问题描述

是否可以通过 Matplotlib 在框中显示文本，自动换行?通过使用 pyplot.text()，我只能打印超出窗口边界的多行文本，这很烦人.事先不知道线条的大小......任何想法将不胜感激！

Is it possible to display text in a box through Matplotlib, with automatic line breaks? By using pyplot.text(), I was only able to print multi-line text that flows beyond the boundaries of the window, which is annoying. The size of the lines is not known in advance… Any idea would be much appreciated!

推荐答案

这个答案的内容被合并到了https://github.com/matplotlib/matplotlib/pull/4342 并将在下一个功能版本中.

The contents of this answer were merged into mpl master in https://github.com/matplotlib/matplotlib/pull/4342 and will be in the next feature release.

哇...这是一个棘手的问题...(并且它暴露了matplotlib的文本渲染中的很多限制...)

Wow... This is a thorny problem... (And it exposes a lot of limitations in matplotlib's text rendering...)

这应该(i.m.o.)是 matplotlib 内置的东西，但事实并非如此.有一些 关于它的线程邮件列表，但我找不到自动换行的解决方案.

This should (i.m.o.) be something that matplotlib has built-in, but it doesn't. There have been a few threads about it on the mailing list, but no solution that I could find to automatic text wrapping.

因此，首先，在 matplotlib 中绘制之前，无法确定渲染文本字符串的大小(以像素为单位).这不是太大的问题，因为我们可以绘制它，获取大小，然后重新绘制包装的文本.(虽然很贵，但也不算太差)

So, first off, there's no way to determine the size (in pixels) of the rendered text string before it's drawn in matplotlib. This isn't too large of a problem, as we can just draw it, get the size, and then redraw the wrapped text. (It's expensive, but not too excessively bad)

下一个问题是字符没有以像素为单位的固定宽度，因此将文本字符串包装到给定数量的字符不一定会在渲染时反映给定的宽度.不过，这不是一个大问题.

The next problem is that characters don't have a fixed width in pixels, so wrapping a text string to a given number of characters won't necessarily reflect a given width when rendered. This isn't a huge problem, though.

除此之外，我们不能只做一次......否则，它会在第一次绘制时正确包裹(例如在屏幕上)，但如果再次绘制(当图形调整大小或保存为与屏幕具有不同 DPI 的图像).这不是一个大问题，因为我们可以将回调函数连接到 matplotlib 绘制事件.

Beyond that, we can't just do this once... Otherwise, it will be wrapped correctly when drawn the first time (on the screen, for example), but not if drawn again (when the figure is resized or saved as an image with a different DPI than the screen). This isn't a huge problem, as we can just connect a callback function to the matplotlib draw event.

无论如何，这个解决方案是不完美的，但它应该适用于大多数情况.我不会尝试考虑 tex 渲染的字符串、任何拉伸字体或具有不寻常纵横比的字体.但是，它现在应该可以正确处理旋转的文本.

At any rate this solution is imperfect, but it should work in most situations. I don't try to account for tex-rendered strings, any stretched fonts, or fonts with an unusual aspect ratio. However, it should now properly handle rotated text.

但是，它应该尝试自动将任何文本对象包装在多个子图中，无论您将 on_draw 回调连接到哪个图形...它在许多情况下都是不完美的，但它做得不错.

However, It should attempt automatically wrap any text objects in multiple subplots in whichever figures you connect the on_draw callback to... It will be imperfect in many cases, but it does a decent job.

import matplotlib.pyplot as plt

def main():
    fig = plt.figure()
    plt.axis([0, 10, 0, 10])

    t = "This is a really long string that I'd rather have wrapped so that it"
    " doesn't go outside of the figure, but if it's long enough it will go"
    " off the top or bottom!"
    plt.text(4, 1, t, ha='left', rotation=15)
    plt.text(5, 3.5, t, ha='right', rotation=-15)
    plt.text(5, 10, t, fontsize=18, ha='center', va='top')
    plt.text(3, 0, t, family='serif', style='italic', ha='right')
    plt.title("This is a really long title that I want to have wrapped so it"
             " does not go outside the figure boundaries", ha='center')

    # Now make the text auto-wrap...
    fig.canvas.mpl_connect('draw_event', on_draw)
    plt.show()

def on_draw(event):
    """Auto-wraps all text objects in a figure at draw-time"""
    import matplotlib as mpl
    fig = event.canvas.figure

    # Cycle through all artists in all the axes in the figure
    for ax in fig.axes:
        for artist in ax.get_children():
            # If it's a text artist, wrap it...
            if isinstance(artist, mpl.text.Text):
                autowrap_text(artist, event.renderer)

    # Temporarily disconnect any callbacks to the draw event...
    # (To avoid recursion)
    func_handles = fig.canvas.callbacks.callbacks[event.name]
    fig.canvas.callbacks.callbacks[event.name] = {}
    # Re-draw the figure..
    fig.canvas.draw()
    # Reset the draw event callbacks
    fig.canvas.callbacks.callbacks[event.name] = func_handles

def autowrap_text(textobj, renderer):
    """Wraps the given matplotlib text object so that it exceed the boundaries
    of the axis it is plotted in."""
    import textwrap
    # Get the starting position of the text in pixels...
    x0, y0 = textobj.get_transform().transform(textobj.get_position())
    # Get the extents of the current axis in pixels...
    clip = textobj.get_axes().get_window_extent()
    # Set the text to rotate about the left edge (doesn't make sense otherwise)
    textobj.set_rotation_mode('anchor')

    # Get the amount of space in the direction of rotation to the left and 
    # right of x0, y0 (left and right are relative to the rotation, as well)
    rotation = textobj.get_rotation()
    right_space = min_dist_inside((x0, y0), rotation, clip)
    left_space = min_dist_inside((x0, y0), rotation - 180, clip)

    # Use either the left or right distance depending on the horiz alignment.
    alignment = textobj.get_horizontalalignment()
    if alignment is 'left':
        new_width = right_space 
    elif alignment is 'right':
        new_width = left_space
    else:
        new_width = 2 * min(left_space, right_space)

    # Estimate the width of the new size in characters...
    aspect_ratio = 0.5 # This varies with the font!! 
    fontsize = textobj.get_size()
    pixels_per_char = aspect_ratio * renderer.points_to_pixels(fontsize)

    # If wrap_width is < 1, just make it 1 character
    wrap_width = max(1, new_width // pixels_per_char)
    try:
        wrapped_text = textwrap.fill(textobj.get_text(), wrap_width)
    except TypeError:
        # This appears to be a single word
        wrapped_text = textobj.get_text()
    textobj.set_text(wrapped_text)

def min_dist_inside(point, rotation, box):
    """Gets the space in a given direction from "point" to the boundaries of
    "box" (where box is an object with x0, y0, x1, & y1 attributes, point is a
    tuple of x,y, and rotation is the angle in degrees)"""
    from math import sin, cos, radians
    x0, y0 = point
    rotation = radians(rotation)
    distances = []
    threshold = 0.0001 
    if cos(rotation) > threshold: 
        # Intersects the right axis
        distances.append((box.x1 - x0) / cos(rotation))
    if cos(rotation) < -threshold: 
        # Intersects the left axis
        distances.append((box.x0 - x0) / cos(rotation))
    if sin(rotation) > threshold: 
        # Intersects the top axis
        distances.append((box.y1 - y0) / sin(rotation))
    if sin(rotation) < -threshold: 
        # Intersects the bottom axis
        distances.append((box.y0 - y0) / sin(rotation))
    return min(distances)

if __name__ == '__main__':
    main()

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