kernel example

examples/kernel_interpolation.py

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+import numpy as np
+import darsia
+import skimage
+import matplotlib.pyplot as plt
+from pathlib import Path
+import matplotlib.patches as patches
+import string
+
+# import matplotlib.patches as patches
+
+folder = Path("images")
+baseline_path = folder / Path("20220914-142404.TIF")
+image_path = folder / Path("20220914-151727.TIF")
+# image_path = Path(".data/test/singletracer.JPG")
+
+# Setup curvature correction (here only cropping)
+curvature_correction = darsia.CurvatureCorrection(
+    config={
+        "crop": {
+            # Define the pixel values (x,y) of the corners of the ROI.
+            # Start at top left corner and then continue counterclockwise.
+            "pts_src": [[300, 600], [300, 4300], [7600, 4300], [7600, 600]],
+            # Specify the true dimensions of the reference points
+            "width": 0.92,
+            "height": 0.5,
+        }
+    }
+)
+transformations = [curvature_correction]
+
+# Read-in images
+baseline = darsia.imread(baseline_path, transformations=transformations).subregion(
+    voxels=(slice(2300, 2500), slice(2200, 5200))
+)
+image = darsia.imread(image_path, transformations=transformations).subregion(
+    voxels=(slice(2300, 2500), slice(2200, 5200))
+)
+
+
+# baseline_full = darsia.imread(baseline_path, transformations=transformations)
+# image_full = darsia.imread(image_path, transformations=transformations)
+
+
+# LAB
+diff_LAB = (
+    (skimage.color.rgb2lab(image.img) - skimage.color.rgb2lab(baseline.img))
+    + [0, 128, 128]
+) / [100, 255, 255]
+
+# RGB
+diff_RGB = skimage.img_as_float(image.img) - skimage.img_as_float(baseline.img)
+
+# HSV
+# diff = skimage.color.rgb2hsv(baseline.img) - skimage.color.rgb2hsv(image.img)
+
+# Regularize
+smooth_RGB = skimage.restoration.denoise_tv_bregman(
+    diff_RGB, weight=0.025, eps=1e-4, max_num_iter=100, isotropic=True
+)
+smooth_LAB = skimage.restoration.denoise_tv_bregman(
+    diff_LAB, weight=0.025, eps=1e-4, max_num_iter=100, isotropic=True
+)
+
+samples = [
+    (slice(50, 150), slice(100, 200)),
+    (slice(50, 150), slice(400, 500)),
+    (slice(50, 150), slice(600, 700)),
+    (slice(50, 150), slice(800, 900)),
+    (slice(50, 150), slice(1000, 1100)),
+    (slice(50, 150), slice(1200, 1300)),
+    (slice(50, 150), slice(1400, 1500)),
+    (slice(50, 150), slice(1600, 1700)),
+    (slice(50, 150), slice(2700, 2800)),
+]
+
+letters = list(string.ascii_uppercase)
+
+
+def extract_support_points(signal, samples):
+    # visualise patches
+    fig, ax = plt.subplots()
+    ax.imshow(np.abs(signal))  # visualise abs colours, because relative cols are neg
+    ax.set_xlabel("horizontal pixel")
+    ax.set_ylabel("vertical pixel")
+
+    # double check number of patches
+    n = np.shape(samples)[0]  # number of patches
+    print("number of support patches: " + str(n))
+
+    # init colour vector
+    colours = np.zeros((n, 3))
+    # enumerate through all patches
+    for i, p in enumerate(samples):
+        # visualise patches on image
+        rect = patches.Rectangle(
+            (p[1].start, p[0].start),
+            p[1].stop - p[1].start,
+            p[0].stop - p[0].start,
+            linewidth=1,
+            edgecolor="w",
+            facecolor="none",
+        )
+        # ax.text(
+        #     p[1].start + 130, p[0].start + 100, letters[i], fontsize=15, color="white"
+        # )
+        ax.text(p[1].start + 5, p[0].start + 95, letters[i], fontsize=12, color="white")
+        ax.add_patch(rect)
+
+        # histo analysis
+        patch = signal[p]
+        flat_image = np.reshape(patch, (10000, 3))  # all pixels in one dimension
+        # patch visualisation
+        # plt.figure("patch" + letters[i])
+        # plt.imshow(np.abs(patch))
+        H, edges = np.histogramdd(
+            flat_image, bins=100, range=[(-1, 1), (-1, 1), (-1, 1)]
+        )
+        print(H.shape)
+        index = np.unravel_index(H.argmax(), H.shape)
+        col = [
+            (edges[0][index[0]] + edges[0][index[0] + 1]) / 2,
+            (edges[1][index[1]] + edges[1][index[1] + 1]) / 2,
+            (edges[2][index[2]] + edges[2][index[2] + 1]) / 2,
+        ]
+        colours[i] = col
+
+    c = np.abs(colours)
+    plt.figure()
+    ax = plt.axes(projection="3d")
+    ax.set_xlabel("R*")
+    ax.set_ylabel("G*")
+    ax.set_zlabel("B*")
+    ax.scatter(colours[:, 0], colours[:, 1], colours[:, 2], c=c)
+    for i, c in enumerate(colours):
+        ax.text(c[0], c[1], c[2], letters[i])
+
+    print("characteristic colours: " + str(colours))
+    return n, colours
+
+
+n, colours_RGB = extract_support_points(signal=smooth_RGB, samples=samples)
+n, colours_LAB = extract_support_points(signal=smooth_LAB, samples=samples)
+concentrations = np.append(np.linspace(1, 0.99, n - 1), 0)
+
+
+def color_to_concentration(
+    k, colours, concentrations, signal: np.ndarray
+) -> np.ndarray:
+    # signal is rgb, transofrm to lab space because it is uniform and therefore
+    # makes sense to interpolate in
+    # signal = skimage.color.rgb2lab(signal)
+    # colours = skimage.color.rgb2lab(colours)
+
+    x = np.array(colours)  # data points / control points / support points
+    y = np.array(concentrations)  # goal points
+    X = np.ones((x.shape[0], x.shape[0]))  # kernel matrix
+    for i in range(x.shape[0]):
+        for j in range(x.shape[0]):
+            X[i, j] = k(x[i], x[j])
+
+    alpha = np.linalg.solve(X, y)
+
+    # Estimator / interpolant
+    def estim(signal):
+        sum = 0
+        for n in range(alpha.shape[0]):
+            sum += alpha[n] * k(signal, x[n])
+        return sum
+
+    # estim = scipy.interpolate.LinearNDInterpolator(colours, concentrations, 0)
+
+    ph_image = np.zeros(signal.shape[:2])
+    for i in range(signal.shape[0]):
+        for j in range(signal.shape[1]):
+            ph_image[i, j] = estim(signal[i, j])
+    return ph_image
+
+
+# define linear kernel shifted to avoid singularities
+def k_lin(x, y, a=0):
+    return np.inner(x, y) + a
+
+
+# define gaussian kernel
+def k_gauss(x, y, gamma=9.73):  # rgb: 9.73 , lab: 24.22
+    return np.exp(-gamma * np.inner(x - y, x - y))
+
+
+# Convert a discrete ph stripe to a numeric pH indicator.
+ph_image = color_to_concentration(
+    k_gauss, colours_RGB, concentrations, smooth_RGB
+)  # gamma=10 value retrieved from ph analysis kernel calibration war bester punk für c=0.95
+# was
+# physikalisch am meisten sinn ergibt
+
+plt.figure("cut ph val")
+plt.plot(np.average(ph_image, axis=0))
+plt.xlabel("horizontal pixel")
+plt.ylabel("concentration")
+
+ph_image[ph_image > 1] = 1  # für visualisierung von größer 1 values
+ph_image[ph_image < 0] = 0
+fig = plt.figure()
+fig.suptitle("evolution of signal processing in a subregion")
+ax = plt.subplot(212)
+ax.imshow(ph_image)
+# calibration patch for the kernel calibration visualization if needed
+# rect = patches.Rectangle(
+#     (1000, 80),
+#     40,
+#     40,
+#     linewidth=1,
+#     edgecolor="black",
+#     facecolor="none",
+# )
+# ax.add_patch(rect)
+ax.set_ylabel("vertical pixel")
+ax.set_xlabel("horizontal pixel")
+
+ax = plt.subplot(211)
+ax.imshow(skimage.img_as_ubyte(image.img))
+ax.set_ylabel("vertical pixel")
+ax.set_xlabel("horizontal pixel")
+
+# plt.figure("indicator")
+# indicator = np.arange(101) / 100
+# plt.axis("off")
+# plt.imshow([indicator, indicator, indicator, indicator, indicator])
+plt.show()