图像到极坐标

Question

我在将图像转换为极坐标时遇到问题。在Photoshop中很容易：）所以这对我来说是一个新领域。

我有以下图片：

结果应该是这样的：

我在这里看了一下，了解了一些基本知识，但仍然对圆的平方有点困惑：

import math
from PIL import Image, ImageDraw


# image size
imgX = 200
imgY = 200

image = Image.new("RGB", (imgX, imgY))
draw = ImageDraw.Draw(image)

#fill with white first
colour = "#ffffff"
box = [0,0, imgX, imgY]
image.paste(colour, box)

# draw line near base
draw.line((0,180, 200, 180), fill="#FF0000", width=2)

print "Line done!"
image.save("line.png", "PNG")

# there's got to be a way to get the current image
# without having to open it up again

im = Image.open("line.png")
rgb_im = im.convert("RGB")

# rectangle to polar coordinates
maxradius = math.sqrt(imgX**2 + imgY**2)/2
rscale = imgX / maxradius
tscale = imgY / (2*math.pi)

for y in range(0, imgY):
    dy = y - imgY/2

    for x in range(0, imgX):
        dx = x - imgX/2
        t = math.atan2(dy,dx)%(2*math.pi)
        r = math.sqrt(dx**2+dy**2)

        r, g, b = rgb_im.getpixel((x, y))
        # this is where it goes wrong
        col = b * 65536 + g * 256 + r
        image.putpixel((x, y), b * 65536 + g * 256 + r

image.save("polar.png", "PNG")

我几乎不知道如何重新绘制图像。还有一个警告：由于管理限制，我想避免使用像Numpy这样的外部库。

Answer 1

以下代码适用于我。主要变化：

>

对于圆形图像中的每个对应的x和y，t和r将为您提供要在线条图像中访问的图像坐标。它们已经存在了，您只需要有效地将它们用作索引来获取像素颜色。

将rscale和tscale应用于r和t，使2×pi对应于图像的右边缘。您肯定需要更改r的这个比例，以便能够在输出中看到这个圆，或者将线向上画得更靠近顶部（例如，在第100行而不是180行）。

我还包括了一个线条图像访问的边界检查。

```

import math
from PIL import Image, ImageDraw     
# image size
imgX = 200
imgY = 200

line_image = Image.new("RGB", (imgX, imgY))
draw = ImageDraw.Draw(line_image)

#fill with white first
colour = "#ffffff"
box = [0,0, imgX, imgY]
line_image.paste(colour, box)

# draw line near base
draw.line((0,180, 200, 180), fill="#FF0000", width=2)

print "Line done!"
line_image.save("line.png", "PNG")

circle_image = Image.new("RGB", (imgX, imgY))

# rectangle to polar coordinates
maxradius = math.sqrt(imgX**2 + imgY**2)/2
rscale = imgX / maxradius
tscale = imgY / (2*math.pi)

for y in range(0, imgY):
    dy = y - imgY/2

    for x in range(0, imgX):
        dx = x - imgX/2
        t = math.atan2(dy,dx)%(2*math.pi)*tscale
        r = math.sqrt(dx**2+dy**2)*rscale

        if 0<= t < imgX and 0 <= r < imgY:
            r, g, b = line_image.getpixel((t, r))
            # this is where it goes wrong
            col = b * 65536 + g * 256 + r
            circle_image.putpixel((x, y), col)

circle_image.save("polar.png", "PNG")

```