Blur a region shaped like a rounded rectangle inside an Image

Question

I want to blur a rectangle (with rounded corners) in an image using python pillow. I already found a way to blur only a certain part of a picture.

img = Image.open('assets/images/image.png')
x, y = 300, 1600

cropped_img = img.crop((x, y, 1000, 2600))

blurred_img = cropped_img.filter(ImageFilter.GaussianBlur(20))

img.paste(blurred_img, (x, y))

img.save('assets/images/new.png')
img.show()

Furthermore I found a method to add rounded corners on a rectangle(Transparency issues drawing a rectangle with rounded corners)

def round_corner(radius):
   corner = Image.new('RGBA', (radius, radius), (0, 0, 0, 0))
   draw = ImageDraw.Draw(corner)
   draw.pieslice((0, 0, radius * 2, radius * 2), 180, 270)
   return corner

def round_rectangle(rectangle, radius):
   corner = round_corner(radius)
   rectangle.paste(corner, (0, 0))
   rectangle.paste(corner.rotate(90), (0, rectangle.size[1] - radius))
   rectangle.paste(corner.rotate(180), (rectangle.size[0] - radius,   rectangle.size[1] - radius))
   rectangle.paste(corner.rotate(270), (rectangle.size[0] - radius, 0))
   return rectangle

Unfortunately, I can't find a way to combine these two source codes so that they work.

My Example Image:

Answer 1

您需要做的，本质上是为Image.paste()仅粘贴位于圆角矩形内的模糊图像的那些部分创建一个蒙版。

import PIL
from PIL import Image
from PIL import ImageFilter
from PIL import ImageDraw

# when using an image as mask only the alpha channel is important
solid_fill =  (50,50,50,255) 


def create_rounded_rectangle_mask(rectangle, radius):
    # create mask image. all pixels set to translucent
    i = Image.new("RGBA",rectangle.size,(0,0,0,0))

    # create corner
    corner = Image.new('RGBA', (radius, radius), (0, 0, 0, 0))
    draw = ImageDraw.Draw(corner)
    # added the fill = .. you only drew a line, no fill
    draw.pieslice((0, 0, radius * 2, radius * 2), 180, 270, fill = solid_fill)

    # max_x, max_y
    mx,my = rectangle.size

    # paste corner rotated as needed
    # use corners alpha channel as mask

    i.paste(corner, (0, 0), corner)
    i.paste(corner.rotate(90), (0, my - radius),corner.rotate(90))
    i.paste(corner.rotate(180), (mx - radius,   my - radius),corner.rotate(180))
    i.paste(corner.rotate(270), (mx - radius, 0),corner.rotate(270))

    # draw both inner rects
    draw = ImageDraw.Draw(i)
    draw.rectangle( [(radius,0),(mx-radius,my)],fill=solid_fill)
    draw.rectangle( [(0,radius),(mx,my-radius)],fill=solid_fill)

    return i

面具：

将蒙版应用到您的图像：

img = Image.open('pic.jpg')

x, y = 300, 160 
radius = 75

cropped_img = img.crop((x, y, 600, 600))

# the filter removes the alpha, you need to add it again by converting to RGBA
blurred_img = cropped_img.filter(ImageFilter.GaussianBlur(20),).convert("RGBA")

# paste blurred, uses alphachannel of create_rounded_rectangle_mask() as mask 
# only those parts of the mask that have a non-zero alpha gets pasted
img.paste(blurred_img, (x, y), create_rounded_rectangle_mask(cropped_img,radius))

img.save('new2.png')
img.show()

我改变了一些尺寸和路径。您的代码缺少导入，我将其完成为一个最小的可验证完整示例。