heatmap-generation / openvino_sample.py
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# SPDX-License-Identifier: MIT
# Copyright (C) Intel Corporation
#
# Heatmap Generation: OpenVINO Runtime sample.
# See README.md for prerequisites and inputs. Run: python3 openvino_sample.py
import cv2
import numpy as np
import openvino as ov
CONF_THRESHOLD = 0.4
# Select the model: "yolo26n" (default) or "detr-resnet-50".
MODEL = "yolo26n"
INPUT_SIZE = 800 if MODEL.startswith("detr") else 640
HEATMAP_ALPHA = 0.55
MATCH_DIST = 80.0 # max px between frames to treat detections as the same object
MAX_SPEED = 20.0 # px/frame that maps to full red
def render_speed_heatmap(frame, speed_sum, count, alpha):
"""Color traffic by average speed: blue = slow, yellow = medium,
red = fast. Only regions where vehicles were seen are tinted, so
empty background keeps its original color."""
avg = np.zeros_like(speed_sum)
seen = count > 0
avg[seen] = speed_sum[seen] / count[seen]
avg = cv2.GaussianBlur(avg, (0, 0), sigmaX=15)
presence = cv2.GaussianBlur(seen.astype(np.float32), (0, 0), sigmaX=15)
norm = np.clip(avg / MAX_SPEED, 0, 1) # 0 = slow (blue), 1 = fast (red)
color = cv2.applyColorMap((norm * 255).astype(np.uint8), cv2.COLORMAP_JET)
weight = (np.clip(presence, 0, 1) * alpha)[..., np.newaxis]
overlay = frame.astype(np.float32) * (1 - weight) + color.astype(np.float32) * weight
return overlay.astype(np.uint8), color
core = ov.Core()
model = core.read_model(f"{MODEL}_openvino_model/{MODEL}.xml")
# Change device to "GPU" or "NPU" to run on integrated GPU or NPU.
compiled = core.compile_model(model, "CPU")
cap = cv2.VideoCapture("test_video.mp4")
fps = cap.get(cv2.CAP_PROP_FPS) or 30.0
width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))
writer = cv2.VideoWriter(
"output_openvino.mp4", cv2.VideoWriter_fourcc(*"mp4v"), fps, (width, height))
speed_sum = np.zeros((height, width), dtype=np.float32)
count = np.zeros((height, width), dtype=np.float32)
prev_centroids = []
heatmap_color = None
frame_idx = 0
total_dets = 0
while True:
ok, frame = cap.read()
if not ok:
break
frame_idx += 1
h0, w0 = frame.shape[:2]
sx, sy = w0 / INPUT_SIZE, h0 / INPUT_SIZE
blob = cv2.resize(frame, (INPUT_SIZE, INPUT_SIZE))
blob = cv2.cvtColor(blob, cv2.COLOR_BGR2RGB).astype(np.float32) / 255.0
blob = blob.transpose(2, 0, 1)[np.newaxis, ...]
output = compiled([blob])[compiled.output(0)][0]
dets = output[output[:, 4] >= CONF_THRESHOLD]
total_dets += len(dets)
cur_centroids = []
for det in dets:
x1, y1 = int(det[0] * sx), int(det[1] * sy)
x2, y2 = int(det[2] * sx), int(det[3] * sy)
x1, x2 = max(0, x1), min(width, x2)
y1, y2 = max(0, y1), min(height, y2)
cx, cy = (x1 + x2) / 2, (y1 + y2) / 2
cur_centroids.append((cx, cy))
# Speed = displacement from the nearest detection in the previous frame.
speed = 0.0
if prev_centroids:
d = min(np.hypot(cx - px, cy - py) for px, py in prev_centroids)
if d <= MATCH_DIST:
speed = d
speed_sum[y1:y2, x1:x2] += speed
count[y1:y2, x1:x2] += 1.0
prev_centroids = cur_centroids
overlay, heatmap_color = render_speed_heatmap(frame, speed_sum, count, HEATMAP_ALPHA)
cv2.putText(overlay, f"Detections: {len(dets)}", (10, 30),
cv2.FONT_HERSHEY_SIMPLEX, 0.8, (255, 255, 255), 2)
writer.write(overlay)
cap.release()
writer.release()
if heatmap_color is not None:
cv2.imwrite("heatmap.jpg", heatmap_color)
print("Saved: heatmap.jpg")
print(f"Processed {frame_idx} frames, {total_dets} total detections", flush=True)