Hi everyone,
I’d like to share a Python script that saves a lot of time when creating knob filmstrips for HISE.
Instead of rotating a knob image manually frame by frame, this script:
Takes one knob image
Automatically detects the visible (non-transparent) area
Crops and centers it perfectly
Rotates it smoothly
Exports a 128-frame sprite sheet (no jitter, no wobble)
Features
- True center rotation (no shaking)
- list itemAutomatic alpha-based cropping
- list item 128 frames (super smooth)
- list item Vertical or horizontal filmstrip
- list item Ready to use in HISE
- list item Huge time saver
Requirements :
pip install pillow numpy
Full Python Code : 
️
from PIL import Image
import numpy as np
import os
# === Settings ===
image_path = "PATH/TO/KNOB.png"
output_image = "PATH/TO/KNOB_128fps.png"
num_frames = 128
start_angle = 150
end_angle = -150
orientation = "vertical" # "vertical" or "horizontal"
# === Load image ===
img = Image.open(image_path).convert("RGBA")
w, h = img.size
# === Detect non-transparent area ===
alpha = np.array(img.split()[-1])
ys, xs = np.nonzero(alpha > 0)
x_min, x_max = xs.min(), xs.max()
y_min, y_max = ys.min(), ys.max()
# === Crop to real knob area ===
img = img.crop((x_min, y_min, x_max, y_max))
w, h = img.size
# === Make square canvas for perfect rotation ===
side = max(w, h)
square = Image.new("RGBA", (side, side), (0, 0, 0, 0))
offset = ((side - w) // 2, (side - h) // 2)
square.paste(img, offset)
img = square
w = h = side
# === Lock rotation center ===
cx, cy = w / 2, h / 2
print(f"Rotation center locked at ({cx}, {cy})")
# === Create sprite sheet ===
if orientation == "horizontal":
sprite = Image.new("RGBA", (w * num_frames, h), (0, 0, 0, 0))
else:
sprite = Image.new("RGBA", (w, h * num_frames), (0, 0, 0, 0))
# === Generate frames ===
for i in range(num_frames):
angle = start_angle + (end_angle - start_angle) * (i / (num_frames - 1))
rotated = img.rotate(angle, resample=Image.BICUBIC, center=(cx, cy))
if orientation == "horizontal":
sprite.paste(rotated, (i * w, 0))
else:
sprite.paste(rotated, (0, i * h))
sprite.save(output_image)
print(f"Sprite generated successfully: {output_image}")
Save the file with this name : ️
generate_knob_sprite.py
Make sure the file extension is .py and not .txt.
Open Command Prompt / PowerShell & Run the script ️
python .\generate_knob_sprite.py
Good luck
