matplotlib 进阶之origin and extent in imshow

文章目录

显示的extent
Explicit extent and axes limits

matplotlib教程学习笔记

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.gridspec import GridSpecdef index_to_coordinate(index, extent, origin):"""Return the pixel center of an index."""left, right, bottom, top = extenthshift = 0.5 * np.sign(right - left)left, right = left + hshift, right - hshiftvshift = 0.5 * np.sign(top - bottom)bottom, top = bottom + vshift, top - vshiftif origin == 'upper':bottom, top = top, bottomreturn {"[0, 0]": (left, bottom),"[M', 0]": (left, top),"[0, N']": (right, bottom),"[M', N']": (right, top),}[index]def get_index_label_pos(index, extent, origin, inverted_xindex):"""Return the desired position and horizontal alignment of an index label."""if extent is None:extent = lookup_extent(origin)left, right, bottom, top = extentx, y = index_to_coordinate(index, extent, origin)is_x0 = index[-2:] == "0]"halign = 'left' if is_x0 ^ inverted_xindex else 'right'hshift = 0.5 * np.sign(left - right)x += hshift * (1 if is_x0 else -1)return x, y, haligndef get_color(index, data, cmap):"""Return the data color of an index."""val = {"[0, 0]": data[0, 0],"[0, N']": data[0, -1],"[M', 0]": data[-1, 0],"[M', N']": data[-1, -1],}[index]return cmap(val / data.max())def lookup_extent(origin):"""Return extent for label positioning when not given explicitly."""if origin == 'lower':return (-0.5, 6.5, -0.5, 5.5)else:return (-0.5, 6.5, 5.5, -0.5)def set_extent_None_text(ax):ax.text(3, 2.5, 'equals\nextent=None', size='large',ha='center', va='center', color='w')def plot_imshow_with_labels(ax, data, extent, origin, xlim, ylim):"""Actually run ``imshow()`` and add extent and index labels."""im = ax.imshow(data, origin=origin, extent=extent)# extent labels (left, right, bottom, top)left, right, bottom, top = im.get_extent()if xlim is None or top > bottom:upper_string, lower_string = 'top', 'bottom'else:upper_string, lower_string = 'bottom', 'top'if ylim is None or left < right:port_string, starboard_string = 'left', 'right'inverted_xindex = Falseelse:port_string, starboard_string = 'right', 'left'inverted_xindex = Truebbox_kwargs = {'fc': 'w', 'alpha': .75, 'boxstyle': "round4"}ann_kwargs = {'xycoords': 'axes fraction','textcoords': 'offset points','bbox': bbox_kwargs}ax.annotate(upper_string, xy=(.5, 1), xytext=(0, -1),ha='center', va='top', **ann_kwargs)ax.annotate(lower_string, xy=(.5, 0), xytext=(0, 1),ha='center', va='bottom', **ann_kwargs)ax.annotate(port_string, xy=(0, .5), xytext=(1, 0),ha='left', va='center', rotation=90,**ann_kwargs)ax.annotate(starboard_string, xy=(1, .5), xytext=(-1, 0),ha='right', va='center', rotation=-90,**ann_kwargs)ax.set_title('origin: {origin}'.format(origin=origin))# index labelsfor index in ["[0, 0]", "[0, N']", "[M', 0]", "[M', N']"]:tx, ty, halign = get_index_label_pos(index, extent, origin,inverted_xindex)facecolor = get_color(index, data, im.get_cmap())ax.text(tx, ty, index, color='white', ha=halign, va='center',bbox={'boxstyle': 'square', 'facecolor': facecolor})if xlim:ax.set_xlim(*xlim)if ylim:ax.set_ylim(*ylim)def generate_imshow_demo_grid(extents, xlim=None, ylim=None):N = len(extents)fig = plt.figure(tight_layout=True)fig.set_size_inches(6, N * (11.25) / 5)gs = GridSpec(N, 5, figure=fig)columns = {'label': [fig.add_subplot(gs[j, 0]) for j in range(N)],'upper': [fig.add_subplot(gs[j, 1:3]) for j in range(N)],'lower': [fig.add_subplot(gs[j, 3:5]) for j in range(N)]}x, y = np.ogrid[0:6, 0:7]data = x + yfor origin in ['upper', 'lower']:for ax, extent in zip(columns[origin], extents):plot_imshow_with_labels(ax, data, extent, origin, xlim, ylim)for ax, extent in zip(columns['label'], extents):text_kwargs = {'ha': 'right','va': 'center','xycoords': 'axes fraction','xy': (1, .5)}if extent is None:ax.annotate('None', **text_kwargs)ax.set_title('extent=')else:left, right, bottom, top = extenttext = ('left: {left:0.1f}\nright: {right:0.1f}\n' +'bottom: {bottom:0.1f}\ntop: {top:0.1f}\n').format(left=left, right=right, bottom=bottom, top=top)ax.annotate(text, **text_kwargs)ax.axis('off')return columns

generate_imshow_demo_grid(extents=[None]);

通常来说，对于shape(M, N)来讲，M是沿着竖直方向的，而N是沿着水平方向的。
origin参数觉得了其实位置：

对于 origin=“lower”:

[0, 0] 在 (left, bottom)位置

[M, 0] 在 (left, upper)位置

[0, N] 在 (right, bottom)位置

[M, N] 在 (right, top) 位置

实际上就是，从左下角往右上角发展

而对于orgin=“upper”,则是从左上角往右下角发展

显示的extent

extent是控制图片的坐标轴的工具，为（left, right, bottom, top)
就是控制x轴为: left -> right
y轴为： bottom -> top

extents = [(-0.5, 6.5, -0.5, 5.5),(-0.5, 6.5, 5.5, -0.5),(6.5, -0.5, -0.5, 5.5),(6.5, -0.5, 5.5, -0.5)]columns = generate_imshow_demo_grid(extents)
set_extent_None_text(columns['upper'][1])
set_extent_None_text(columns['lower'][0])

Explicit extent and axes limits

搞不懂了啊，为什么加了limits之后，可以随便转来转去了啊不知道，就这样吧

generate_imshow_demo_grid(extents=[None] + extents,xlim=(-2, 8), ylim=(-1, 6));

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matplotlib 进阶之origin and extent in imshow

文章目录

显示的extent

Explicit extent and axes limits

matplotlib 进阶之origin and extent in imshow相关推荐

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