From f8a7d3fda6abef2923b0fa8f7021b9d0646ed8d5 Mon Sep 17 00:00:00 2001
From: yum <yum.food.vr@gmail.com>
Date: Sun, 27 Jul 2025 23:16:51 -0700
Subject: Fix twiddle factors in shader

---
 generate_fft_reference.py | 59 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 generate_fft_reference.py

(limited to 'generate_fft_reference.py')

diff --git a/generate_fft_reference.py b/generate_fft_reference.py
new file mode 100644
index 0000000..a7d58f4
--- /dev/null
+++ b/generate_fft_reference.py
@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+"""
+Generate reference FFT image in OpenEXR format, matching the shader's output format.
+"""
+
+import numpy as np
+import argparse
+from PIL import Image
+import OpenEXR
+import Imath
+
+def main():
+    parser = argparse.ArgumentParser(description='Generate reference FFT image')
+    parser.add_argument('input', type=str, help='Input image file')
+    parser.add_argument('output', type=str, help='Output EXR file')
+    parser.add_argument('--size', type=int, default=256, help='Size of the FFT (NxN)')
+    args = parser.parse_args()
+
+    # Load input image and convert to luminance
+    img = Image.open(args.input).convert('RGB')
+    img = img.resize((args.size, args.size), Image.Resampling.LANCZOS)
+    img_array = np.array(img, dtype=np.float32) / 255.0
+    luminance = 0.2126 * img_array[:,:,0] + 0.7152 * img_array[:,:,1] + 0.0722 * img_array[:,:,2]
+
+    # Perform 2D FFT (no fftshift, matching GPU implementation)
+    fft_result = np.fft.fft2(luminance)
+
+    # Pack complex numbers into RGBA matching shader format:
+    # R: real part, G: imaginary part, B: 0, A: 1
+    real_part = fft_result.real.astype(np.float32)
+    imag_part = fft_result.imag.astype(np.float32)
+
+    # Create EXR
+    height, width = args.size, args.size
+    header = OpenEXR.Header(width, height)
+    half_chan = Imath.Channel(Imath.PixelType(Imath.PixelType.FLOAT))
+    header['channels'] = {'R': half_chan, 'G': half_chan, 'B': half_chan, 'A': half_chan}
+
+    # Write EXR
+    out = OpenEXR.OutputFile(args.output, header)
+
+    # Create zero and one arrays for B and A channels
+    zeros = np.zeros((height, width), dtype=np.float32)
+    ones = np.ones((height, width), dtype=np.float32)
+
+    out.writePixels({
+        'R': real_part.astype(np.float32).tobytes(),
+        'G': imag_part.astype(np.float32).tobytes(),
+        'B': zeros.tobytes(),
+        'A': ones.tobytes()
+    })
+    out.close()
+
+    print(f"FFT complete. Output saved to {args.output}")
+    print(f"Real range: [{real_part.min():.1f}, {real_part.max():.1f}]")
+    print(f"Imag range: [{imag_part.min():.1f}, {imag_part.max():.1f}]")
+
+if __name__ == "__main__":
+    main()
-- 
cgit v1.2.3