我正在尝试将旋转图像在 Reportlab 上居中,但在使用正确的放置计算时遇到问题。
这是当前代码:
from reportlab.pdfgen import canvas
from reportlab.lib.utils import ImageReader
from PIL import Image as PILImage
import requests
import math
def main(rotation):
# create a new PDF with Reportlab
a4 = (595.275590551181, 841.8897637795275)
c = canvas.Canvas('output.pdf', pagesize=a4)
c.saveState()
# loading the image:
img = requests.get('https://i.stack.imgur.com/dI5Rj.png', stream=True)
img = PILImage.open(img.raw)
width, height = img.size
# We calculate the bouding box of a rotated rectangle
angle_radians = rotation * (math.pi / 180)
bounding_height = abs(width * math.sin(angle_radians)) + abs(height * math.cos(angle_radians))
bounding_width = abs(width * math.cos(angle_radians)) + abs(height * math.sin(angle_radians))
a4_pixels = [x * (100 / 75) for x in a4]
offset_x = (a4_pixels[0] / 2) - (bounding_width / 2)
offset_y = (a4_pixels[1] / 2) - (bounding_height / 2)
c.translate(offset_x, offset_y)
c.rotate(rotation)
c.drawImage(ImageReader(img), 0, 0, width, height, 'auto')
c.restoreState()
c.save()
if __name__ == '__main__':
main(45)
到目前为止,这就是我所做的:
出现两个问题我无法解释:
a4_pixels = [x * (100 / 75) for x in a4]
)。对于 0 度旋转,放置不正确。如果我将 a4 保留为点,它会起作用......?所以我的最后一个问题:如何计算
offset_x
和 offset_y
值以确保无论旋转如何它始终居中?
当您平移画布时,您实际上是在移动原点 (0,0),所有绘制操作都将与其相关。
所以在下面的代码中,我将原点移到了页面的中间。 然后我旋转“页面”并在“页面”上绘制图像。无需旋转图像,因为其画布轴已旋转。
from reportlab.pdfgen import canvas
from reportlab.lib.utils import ImageReader
from reportlab.lib.pagesizes import A4
from PIL import Image as PILImage
import requests
def main(rotation):
c = canvas.Canvas('output.pdf', pagesize=A4)
c.saveState()
# loading the image:
img = requests.get('https://i.stack.imgur.com/dI5Rj.png', stream=True)
img = PILImage.open(img.raw)
# The image dimensions in cm
width, height = img.size
# now move the canvas origin to the middle of the page
c.translate(A4[0] / 2, A4[1] / 2)
# and rotate it
c.rotate(rotation)
# now draw the image relative to the origin
c.drawImage(ImageReader(img), -width/2, -height/2, width, height, 'auto')
c.restoreState()
c.save()
if __name__ == '__main__':
main(45)