docs/ncnn_conversion.md

Instructions on converting to NCNN models

1. Convert to onnx model with scripts/pytorch2onnx.py. Remember to modify codes accordingly
2. Convert onnx model to ncnn model
   1. cd ncnn-master\ncnn\build\tools\onnx
   2. onnx2ncnn.exe realesrgan-x4.onnx realesrgan-x4-raw.param realesrgan-x4-raw.bin
3. Optimize ncnn model
   1. fp16 mode
      1. cd ncnn-master\ncnn\build\tools
      2. ncnnoptimize.exe realesrgan-x4-raw.param realesrgan-x4-raw.bin realesrgan-x4.param realesrgan-x4.bin 1
4. Modify the blob name in realesrgan-x4.param: data and output