I am drawing a blue rectangle in framebuffer, and I want to erase it again. Before I draw the rectangle I copy the background where the rectangle will be pasted, and paste it over the rectangle after 2 seconds. The rectangle is not erased.
#!/usr/bin/env python
import numpy as np
import time
from PIL import Image
from io import BytesIO
h, w, c = 1024, 1280, 4
fb = np.memmap('/dev/fb0', dtype='uint8',mode='w+', shape=(h,w,c))
x0, y0 = 50, 200
w, h = 300, 400
# Copy backbround: Does not work?
n0 = fb.read[y0:y0+h, x0:x0+w]
# Paste blue rectangle to framebuffer: This works.
img = Image.new('RGBA', size=(w, h), color=(255,0,0,255))
n = np.array(img)
fb[y0:y0+h, x0:x0+w] = n
# Erase image: Does not work?
time.sleep(2)
fb[y0:y0+h, x0:x0+w] = n0
What am I doing wrong? If I paste n0 to another place in framebuffer, I get a blue rectangle, not a black one.
I solved it myself by using np.copy:
import numpy as np
import time
from PIL import Image
h, w, c = 1024, 1280, 4
fb = np.memmap('/dev/fb0', dtype='uint8',mode='w+', shape=(h,w,c))
x0, y0 = 50, 200
w, h = 300, 400
# Copy background:
### n0 = fb.read[y0:y0+h, x0:x0+w]
n0 = np.copy(fb[y0:y0+h, x0:x0+w])
# Paste blue rectangle to framebuffer: This works.
img = Image.new('RGBA', size=(w, h), color=(255,0,0,255))
n = np.array(img)
fb[y0:y0+h, x0:x0+w] = n
# Erase image:
time.sleep(2)
### fb[y0:y0+h, x0:x0+w] = n0
fb[y0:y0+h, x0:x0+w] = np.copy(n0)