_maty Second input, y-gradient image.
_dst_mat Output, magnitude computed image.

Resource Utilization

The following table summarizes the resource utilization of the kernel in different configurations, generated usingVivado HLS 2017.1tool for theXilinx Xczu9eg-ffvb1156-1-i-es1FPGA, to process a grayscale HD (1080x1920) image and for L2 normalization.

Table 2.xFmagnitude Function Resource Utilization Summary
Name Resource Utilization
1 pixel 8 pixel
300 MHz 150 MHz
BRAM_18K 0 0
DSP48E 2 16
FF 707 2002
LUT 774 3666
CLB 172 737

Performance Estimate

The following table summarizes the performance of the kernel in different configurations, as generated usingVivado HLS 2017.1tool for theXilinx Xczu9eg-ffvb1156-1-i-es1, to process a grayscale HD (1080x1920) image and for L2 normalization.

Table 3.xFmagnitude Function Performance Estimate Summary
Operating Mode

Operating Frequency (MHz)

 Latency Estimate
Max (ms)
1 pixel 300 7.2
8 pixel 150 1.7