3D LUT - 2023.2 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.

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.

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.