Merge pull request #3071 from adafruit/thermal_pi
adding raspberry pi thermal camera code
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Liz
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Raspberry_Pi_Thermal_Camera_Overlay/code.py
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Raspberry_Pi_Thermal_Camera_Overlay/code.py
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# SPDX-FileCopyrightText: 2025 Liz Clark for Adafruit Industries
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#
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# SPDX-License-Identifier: MIT
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"""
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Thermal Camera Overlay for Raspberry Pi 4,
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PiCamera 3 and STEMMA MLX90640
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Inspired by PitFusion Thermal Imager
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"""
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import time
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import numpy as np
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import cv2
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import board
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import busio
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import adafruit_mlx90640
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from picamera2 import Picamera2
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from PIL import Image
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# Temperature range for thermal camera (in Celsius)
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MIN_TEMP = 20.0
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MAX_TEMP = 35.0
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# Thermal overlay opacity (0.0 = invisible, 1.0 = fully opaque)
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THERMAL_OPACITY = 0.7
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# Display window size
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WINDOW_WIDTH = 1280
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WINDOW_HEIGHT = 720
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# Camera settings
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CAMERA_WIDTH = 1280
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CAMERA_HEIGHT = 720
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SKIP_FRAMES = 2 # Process every Nth frame for thermal
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frame_counter = 0
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# Thermal camera size
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THERMAL_WIDTH = 32
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THERMAL_HEIGHT = 24
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# Thermal zoom factor (1.7x to compensate for FoV difference)
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# Thermal camera FoV: 110°x75°, Pi camera FoV: 66°x41°
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# Ratio: 66/110 = 0.6, so we need 1/0.6 = 1.67x zoom
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THERMAL_ZOOM = 1.7
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# Camera crop settings to compensate for thermal offset
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# This crops the camera image to match the thermal coverage area
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CAMERA_CROP_LEFT = 65 # Match thermal X offset
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CAMERA_CROP_TOP = 85 # Match thermal Y offset
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CAMERA_CROP_RIGHT = 0 # No crop on right
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CAMERA_CROP_BOTTOM = 0 # No crop on bottom
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# Calculate effective camera size after cropping
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CAMERA_CROP_WIDTH = CAMERA_WIDTH - CAMERA_CROP_LEFT - CAMERA_CROP_RIGHT
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CAMERA_CROP_HEIGHT = CAMERA_HEIGHT - CAMERA_CROP_TOP - CAMERA_CROP_BOTTOM
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# ============= SETUP THERMAL CAMERA =============
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print("Setting up thermal camera...")
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i2c = busio.I2C(board.SCL, board.SDA)
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mlx = adafruit_mlx90640.MLX90640(i2c)
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mlx.refresh_rate = adafruit_mlx90640.RefreshRate.REFRESH_4_HZ
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# Create array to hold thermal data
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thermal_frame = np.zeros(768, dtype=np.float32)
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# ============= SETUP REGULAR CAMERA =============
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print("Setting up Pi camera...")
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picam2 = Picamera2()
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camera_config = picam2.create_preview_configuration(
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main={"size": (CAMERA_WIDTH, CAMERA_HEIGHT), "format": "RGB888"},
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buffer_count=2, # Reduce buffer count for lower latency
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queue=False # Don't queue frames
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)
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picam2.configure(camera_config)
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picam2.start()
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picam2.set_controls({"ExposureTime": 20000, "AnalogueGain": 1.0})
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time.sleep(2)
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# ============= CREATE THERMAL COLORMAP =============
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def create_thermal_colormap():
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"""Create a colormap for thermal visualization"""
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# Define color points (blue -> cyan -> green -> yellow -> orange -> red)
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colors = np.array([
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[0, 0, 64], # Dark blue (cold)
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[0, 0, 255], # Blue
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[0, 255, 255], # Cyan
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[0, 255, 0], # Green
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[255, 255, 0], # Yellow
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[255, 128, 0], # Orange
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[255, 0, 0], # Red (hot)
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], dtype=np.uint8)
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# Create smooth gradient between colors
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colormap = np.zeros((256, 3), dtype=np.uint8)
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positions = np.linspace(0, len(colors)-1, 256)
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for i in range(256):
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pos = positions[i]
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idx = int(pos)
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frac = pos - idx
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if idx >= len(colors) - 1:
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colormap[i] = colors[-1]
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else:
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colormap[i] = (1 - frac) * colors[idx] + frac * colors[idx + 1]
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colormap = colormap[::-1] # Reverse the colormap
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return colormap
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the_colormap = create_thermal_colormap()
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# ============= HELPER FUNCTIONS =============
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def process_thermal_frame(thermal_data, colormap):
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"""Convert thermal data to colored image"""
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# Calculate temperature statistics
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min_temp = np.min(thermal_data)
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max_temp = np.max(thermal_data)
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avg_temp = np.mean(thermal_data)
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if min_temp < -100:
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min_temp = MIN_TEMP
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avg_temp = (MIN_TEMP + MAX_TEMP) / 2
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# Normalize temperature data to 0-255 range
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normalized = np.clip(
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(thermal_data - MIN_TEMP) / (MAX_TEMP - MIN_TEMP) * 255,
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0, 255
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).astype(np.uint8)
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# Apply colormap
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colored = colormap[normalized]
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# Reshape to 2D image (24x32x3)
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thermal_image = colored.reshape(THERMAL_HEIGHT, THERMAL_WIDTH, 3)
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# Flip horizontally to match camera view
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thermal_image = np.fliplr(thermal_image)
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# Scale up to camera size using PIL for smooth interpolation
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pil_thermal = Image.fromarray(thermal_image)
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# Apply zoom by scaling to a larger size than the camera
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scaled_width = int(CAMERA_WIDTH * THERMAL_ZOOM)
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scaled_height = int(CAMERA_HEIGHT * THERMAL_ZOOM)
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pil_thermal = pil_thermal.resize((scaled_width, scaled_height), Image.BICUBIC)
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# Crop the center to match camera size (this creates the zoom effect)
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thermal_array = np.array(pil_thermal)
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crop_x = (scaled_width - CAMERA_WIDTH) // 2
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crop_y = (scaled_height - CAMERA_HEIGHT) // 2
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thermal_cropped = thermal_array[crop_y:crop_y+CAMERA_HEIGHT, crop_x:crop_x+CAMERA_WIDTH]
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return thermal_cropped, min_temp, max_temp, avg_temp
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def blend_images(camera_image, thermal_image, opacity):
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"""Blend camera and thermal images with position offset"""
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# Create a canvas the same size as the camera image
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canvas = camera_image.copy()
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# Calculate position with offset
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x_offset = 0
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y_offset = 0
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# Ensure the thermal image fits within bounds
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x_start = max(0, x_offset)
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y_start = max(0, y_offset)
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x_end = min(camera_image.shape[1], x_offset + thermal_image.shape[1])
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y_end = min(camera_image.shape[0], y_offset + thermal_image.shape[0])
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# Calculate the corresponding region in the thermal image
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thermal_x_start = max(0, -x_offset)
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thermal_y_start = max(0, -y_offset)
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thermal_x_end = thermal_x_start + (x_end - x_start)
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thermal_y_end = thermal_y_start + (y_end - y_start)
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# Blend only the overlapping region
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if x_end > x_start and y_end > y_start:
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canvas[y_start:y_end, x_start:x_end] = (
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canvas[y_start:y_end, x_start:x_end] * (1 - opacity) +
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thermal_image[thermal_y_start:thermal_y_end, thermal_x_start:thermal_x_end] * opacity
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)
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return canvas.astype(np.uint8)
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def add_temperature_scale(image, colormap):
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"""Add temperature scale bar to the image"""
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# Create scale bar
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scale_height = 20
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scale_width = 200
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scale_x = image.shape[1] - scale_width - 20
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scale_y = 90 # Moved down to make room for buttons
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# Draw temperature gradient
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for i in range(scale_width):
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temp_normalized = i / scale_width
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color_idx = int(temp_normalized * 255)
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color = colormap[color_idx]
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cv2.line(image,
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(scale_x + i, scale_y),
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(scale_x + i, scale_y + scale_height),
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color.tolist(), 1)
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# Add temperature labels
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cv2.putText(image, f"{MIN_TEMP:.0f}C",
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(scale_x - 35, scale_y + 15),
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cv2.FONT_HERSHEY_SIMPLEX, 0.5, (255, 255, 255), 1)
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cv2.putText(image, f"{MAX_TEMP:.0f}C",
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(scale_x + scale_width + 5, scale_y + 15),
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cv2.FONT_HERSHEY_SIMPLEX, 0.5, (255, 255, 255), 1)
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# Draw border around scale
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cv2.rectangle(image,
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(scale_x - 1, scale_y - 1),
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(scale_x + scale_width + 1, scale_y + scale_height + 1),
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(255, 255, 255), 1)
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# ============= MAIN LOOP =============
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print("Starting thermal camera overlay...")
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print("Use Up/Down keys to increase/decrease max temp")
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print("Use Left/Right keys to increase/decrease min temp")
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print("Use +/- keys to increase/decrease overlay opacity")
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print("Use Q key to exit")
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cv2.namedWindow('Thermal Overlay', cv2.WINDOW_NORMAL)
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cv2.resizeWindow('Thermal Overlay', WINDOW_WIDTH, WINDOW_HEIGHT)
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# Temperature statistics
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temp_stats = {"min": 0, "max": 0, "avg": 0}
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last_thermal_colored = None
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try:
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while True:
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# Read thermal data (only every SKIP_FRAMES frames)
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if frame_counter % SKIP_FRAMES == 0:
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try:
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mlx.getFrame(thermal_frame)
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# Process thermal data to colored image
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last_thermal_colored, temp_stats["min"], temp_stats["max"], temp_stats["avg"] = process_thermal_frame(thermal_frame, the_colormap) # pylint: disable=line-too-long
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except Exception as e: # pylint: disable=broad-except
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print(f"Thermal read error: {e}")
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frame_counter += 1
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# Use the last processed thermal frame
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if last_thermal_colored is not None:
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thermal_colored = last_thermal_colored
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else:
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# Create a blank thermal image if we don't have one yet
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thermal_colored = np.zeros((CAMERA_HEIGHT, CAMERA_WIDTH, 3), dtype=np.uint8)
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# Capture camera frame
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camera_frame = picam2.capture_array()
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# Crop the camera frame to match thermal coverage area
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camera_cropped = camera_frame[
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CAMERA_CROP_TOP:CAMERA_HEIGHT-CAMERA_CROP_BOTTOM,
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CAMERA_CROP_LEFT:CAMERA_WIDTH-CAMERA_CROP_RIGHT
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]
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# Resize cropped camera back to full display size
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camera_resized = cv2.resize(camera_cropped, (CAMERA_WIDTH, CAMERA_HEIGHT),
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interpolation=cv2.INTER_LINEAR)
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# Blend camera and thermal images (now both are aligned)
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overlay_image = blend_images(camera_resized, thermal_colored, THERMAL_OPACITY)
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# Add temperature scale
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add_temperature_scale(overlay_image, the_colormap)
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# Add status text with temperature statistics and FPS
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status_text = f"Range: {MIN_TEMP:.0f}-{MAX_TEMP:.0f}C | Opacity: {THERMAL_OPACITY:.1f} | "
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status_text += f"Min: {temp_stats['min']:.1f}C | Max: {temp_stats['max']:.1f}C | Avg: {temp_stats['avg']:.1f}C | " # pylint: disable=line-too-long
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cv2.putText(overlay_image, status_text,
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(10, overlay_image.shape[0] - 10),
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cv2.FONT_HERSHEY_SIMPLEX, 0.6, (255, 255, 255), 2)
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# Display the image
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cv2.imshow('Thermal Overlay', overlay_image)
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# Check if window was closed
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if cv2.getWindowProperty('Thermal Overlay', cv2.WND_PROP_VISIBLE) < 1:
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break
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key_action = cv2.waitKey(1) & 0xFF
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if key_action == ord('q'):
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raise KeyboardInterrupt
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if key_action == 82:
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MAX_TEMP = min(MAX_TEMP + 1, 100)
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print(f"Max temp: {MAX_TEMP:.1f}C")
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elif key_action == 84:
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MAX_TEMP = max(MAX_TEMP - 1, MIN_TEMP + 1)
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print(f"Max temp: {MAX_TEMP:.1f}C")
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elif key_action == 81:
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MIN_TEMP = max(MIN_TEMP - 1, -20)
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print(f"Min temp: {MIN_TEMP:.1f}C")
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elif key_action == 83:
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MIN_TEMP = min(MIN_TEMP + 1, MAX_TEMP - 1)
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print(f"Min temp: {MIN_TEMP:.1f}C")
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elif key_action == ord('+'):
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THERMAL_OPACITY = min(THERMAL_OPACITY + 0.1, 1.0)
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print(f"Opacity: {THERMAL_OPACITY:.1f}")
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elif key_action == ord('-'):
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THERMAL_OPACITY = max(THERMAL_OPACITY - 0.1, 0.0)
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print(f"Opacity: {THERMAL_OPACITY:.1f}")
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elif key_action == ord('z'):
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THERMAL_OPACITY = not THERMAL_OPACITY
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print(f"Opacity: {THERMAL_OPACITY:.1f}")
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except KeyboardInterrupt:
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print("\nShutting down...")
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finally:
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print("Cleaning up...")
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cv2.destroyAllWindows()
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cv2.waitKey(1)
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picam2.stop()
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