Draw text on an angle (rotated) in Python

Question

我在 Python 中将文本绘制到numpy数组图像上（使用自定义字体）。目前我正在将图像转换为 PIL，绘制文本然后转换回 numpy 数组。

import numpy as np
import cv2

from PIL import Image
from PIL import ImageDraw
from PIL import ImageFont

char_image = np.zeros((200, 300, 3), np.uint8)

# convert to pillow image
pillowImage = Image.fromarray(char_image)
draw = ImageDraw.Draw(pillowImage)

# add chars to image
font = ImageFont.truetype("arial.ttf", 32)
draw.text((50, 50), 'ABC', (255, 255, 255), font=font)

# convert back to numpy array
char_image = np.array(pillowImage, np.uint8)

# show image on screen
cv2.imshow('myImage', char_image)
cv2.waitKey(0)

无论如何要在给定的角度绘制文本，即。33度？

绘制文本后旋转图像不是一种选择

Answer 1

您可以使用 PIL 绘制旋转文本。我建议将文本绘制到空白图像上，旋转该图像，然后将旋转后的图像粘贴到主图像中。就像是：

代码：

def draw_rotated_text(image, angle, xy, text, fill, *args, **kwargs):
    """ Draw text at an angle into an image, takes the same arguments
        as Image.text() except for:

    :param image: Image to write text into
    :param angle: Angle to write text at
    """
    # get the size of our image
    width, height = image.size
    max_dim = max(width, height)

    # build a transparency mask large enough to hold the text
    mask_size = (max_dim * 2, max_dim * 2)
    mask = Image.new('L', mask_size, 0)

    # add text to mask
    draw = ImageDraw.Draw(mask)
    draw.text((max_dim, max_dim), text, 255, *args, **kwargs)

    if angle % 90 == 0:
        # rotate by multiple of 90 deg is easier
        rotated_mask = mask.rotate(angle)
    else:
        # rotate an an enlarged mask to minimize jaggies
        bigger_mask = mask.resize((max_dim*8, max_dim*8),
                                  resample=Image.BICUBIC)
        rotated_mask = bigger_mask.rotate(angle).resize(
            mask_size, resample=Image.LANCZOS)

    # crop the mask to match image
    mask_xy = (max_dim - xy[0], max_dim - xy[1])
    b_box = mask_xy + (mask_xy[0] + width, mask_xy[1] + height)
    mask = rotated_mask.crop(b_box)

    # paste the appropriate color, with the text transparency mask
    color_image = Image.new('RGBA', image.size, fill)
    image.paste(color_image, mask)

它是如何工作的：

1. 创建一个透明蒙版。
2. 将文本绘制到蒙版上。
3. 旋转蒙版，并裁剪到合适的大小。
4. 使用包含文本的旋转透明蒙版将所需颜色粘贴到图像中。

测试代码：

import numpy as np

from PIL import Image
from PIL import ImageDraw
from PIL import ImageFont

char_image = np.zeros((100, 150, 3), np.uint8)

# convert to pillow image
pillowImage = Image.fromarray(char_image)

# draw the text
font = ImageFont.truetype("arial.ttf", 32)
draw_rotated_text(pillowImage, 35, (50, 50), 'ABC', (128, 255, 128), font=font)

pillowImage.show()

结果：

Answer 2

使用 matplotlib，首先可视化数组并在其上绘图，从图中获取原始数据。优点：这两种工具都相当高级，可以让您处理流程的许多细节。ax.annotate()提供了在何处以及如何绘制和设置字体属性的灵活性，并plt.matshow()提供了可让您处理数组可视化各个方面的灵活性。

import matplotlib.pyplot as plt
import scipy as sp

# make Data array to draw in
M = sp.zeros((500,500))

dpi = 300.0

# create a frameless mpl figure
fig, axes = plt.subplots(figsize=(M.shape[0]/dpi,M.shape[1]/dpi),dpi=dpi)
axes.axis('off')
fig.subplots_adjust(bottom=0,top=1.0,left=0,right=1)
axes.matshow(M,cmap='gray')

# set custom font
import matplotlib.font_manager as fm
ttf_fname = '/usr/share/fonts/truetype/ubuntu-font-family/Ubuntu-B.ttf'
prop = fm.FontProperties(fname=ttf_fname)

# annotate something
axes.annotate('ABC',xy=(250,250),rotation=45,fontproperties=prop,color='white')

# get fig image data and read it back to numpy array
fig.canvas.draw()
w,h = fig.canvas.get_width_height()
Imvals = sp.fromstring(fig.canvas.tostring_rgb(),dtype='uint8')
ImArray = Imvals.reshape((w,h,3))