如何平移/移動 python plot 中的梯度矩陣？

Question

語境

假設我有以下梯度矩陣：

[[0.         0.5        1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.5        1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.33333333 0.66666667 1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.33333333 0.66666667 1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.33333333 0.66666667 1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.33333333 0.66666667 1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.33333333 0.66666667 1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.33333333 0.66666667 1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.33333333 0.66666667 1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.         0.33333333 0.66666667 1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.         0.25       0.5        0.75       1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.         0.         0.33333333 0.66666667 1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.         0.         0.25       0.5        0.75       1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.         0.         0.         0.33333333 0.66666667 1.         0.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.         0.         0.         0.25       0.5        0.75       1.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.         0.         0.         0.25       0.5        0.75       1.         0.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.         0.         0.         0.         0.25       0.5        0.75       1.         0.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.         0.         0.         0.         0.2        0.4        0.6        0.8        1.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.         0.         0.         0.         0.         0.25       0.5        0.75       1.         0.         0.         0.         0.         0.         0.         0.        ]
 [0.         0.         0.         0.         0.         0.         0.         0.         0.         0.2        0.4        0.6        0.8        1.         0.         0.         0.         0.         0.         0.        ]]

產生以下 plot：

MWE

該圖像可以使用僅顯示跨矩陣運行的漸變的補丁創建：

import matplotlib.pyplot as plt
from matplotlib.patches import PathPatch
from matplotlib.path import Path
from scipy.ndimage import rotate


def generate_patch_plot():
    """Creates the geometry of the logo."""
    E=(8.0, 17.32050807568877)
    F=(10.0, 17.32050807568877)
    G=(16.0, 0)
    H=(20.0, 0.0)

    fig = plt.figure()
    ax = fig.add_subplot(111, aspect="equal")
    square_patch = Path([(0, 0), (0, 20), (20, 20), (20, 0), (0, 0)])
    square_path_patch = PathPatch(square_patch, facecolor="none")
    ax.add_patch(square_path_patch)
    gradient_matrix=[[0,0.6,0],[0,0.6,0],[0,0.6,0]]
    plt.plot(E[0], E[1], "ro", label="E")
    plt.plot(F[0], F[1], "yo", label="F")
    plt.plot(G[0], G[1], "bo", label="G")
    plt.plot(H[0], H[1], "co", label="H")
    im = plt.imshow(
        gradient_matrix,  # Gradient matrix
        interpolation="bilinear",
        origin="lower",  # Something
        cmap=plt.cm.hsv,
        extent=[0, 20, 0, 20],
        # extent=extension_domain,
        # clip_path=patch, # original.
        clip_path=square_path_patch,
        clip_on=True,
    )
    # im.set_clip_path(patch) # original.
    im.set_clip_path(square_path_patch)
    plt.show()

其中 E、F、G、H 是補丁的左上角、右上角、左下角、右下角坐標。 該補丁確保只有梯度在補丁內部可見，矩陣的 rest 在補丁外部被忽略。 但是，當我查看生成的 plot 時，矩陣從左上角繪制在y=0到y=15處。

問題

如何將要顯示的矩陣從 x = 4 移動到 -24，以及從 y = 7 移動到 -27？

Answer 1

在某個位置/偏移處繪制顏色漸變補丁的 XY 問題可以使用patch和extend來實現。 下面的代碼生成 3 個具有不同顏色漸變矩陣和不同顏色貼圖的獨立補丁：

代碼

# -*- coding: utf-8 -*-
"""Generates three separate patches with a colour gradient that co-exist in the
same geometry."""


import matplotlib.pyplot as plt
from matplotlib.patches import PathPatch
from matplotlib.path import Path

from src.create_gradient import re_order_coordinates


def generate_patch_plot():
    """Creates the geometry of the logo."""
    E = (8.0, 17.32050807568877)
    F = (10.0, 17.32050807568877)
    G = (16.0, 0)
    H = (20.0, 0.0)

    fig = plt.figure()
    ax = fig.add_subplot(111, aspect="equal")

    # Create gradient matrix for that segment.
    gradient_matrix_top_right = [[0, 0, 0], [0, 0.6, 0], [0, 0.6, 0]]
    gradient_matrix_mid = [[0, 0, 0], [1, 1, 1], [0, 0, 0]]
    gradient_matrix_bottom_left = [[1, 0, 0], [0, 1, 0], [0, 0, 1]]
    # First row is on bottom, last row on top.

    # Plot the patch coordinates.
    # TODO: shift left and down for manual verification.
    plt.plot(E[0], E[1], "ro", label="E")
    plt.plot(F[0], F[1], "yo", label="F")
    plt.plot(G[0], G[1], "bo", label="G")
    plt.plot(H[0], H[1], "co", label="H")

    extent_one = [0, 1, 0, 1]
    extent_two = [1, 2, 1, 2]
    extent_three = [-1, -2, -1, -2]

    # Create the first image
    plt.imshow(
        gradient_matrix_top_right,  # Gradient matrix
        interpolation="bilinear",
        origin="lower",  # Something
        cmap=plt.cm.hsv,
        extent=extent_one,
        # extent=extension_domain,
        # clip_path=patch, # original.
        clip_path=add_first_patch(ax),
        clip_on=True,
    )

    # Create the second
    plt.imshow(
        gradient_matrix_mid,  # Gradient matrix
        interpolation="bilinear",
        origin="lower",  # Something
        cmap=plt.cm.summer_r,
        extent=extent_two,
        # extent=extension_domain,
        # clip_path=patch, # original.
        clip_path=add_second_patch(ax),
        clip_on=True,
    )

    # Create the bottom left image
    plt.imshow(
        gradient_matrix_bottom_left,  # Gradient matrix
        interpolation="bilinear",
        origin="lower",  # Something
        cmap=plt.cm.summer_r,
        extent=extent_three,
        # extent=extension_domain,
        # clip_path=patch, # original.
        clip_path=add_third_patch(ax),
        clip_on=True,
    )

    # im.set_clip_path(patch) # original.
    # im.set_clip_path(square_path_patch)
    ax.set_xlim((-2, 2))
    ax.set_ylim((-2, 2))
    plt.show()


def create_4_coord_patch(top_left, top_right, bottom_left, bottom_right):
    """Generate a patch that describes the visible part of the gradient
    matrix."""
    top_left, top_right, bottom_left, bottom_right = re_order_coordinates(
        top_left, top_right, bottom_left, bottom_right
    )
    square_patch = Path(
        [top_left, top_right, bottom_right, bottom_left, top_left]
    )
    print(square_patch)
    square_path_patch = PathPatch(square_patch, facecolor="none")
    return square_path_patch


def create_square_patch(top_left, top_right, bottom_left, bottom_right):
    """Generate a patch that describes the visible part of the gradient
    matrix."""
    top_left, top_right, bottom_left, bottom_right = re_order_coordinates(
        top_left, top_right, bottom_left, bottom_right
    )
    bottom_left = (0, 0)
    top_left = (0, top_left[1])
    top_right = (400, 20)

    square_patch = Path(
        [top_left, top_right, bottom_right, bottom_left, top_left]
    )
    print(square_patch)
    square_path_patch = PathPatch(square_patch, facecolor="none")
    return square_path_patch


def add_first_patch(ax):
    """Adds a patch to the top right of the plot."""
    # First patch.
    top_left = (0, 1)
    top_right = (1, 1)
    bottom_left = (0, 0)
    bottom_right = (1, 0)
    square_path_patch_one = create_4_coord_patch(
        top_left, top_right, bottom_left, bottom_right
    )
    ax.add_patch(square_path_patch_one)
    return square_path_patch_one


def add_second_patch(ax):
    """Adds a patch to the top right of the origin of the plot."""
    # Second patch.
    top_left = (1, 2)
    top_right = (2, 2)
    bottom_left = (1, 1)
    bottom_right = (2, 1)
    square_path_patch_two = create_4_coord_patch(
        top_left, top_right, bottom_left, bottom_right
    )
    ax.add_patch(square_path_patch_two)
    return square_path_patch_two


def add_third_patch(ax):
    """Adds a patch to the bottom left of the origin of the plot."""
    # Third patch.
    top_left = (-2, -1)
    top_right = (-1, -1)
    bottom_left = (-2, -2)
    bottom_right = (-1, -2)
    square_path_patch_three = create_4_coord_patch(
        top_left, top_right, bottom_left, bottom_right
    )
    ax.add_patch(square_path_patch_three)
    return square_path_patch_three

Output