How to do transparent color inside the boundry in python

Question

I have the images of brain tumor detection I want to do the transparent color inside the boundary of detection in python.

Transparent color will be same as the boundary color (122, 160, 255) with low opacity.

Image of Brain Tumor Detection

Expected Output: Expected Image

Does this answer your question? [Python PIL 0.5 opacity, transparency, alpha](https://stackoverflow.com/questions/24731035/python-pil-0-5-opacity-transparency-alpha) — Bilal, Feb 04 '23 at 08:39
Hey, you didnt add any code you tried, please edit your issue and add the code you tried to run so we can help you to debug the problem better — Mark Kapilyan, Feb 04 '23 at 08:43
How can rgb(122,160,255) be transparent? It doesn't have an alpha channel, i.e. it isn't RGBA. — Mark Setchell, Feb 04 '23 at 09:16
That doesn’t make much sense to me, sorry. Can you click [edit] and add an image of your expected output please? Even a mocked up version is fine. — Mark Setchell, Feb 04 '23 at 09:42
How is your boundary stored? Do you have a list of the boundary pixels? Or a black image with the boundary pixels in white? Or what? — Mark Setchell, Feb 04 '23 at 10:14

score 2 · Accepted Answer · answered Feb 04 '23 at 13:00

Here's a way of doing this:

load boundary image in greyscale and threshold
find approximate centre of tumour
flood-fill tumour interior with value=64, leaving boundary=255
create a peachy overlay same size as original
push the greyscale into the peachy overlay as alpha layer
paste the overlay onto original

#!/usr/bin/env python3

from PIL import Image, ImageDraw

# Open boundary image and ensure greyscale
im = Image.open('boundary.png').convert('L')

# Get the bounding box so we can guesstimate its centre for flood-filling
bbox = im.getbbox()
cx = int((bbox[0]+bbox[1])/2)
cy = int((bbox[2]+bbox[3])/2)
print(f'DEBUG: cx={cx}, cy={cy}')

# Threshold the boundary image to pure black and white
thresh = im.point(lambda p: 255 if p>128 else 0)

# Flood-fill with 64 starting from the centre and proceeding to a pure white boundary border
ImageDraw.floodfill(thresh, (cx,cy), 64, border=255)
thresh.save('DEBUG-flood-filled.png')

# Open the original image
scan = Image.open('a0pMX.png')

# Create a peachy overlay, then push in the alpha layer
overlay = Image.new('RGB', scan.size, 'rgb(255,160,122)')
overlay.putalpha(thresh)
overlay.save('DEBUG-overlay.png')

# Paste the overlay onto the scan
scan.paste(overlay, mask=overlay)
scan.save('result.png')

Here are the intermediate images:

DEBUG-flood-filled.png

DEBUG-overlay.png

result.png

How to do transparent color inside the boundry in python

1 Answers1