From 269d3c2fe63a85acc2425d7669ce46475264ac93 Mon Sep 17 00:00:00 2001
From: Jerome <furious.jet@gmail.com>
Date: Sun, 30 Apr 2023 10:51:36 +0200
Subject: [PATCH] Added bilinear interpolation (broken) to python version.

---
 Camera.py              |  9 +++++++--
 ImageProjectionTest.py | 45 ++++++++++++++++++++++++++++++++++--------
 2 files changed, 44 insertions(+), 10 deletions(-)

diff --git a/Camera.py b/Camera.py
index 88ac4d1..8867be5 100644
--- a/Camera.py
+++ b/Camera.py
@@ -80,10 +80,15 @@ def sph2equirectangular(p_sph, width, height):
     ''' Converts spherical coordinates to pixel coordinates of an equirectangular image. '''
     theta = p_sph[1]
     phi = p_sph[2]
-    i = int(np.round(((height - 1)*theta)/np.pi)) % height
-    j = int(np.round((width*(np.pi + phi))/(2.0*np.pi))) % width
+    i = np.mod(((height - 1)*theta)/np.pi, height)
+    j = np.mod((width*(np.pi + phi))/(2.0*np.pi), width)
     return [i,j]
 
+def sph2equirectangular_int(p_sph, width, height):
+    ''' Converts spherical coordinates to pixel coordinates of an equirectangular image. '''
+    i, j = sph2equirectangular(p_sph, width, height)
+    return [int(i), int(j)]
+
 def equirectangular2sph(i, j, width, height):
     return np.array([1.0, np.pi*(i/(height-1)), 2.0*np.pi*(j/width - 0.5)])
 
diff --git a/ImageProjectionTest.py b/ImageProjectionTest.py
index 97348bc..0647262 100644
--- a/ImageProjectionTest.py
+++ b/ImageProjectionTest.py
@@ -2,8 +2,23 @@ import numpy as np
 from Camera import *
 import matplotlib.pyplot as plt
 
-def update_pixel(surf, i, j, cam, img):
-    ''' Updates a pixel in a surface by projecting a ray from the camera to the sphere centered on the camera. '''
+def interp2_normalized(f00, f10, f01, f11, x, y):
+    a00 = f00
+    a10 = f10 - f00
+    a01 = f01 - f00
+    a11 = f11 - f10 - f01 + f00
+    return a00 + a10*x + a01*y + a11*x*y
+
+def interp2(x0, y0, x1, y1, f00, f10, f01, f11, x, y):
+    x_n = (x - x0)/(x1 - x0)
+    y_n = (y - y0)/(y1 - y0)
+    print(x_n, y_n)# DEBUG
+    return interp2_normalized(f00, f10, f01, f11, x_n, y_n)
+
+def update_pixel(surf, i, j, cam, img, interp_type='nearest'):
+    ''' Updates a pixel in a surface by projecting a ray from the camera to the sphere centered on the camera.
+        interp_type: 'linear' or 'nearest'
+    '''
     # Get the ray direction in inertial frame by projecting the pixel to the sphere
     p_sensor     = pixelToNormalizedCoordinates(i, j, surf.shape[1], surf.shape[0])
     p_sensor[0] *= -1
@@ -11,27 +26,41 @@ def update_pixel(surf, i, j, cam, img):
     ray_dir      = cam.compute_ray_dir_inertial_frame(p_sensor[0], p_sensor[1])
     ray_dir_sph  = cart2sph(ray_dir)
     i_img, j_img = sph2equirectangular(ray_dir_sph, img.shape[1], img.shape[0])
-    surf[i,j,:]  = img[i_img, j_img, :]
+    if interp_type == 'linear':
+        i0 = int(np.floor(i_img)) % img.shape[0]
+        j0 = int(np.floor(j_img)) % img.shape[1]
+        i1 = int(np.ceil(i_img)) % img.shape[0]
+        j1 = int(np.ceil(j_img)) % img.shape[1]
+        col = interp2(i0, j0, i1, j1, img[i0,j0,:], img[i1,j0,:], img[i0,j1,:], img[i1,j1,:], i_img, j_img)
+        # print(i0, j0, i1, j1, i_img, j_img, img[i0,j0,:], img[i1,j0,:], img[i0,j1,:], img[i1,j1,:], col)# debug
+        surf[i,j,:] = [int(col[0]), int(col[1]), int(col[2])]
+    else:
+        surf[i,j,:]  = img[int(i_img), int(j_img), :]
     return surf
 
 if __name__ == '__main__':
     deg = np.pi/180.
-    width = 60
+    width = 300
     height = int(width/2)
+    interp_type = 'linear'
     surf = np.zeros((height, width, 3), dtype=int)
     
     # load 360 image
     img = plt.imread('venise.jpg')
-    plt.figure()
-    plt.imshow(img)
+    
+    if 0: # display 360 image
+        plt.figure()
+        plt.imshow(img)
 
-    cam = Camera(FOV=90*deg).set_target([0.,1.,.8])
+    az = -10*deg
+    cam = Camera(FOV=10*deg).set_target([np.cos(az),np.sin(az),0.05])
+    # cam = Camera(FOV=90*deg).set_target([0.,1.,.8])
     # cam = Camera(FOV=90*deg,up=np.array([1.,0.,1.])).set_target([0.,0.,-1.])# straight down
     
     # update surface
     for i in range(height):
         for j in range(width):
-            surf = update_pixel(surf, i, j, cam, img)
+            surf = update_pixel(surf, i, j, cam, img, interp_type)
     plt.figure()
     plt.imshow(surf)