Histogram Equalization
TheequalizeHist
function performs histogram equalization on input image or video. It improves the contrast in the image, to stretch out the intensity range. This function maps one distribution (histogram) to another distribution (a wider and more uniform distribution of intensity values), so the intensities are spread over the whole range.
For histogram H[i], the cumulative distribution H'[i] is given as:
The intensities in the equalized image are computed as:
API Syntax
template void xFequalizeHist(xF::Mat & _src,xF::Mat & _src1,xF::Mat & _dst)
Parameter Descriptions
The following table describes the template and the function parameters.
Parameter | Description |
---|---|
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 |
_src | Input image |
_src1 | Input image |
_dst | Output image |
Resource Utilization
The following table summarizes the resource utilization of the equalizeHist function for Normal Operation (1 pixel) and Resource Optimized (8 pixel) configurations, generated usingVivado HLS 2017.1version tool for theXilinx Xczu9eg-ffvb1156-1-i-es1FPGA at 300 MHz for 1 pixel and 150 MHz for 8 pixel mode.
Operating Mode | Operating Frequency (MHz) |
Utilization Estimate | ||||
---|---|---|---|---|---|---|
BRAM_18K | DSP_48Es | FF | LUT | CLB | ||
1 pixel | 300 | 4 | 5 | 3492 | 1807 | 666 |
8 pixel | 150 | 25 | 5 | 3526 | 2645 | 835 |
Performance Estimate
The following table summarizes a performance estimate of the equalizeHist function for Normal Operation (1 pixel) and Resource Optimized (8 pixel) configurations, generated usingVivado HLS 2017.1version tool for theXilinx Xczu9eg-ffvb1156-1-i-es1FPGA at 300 MHz for 1 pixel and 150 MHz for 8 pixel mode.
Operating Mode | Latency Estimate |
---|---|
Max (ms) | |
1 pixel per clock operation | 13.8 |
8 pixel per clock operation |
3.4 |