3D LUT - 2024.1 English

Vitis Libraries

Release Date
2024-05-30
Version
2024.1 English

3D Look Up Tables (LUTs) may look similar to 1D LUTs in their principle of using value as mapping indexes to get the new value, they differ in the sense that they operate on three independent parameters. This drastically increases the number of mapped indexes to value pairs. For example, a combination of 3 individual 1D LUTs can map 2^n * 3 values where n is the bitdepth, whereas a 3D LUT processing 3 channels will have 2^n * 2^n * 2^n possible values.

Since all those huge number of values cannot be stored, only a subset of them are saved and the remaining values are computed through interpolation. The current implementation supports trilinear interpolation.

API Syntax

template <int LUTDIM, int SQLUTDIM, int INTYPE, int OUTTYPE, int ROWS, int COLS, int NPPC = 1, int URAM = 0, int XFCVDEPTH_IN_1 = _XFCVDEPTH_DEFAULT, int XFCVDEPTH_IN_2 = _XFCVDEPTH_DEFAULT, int XFCVDEPTH_OUT_1 = _XFCVDEPTH_DEFAULT>
void lut3d(xf::cv::Mat<INTYPE, ROWS, COLS, NPPC, XFCVDEPTH_IN_1>& in_img,
           xf::cv::Mat<XF_32FC3, SQLUTDIM, LUTDIM, NPPC, XFCVDEPTH_IN_2>& lut,
           xf::cv::Mat<OUTTYPE, ROWS, COLS, NPPC, XFCVDEPTH_OUT_1>& out_img,
           unsigned char lutdim)

The following table describes the template and the function parameters.

Table 750 Table 3D LUT Parameter Description
Parameter Description
LUTDIM Maximum dimension of input LUT
SQLUTDIM Squared value of maximum dimension of input LUT
INTYPE Input Pixel Type. XF_8UC3, XF_10UC3, XF_12UC3, XF_16UC3 supported
OUTTYPE Output Pixel Type. XF_8UC3, XF_10UC3, XF_12UC3, XF_16UC3 supported
ROWS Maximum height of input and output image
COLS Maximum width of input and output image
NPPC Number of Pixels to be processed per cycle. Only XF_NPPC1 supported
URAM Enable to map storage structures to UltraRAM.
XFCVDEPTH_IN_1 Depth of the input image.
XFCVDEPTH_IN_2 Depth of the input image.
XFCVDEPTH_OUT_1 Depth of the output image.
in_img Input image
lut Input lut
out_img Output image
lutdim Dimension of input lut

Resource Utilization

The following table summarizes the resource utilization of the kernel in different configurations, generated using Vitis HLS 2020.2 tool for the Xilinx Alveo U200 FPGA, to process a 4K image.

Table 751 Table 3D LUT Resource Utilization Summary
Operating Mode

Operating Frequency

(MHz)

Utilization Estimate        
BRAM_18K DSP_48Es FF LUT SLICE
1 pixel 300 30 40 | 9182 | 12039| 847

Performance Estimate

The following table summarizes a performance estimate of the kernel in different configurations, as generated using Vitis HLS 2020.2 tool for the Xilinx Alveo U200 FPGA, to process 4K image.

Table 752 Table 3D LUT Resource Utilization Summary
Operating Mode

Operating Frequency

(MHz)

Latency Estimate
Max (ms)
1 pixel 300 28.5