pulse-monitor/detection.go

package main

import (
	"fmt"
	"image"
	"image/color"
	"math"
	"sort"

	"gocv.io/x/gocv"
)

// DEBUG flag is declared in types.go

// Band represents a vertical band of contours
type Band struct {
	minX int
	maxX int
	minY int
	maxY int
}

// DetectBands finds and groups contours into vertical bands
// Only returns bands with height >= minHeight pixels
func DetectBands(binary gocv.Mat, minHeight int) []Band {
	type Box struct {
		minX int
		maxX int
		minY int
		maxY int
	}

	// Remove thin vertical lines (UI borders) using morphological opening with horizontal kernel
	// This breaks the connection between rows caused by vertical UI elements
	kernel := gocv.GetStructuringElement(gocv.MorphRect, image.Pt(15, 1)) // Wide horizontal kernel
	cleaned := gocv.NewMat()
	gocv.MorphologyEx(binary, &cleaned, gocv.MorphOpen, kernel)
	kernel.Close()
	defer cleaned.Close()

	// Find contours on the cleaned image
	contours := gocv.FindContours(cleaned, gocv.RetrievalExternal, gocv.ChainApproxSimple)

	// Get all bounding boxes, filtering out tall thin UI elements (borders)
	boxes := []Box{}
	frameHeight := binary.Rows()
	for i := 0; i < contours.Size(); i++ {
		rect := gocv.BoundingRect(contours.At(i))
		width := rect.Max.X - rect.Min.X
		height := rect.Max.Y - rect.Min.Y

		// Skip tall thin contours (aspect ratio > 8) that span most of frame height
		// These are likely UI borders, not content
		if width > 0 && height > frameHeight*6/10 {
			aspectRatio := float64(height) / float64(width)
			if aspectRatio > 8 {
				if DEBUG {
					fmt.Printf("DEBUG: Skipping border contour: %dx%d (aspect=%.1f)\n", width, height, aspectRatio)
				}
				continue
			}
		}

		boxes = append(boxes, Box{
			minX: rect.Min.X,
			maxX: rect.Max.X,
			minY: rect.Min.Y,
			maxY: rect.Max.Y,
		})
	}

	// Sort boxes by minY
	sort.Slice(boxes, func(i, j int) bool {
		return boxes[i].minY < boxes[j].minY
	})

	// Group overlapping/adjacent boxes into vertical bands
	bands := []Band{}

	for _, box := range boxes {
		// Skip boxes shorter than minHeight
		height := box.maxY - box.minY
		if height < minHeight {
			continue
		}

		if len(bands) == 0 {
			// First band
			bands = append(bands, Band{
				minX: box.minX,
				maxX: box.maxX,
				minY: box.minY,
				maxY: box.maxY,
			})
		} else {
			lastBand := &bands[len(bands)-1]

			// Check if this box overlaps or is close to last band (within 5px)
			if box.minY <= lastBand.maxY+5 {
				// Merge: extend the band in both X and Y
				if box.minX < lastBand.minX {
					lastBand.minX = box.minX
				}
				if box.maxX > lastBand.maxX {
					lastBand.maxX = box.maxX
				}
				if box.maxY > lastBand.maxY {
					lastBand.maxY = box.maxY
				}
			} else {
				// New band
				bands = append(bands, Band{
					minX: box.minX,
					maxX: box.maxX,
					minY: box.minY,
					maxY: box.maxY,
				})
			}
		}
	}

	return bands
}

// findBaseline analyzes the baseline in the graph band
// Returns left point, right point, width, number of sections, and error
func findBaseline(binary gocv.Mat, graphBand Band) (*image.Point, *image.Point, int, int, error) {
	// Extract just the graph band region
	graphRegion := binary.Region(image.Rect(0, graphBand.minY, binary.Cols(), graphBand.maxY+1))

	// Find all contours in graph region
	contours := gocv.FindContours(graphRegion, gocv.RetrievalExternal, gocv.ChainApproxSimple)

	// Get sections (contours) with width >= 5px
	type Section struct {
		minX int
		maxX int
		minY int
		maxY int
		width int
		height int
	}
	sections := []Section{}
	allContours := []Section{}  // For debug visualization

	for i := 0; i < contours.Size(); i++ {
		rect := gocv.BoundingRect(contours.At(i))
		width := rect.Max.X - rect.Min.X
		height := rect.Max.Y - rect.Min.Y
		
		// Collect ALL contours >= 50px high for visualization
		if height >= 50 {
			allContours = append(allContours, Section{
				minX: rect.Min.X,
				maxX: rect.Max.X,
				minY: rect.Min.Y + graphBand.minY,
				maxY: rect.Max.Y + graphBand.minY,
				width: width,
				height: height,
			})
		}
		
		// Filter: width >= 5px AND height >= 50px for baseline detection
		// (lowered from 80px to handle smaller waveform sections)
		if width >= 5 && height >= 50 {
			sections = append(sections, Section{
				minX: rect.Min.X,
				maxX: rect.Max.X,
				minY: rect.Min.Y + graphBand.minY, // Adjust to full image coordinates
				maxY: rect.Max.Y + graphBand.minY,
				width: width,
				height: height,
			})
		}
	}
	
	// DEBUG: Visualize ALL contours >= 50px high
	if DEBUG {
		viz := gocv.NewMat()
		gocv.CvtColor(binary, &viz, gocv.ColorGrayToBGR)
		
		// Draw graph band boundaries
		gocv.Line(&viz, image.Pt(0, graphBand.minY), image.Pt(viz.Cols(), graphBand.minY),
			color.RGBA{255, 0, 255, 255}, 2)
		gocv.Line(&viz, image.Pt(0, graphBand.maxY), image.Pt(viz.Cols(), graphBand.maxY),
			color.RGBA{255, 0, 255, 255}, 2)
		
		// Draw ALL contours >= 50px high in yellow
		for i, c := range allContours {
			rect := image.Rect(c.minX, c.minY, c.maxX, c.maxY)
			gocv.Rectangle(&viz, rect, color.RGBA{0, 255, 255, 255}, 2)
			label := fmt.Sprintf("#%d: %dx%d", i+1, c.width, c.height)
			gocv.PutText(&viz, label, image.Pt(c.minX, c.minY-5),
				gocv.FontHersheyPlain, 1.0, color.RGBA{0, 255, 255, 255}, 1)
		}
		
		// Highlight sections that passed the 80px height filter in green
		for i, s := range sections {
			rect := image.Rect(s.minX, s.minY, s.maxX, s.maxY)
			gocv.Rectangle(&viz, rect, color.RGBA{0, 255, 0, 255}, 3)
			label := fmt.Sprintf("BASELINE#%d", i+1)
			gocv.PutText(&viz, label, image.Pt(s.minX, s.maxY+20),
				gocv.FontHersheyPlain, 1.2, color.RGBA{0, 255, 0, 255}, 2)
		}
		
		// Add summary text
		summary := fmt.Sprintf("Contours H>=50px: %d | Baseline sections: %d", len(allContours), len(sections))
		gocv.PutText(&viz, summary, image.Pt(10, 30),
			gocv.FontHersheyDuplex, 1.0, color.RGBA{255, 255, 0, 255}, 2)
		
		gocv.IMWrite("test_output/debug_all_contours.png", viz)
		viz.Close()
		fmt.Println("💾 Saved all contours visualization to test_output/debug_all_contours.png")
	}

	// Check if we have exactly 2 sections
	if len(sections) != 2 {
		return nil, nil, 0, len(sections), fmt.Errorf("found %d sections (need exactly 2)", len(sections))
	}

	// Sort sections by X position (left to right)
	sort.Slice(sections, func(i, j int) bool {
		return sections[i].minX < sections[j].minX
	})

	// Horizontal width (left edge of left section to right edge of right section)
	horizontalWidth := sections[1].maxX - sections[0].minX

	// Fixed offset from edges for sampling points
	// Needs to be large enough to avoid curved edges due to tilt
	offset := 10

	// Find rotation points
	// Left section: lowest white pixel offset from left edge
	leftSection := sections[0]
	leftX := leftSection.minX + offset
	leftPoint := findLowestWhitePixel(binary, leftX, graphBand.minY, graphBand.maxY)

	// Right section: lowest white pixel offset from right edge
	rightSection := sections[1]
	rightX := rightSection.maxX - offset
	rightPoint := findLowestWhitePixel(binary, rightX, graphBand.minY, graphBand.maxY)

	if leftPoint == nil || rightPoint == nil {
		return nil, nil, 0, len(sections), fmt.Errorf("could not find rotation endpoints")
	}

	return leftPoint, rightPoint, horizontalWidth, len(sections), nil
}

// findLowestWhitePixel finds the lowest (max Y) white pixel at given X within Y range
func findLowestWhitePixel(binary gocv.Mat, x int, minY int, maxY int) *image.Point {
	lowestY := -1
	for y := minY; y <= maxY; y++ {
		if binary.GetUCharAt(y, x) == 255 {
			lowestY = y
		}
	}
	if lowestY == -1 {
		return nil
	}
	return &image.Point{X: x, Y: lowestY}
}

// DetectionResult contains rotation and width detection results
type DetectionResult struct {
	Rotation    float64
	Width       int
	ScaleFactor float64         // Scale factor to apply (860 / width)
	SpO2        image.Rectangle // SpO2 display area in SCALED, ROTATED coordinates
	HR          image.Rectangle // HR display area in SCALED, ROTATED coordinates
	Success     bool
}

// PreprocessFrame takes a raw frame and prepares it for detection
// Returns the processed binary image
func PreprocessFrame(frame gocv.Mat) gocv.Mat {
	// Crop top 68 pixels (timestamp)
	cropped := frame.Region(image.Rect(0, 68, frame.Cols(), frame.Rows()))

	// Rotate 90° clockwise
	rotated := gocv.NewMat()
	gocv.Rotate(cropped, &rotated, gocv.Rotate90Clockwise)

	// Convert to grayscale
	gray := gocv.NewMat()
	gocv.CvtColor(rotated, &gray, gocv.ColorBGRToGray)
	rotated.Close()

	// Threshold to binary (matching main pipeline)
	binary := gocv.NewMat()
	gocv.Threshold(gray, &binary, 180, 255, gocv.ThresholdBinary)
	gray.Close()

	return binary
}

// DetectRotationAndWidth analyzes a binary frame and returns rotation angle, width, and display areas
// Works on its own internal copy - does NOT modify the input frame
// Returns coordinates in TRANSFORMED (scaled to 860px, rotated) coordinate space
func DetectRotationAndWidth(binary gocv.Mat) DetectionResult {
	// Clone the input so we don't modify it
	workingCopy := binary.Clone()
	defer workingCopy.Close()

	// ========== PHASE 1: Detect rotation & scale from baseline ==========

	// Detect bands (using 40px minimum height for original scale - lowered for stream2 which is lower res)
	bands := DetectBands(workingCopy, 40)

	// Save debug image showing detected bands (only in DEBUG mode)
	if DEBUG {
		viz := gocv.NewMat()
		gocv.CvtColor(workingCopy, &viz, gocv.ColorGrayToBGR)
		colors := []color.RGBA{
			{255, 0, 0, 0},     // Red
			{0, 255, 0, 0},     // Green
			{0, 0, 255, 0},     // Blue
			{255, 255, 0, 0},   // Yellow
			{255, 0, 255, 0},   // Magenta
			{0, 255, 255, 0},   // Cyan
		}
		for i, band := range bands {
			c := colors[i%len(colors)]
			gocv.Rectangle(&viz, image.Rect(band.minX, band.minY, band.maxX, band.maxY), c, 2)
			gocv.PutText(&viz, fmt.Sprintf("Band %d: h=%d", i, band.maxY-band.minY),
				image.Pt(band.minX, band.minY-5), gocv.FontHersheyPlain, 1.0, c, 1)
		}
		gocv.PutText(&viz, fmt.Sprintf("Total bands: %d (need >=2)", len(bands)),
			image.Pt(10, 30), gocv.FontHersheyPlain, 1.5, color.RGBA{255, 255, 255, 0}, 2)
		gocv.IMWrite("test_output/debug_bands.png", viz)
		viz.Close()
	}

	// Check if we have any content visible
	if len(bands) < 1 {
		if DEBUG {
			fmt.Printf("DEBUG: Detection failed - no bands found\n")
		}
		return DetectionResult{Success: false}
	}

	// For rotation detection, we ideally want a waveform band
	// If available, use band 0 as graph band; otherwise skip rotation detection
	var graphBand Band
	var hasGraphBand bool
	if len(bands) >= 1 {
		graphBand = bands[0] // Use first band for rotation detection if available
		hasGraphBand = true
		if DEBUG {
			fmt.Printf("DEBUG: Using band 0 as graph band (h=%d)\n", graphBand.maxY-graphBand.minY)
		}
	}

	// Find baseline for rotation detection (only if we have a usable graph band)
	var leftPoint, rightPoint *image.Point
	var width, sections int
	var err error

	if hasGraphBand {
		leftPoint, rightPoint, width, sections, err = findBaseline(workingCopy, graphBand)
	}

	// Variables for rotation and scale
	var rotation float64
	var scaleFactor float64

	if !hasGraphBand || err != nil || sections != 2 {
		// Baseline detection failed or not available - use fallback (assume no rotation, scale=1)
		if DEBUG {
			if !hasGraphBand {
				fmt.Printf("DEBUG: No graph band - using fallback rotation=0, scale=1\n")
			} else if err != nil {
				fmt.Printf("DEBUG: Baseline failed (%v) - using fallback\n", err)
			} else {
				fmt.Printf("DEBUG: Baseline found %d sections - using fallback\n", sections)
			}
		}
		rotation = 0.0
		scaleFactor = 1.0  // No scaling for fixed layout approach
		width = workingCopy.Cols()
		// Create dummy points for visualization
		midY := workingCopy.Rows() / 2
		leftPoint = &image.Point{X: 0, Y: midY}
		rightPoint = &image.Point{X: workingCopy.Cols(), Y: midY}
	} else {
		// Baseline detection succeeded - calculate rotation and scale
		deltaY := float64(rightPoint.Y - leftPoint.Y)
		deltaX := float64(rightPoint.X - leftPoint.X)
		rotation = math.Atan2(deltaY, deltaX) * 180 / math.Pi
		scaleFactor = 860.0 / float64(width)
	}

	// DEBUG: Visualize the baseline points
	if DEBUG {
		viz := gocv.NewMat()
		gocv.CvtColor(workingCopy, &viz, gocv.ColorGrayToBGR)
		
		// Find the two baseline sections for visualization
		graphRegion := workingCopy.Region(image.Rect(0, graphBand.minY, workingCopy.Cols(), graphBand.maxY+1))
		contours := gocv.FindContours(graphRegion, gocv.RetrievalExternal, gocv.ChainApproxSimple)
		
		type Section struct {
			minX int
			maxX int
			minY int
			maxY int
		}
		sections := []Section{}
		
		for i := 0; i < contours.Size(); i++ {
			rect := gocv.BoundingRect(contours.At(i))
			width := rect.Max.X - rect.Min.X
			height := rect.Max.Y - rect.Min.Y
			if width >= 5 && height >= 80 {
				sections = append(sections, Section{
					minX: rect.Min.X,
					maxX: rect.Max.X,
					minY: rect.Min.Y + graphBand.minY,
					maxY: rect.Max.Y + graphBand.minY,
				})
			}
		}
		
		sort.Slice(sections, func(i, j int) bool {
			return sections[i].minX < sections[j].minX
		})
		
		// Draw baseline sections in cyan
		for i, sec := range sections {
			rect := image.Rect(sec.minX, sec.minY, sec.maxX, sec.maxY)
			gocv.Rectangle(&viz, rect, color.RGBA{0, 255, 255, 255}, 2)
			label := fmt.Sprintf("Sec%d: %dpx", i+1, sec.maxX-sec.minX)
			gocv.PutText(&viz, label, image.Pt(sec.minX, sec.minY-5),
				gocv.FontHersheyPlain, 1.0, color.RGBA{0, 255, 255, 255}, 1)
		}
		
		// Draw left point (green circle)
		gocv.Circle(&viz, *leftPoint, 10, color.RGBA{0, 255, 0, 255}, -1)
		gocv.PutText(&viz, "L", image.Pt(leftPoint.X-5, leftPoint.Y-15),
			gocv.FontHersheyPlain, 1.5, color.RGBA{0, 255, 0, 255}, 2)
		
		// Draw right point (red circle)
		gocv.Circle(&viz, *rightPoint, 10, color.RGBA{0, 0, 255, 255}, -1)
		gocv.PutText(&viz, "R", image.Pt(rightPoint.X-5, rightPoint.Y-15),
			gocv.FontHersheyPlain, 1.5, color.RGBA{0, 0, 255, 255}, 2)
		
		// Draw line between baseline points (yellow)
		gocv.Line(&viz, *leftPoint, *rightPoint, color.RGBA{0, 255, 255, 255}, 3)
		
		// Draw graph band boundaries (magenta)
		gocv.Line(&viz, image.Pt(0, graphBand.minY), image.Pt(viz.Cols(), graphBand.minY), color.RGBA{255, 0, 255, 255}, 2)
		gocv.Line(&viz, image.Pt(0, graphBand.maxY), image.Pt(viz.Cols(), graphBand.maxY), color.RGBA{255, 0, 255, 255}, 2)
		gocv.PutText(&viz, "Graph Band", image.Pt(10, graphBand.minY+20),
			gocv.FontHersheyPlain, 1.2, color.RGBA{255, 0, 255, 255}, 1)
		
		// Add measurements text overlay at top
		widthText := fmt.Sprintf("Baseline Width: %dpx", width)
		gocv.PutText(&viz, widthText, image.Pt(10, 30),
			gocv.FontHersheyDuplex, 1.0, color.RGBA{255, 255, 0, 255}, 2)
		
		rotText := fmt.Sprintf("Rotation: %.3f deg", rotation)
		gocv.PutText(&viz, rotText, image.Pt(10, 60),
			gocv.FontHersheyDuplex, 1.0, color.RGBA{255, 255, 0, 255}, 2)
		
		scaleText := fmt.Sprintf("Scale: %.3f (->860px)", scaleFactor)
		gocv.PutText(&viz, scaleText, image.Pt(10, 90),
			gocv.FontHersheyDuplex, 1.0, color.RGBA{255, 255, 0, 255}, 2)
		
		gocv.IMWrite("test_output/debug_baseline_detection.png", viz)
		viz.Close()
		fmt.Println("💾 Saved baseline detection visualization to test_output/debug_baseline_detection.png")
	}
	
	if DEBUG {
		fmt.Printf("DEBUG: Baseline points: Left(%d,%d) Right(%d,%d)\n",
			leftPoint.X, leftPoint.Y, rightPoint.X, rightPoint.Y)
		fmt.Printf("DEBUG: Delta Y=%d, Delta X=%d, Rotation=%.3f°\n",
			rightPoint.Y-leftPoint.Y, rightPoint.X-leftPoint.X, rotation)
		fmt.Printf("DEBUG: Width=%dpx, Scale factor=%.3f (baseline will become 860px)\n",
			width, scaleFactor)
	}
	
	// ========== PHASE 2: Find the main digit band for SpO2/HR ==========
	//
	// For this pulse-ox display, use FIXED proportions since the layout is consistent
	// and dynamic band detection is unreliable due to vertical UI elements
	//
	// After 90° CW rotation, the frame layout is approximately:
	// - Y 0-35%: Status bar, bell icon
	// - Y 35-45%: Waveform display
	// - Y 45-60%: Main SpO2/HR digits (what we want!)
	// - Y 60-75%: Secondary readings

	frameHeight := workingCopy.Rows()
	frameWidth := workingCopy.Cols()

	// Use fixed proportions for the digit band
	digitBand := Band{
		minX: int(float64(frameWidth) * 0.05),   // Slight margin from left
		maxX: int(float64(frameWidth) * 0.75),   // Avoid the vertical progress bar on right
		minY: int(float64(frameHeight) * 0.45),
		maxY: int(float64(frameHeight) * 0.58),
	}

	if DEBUG {
		fmt.Printf("DEBUG: Using fixed digit band: Y[%d-%d], X[%d-%d] (frame %dx%d)\n",
			digitBand.minY, digitBand.maxY, digitBand.minX, digitBand.maxX,
			frameWidth, frameHeight)
	}

	// Split digit band: left half = SpO2, right half = HR
	bandWidth := digitBand.maxX - digitBand.minX
	midX := digitBand.minX + bandWidth/2

	// SpO2 is left half, HR is right half
	spo2Rect := image.Rect(
		digitBand.minX,
		digitBand.minY,
		midX,
		digitBand.maxY,
	)
	hrRect := image.Rect(
		midX,
		digitBand.minY,
		digitBand.maxX,
		digitBand.maxY,
	)

	if DEBUG {
		fmt.Printf("DEBUG: SpO2 display area: X[%d-%d] Y[%d-%d]\n",
			spo2Rect.Min.X, spo2Rect.Max.X, spo2Rect.Min.Y, spo2Rect.Max.Y)
		fmt.Printf("DEBUG: HR display area: X[%d-%d] Y[%d-%d]\n",
			hrRect.Min.X, hrRect.Max.X, hrRect.Min.Y, hrRect.Max.Y)

		// Visualize final display boxes
		viz2 := gocv.NewMat()
		gocv.CvtColor(workingCopy, &viz2, gocv.ColorGrayToBGR)

		// Draw SpO2 box in red
		gocv.Rectangle(&viz2, spo2Rect, color.RGBA{255, 0, 0, 255}, 3)
		gocv.PutText(&viz2, "SpO2", image.Pt(spo2Rect.Min.X, spo2Rect.Min.Y-10),
			gocv.FontHersheyDuplex, 1.2, color.RGBA{255, 0, 0, 255}, 2)

		// Draw HR box in cyan
		gocv.Rectangle(&viz2, hrRect, color.RGBA{0, 255, 255, 255}, 3)
		gocv.PutText(&viz2, "HR", image.Pt(hrRect.Min.X, hrRect.Min.Y-10),
			gocv.FontHersheyDuplex, 1.2, color.RGBA{0, 255, 255, 255}, 2)

		gocv.IMWrite("test_output/debug_final_boxes.png", viz2)
		viz2.Close()
		fmt.Println("💾 Saved final display boxes visualization to test_output/debug_final_boxes.png")
	}

	return DetectionResult{
		Rotation:    rotation,
		Width:       width,
		ScaleFactor: scaleFactor,
		SpO2:        spo2Rect,
		HR:          hrRect,
		Success:     true,
	}
}

// RotateImage rotates an image by the given angle in degrees
// The angle is the detected rotation that needs to be corrected
func RotateImage(img gocv.Mat, angleDegrees float64) gocv.Mat {
	// Get image center
	center := image.Point{
		X: img.Cols() / 2,
		Y: img.Rows() / 2,
	}

	// Apply rotation to correct the tilt
	// NOTE: If image rotates wrong direction, change to: -angleDegrees
	rotMat := gocv.GetRotationMatrix2D(center, angleDegrees, 1.0)
	defer rotMat.Close()

	// Apply rotation
	rotated := gocv.NewMat()
	gocv.WarpAffine(img, &rotated, rotMat, image.Point{X: img.Cols(), Y: img.Rows()})

	if DEBUG {
		fmt.Printf("DEBUG: Applied rotation: %.3f°\n", angleDegrees)
	}

	return rotated
}

// ExtractBandRegion extracts a specific band region from an image
func ExtractBandRegion(img gocv.Mat, band Band) gocv.Mat {
	// Create a region of interest (ROI) for the band
	rect := image.Rect(0, band.minY, img.Cols(), band.maxY)
	region := img.Region(rect)

	// Clone the region to create an independent Mat
	extracted := gocv.NewMat()
	region.CopyTo(&extracted)

	if DEBUG {
		fmt.Printf("DEBUG: Extracted band region [%d-%d], size: %dx%d\n",
			band.minY, band.maxY, extracted.Cols(), extracted.Rows())
	}

	return extracted
}

// FindDigitBoxes finds individual digit contours within a region
// Returns bounding rectangles for digits larger than minSize
func FindDigitBoxes(digitRegion gocv.Mat, minSize int) []image.Rectangle {
	contours := gocv.FindContours(digitRegion, gocv.RetrievalExternal, gocv.ChainApproxSimple)

	var digitBoxes []image.Rectangle
	for i := 0; i < contours.Size(); i++ {
		rect := gocv.BoundingRect(contours.At(i))
		height := rect.Max.Y - rect.Min.Y

		// Filter by minimum size - height only
		if height >= minSize {
			digitBoxes = append(digitBoxes, rect)
		}
	}

	// Sort boxes by X position (left to right)
	sort.Slice(digitBoxes, func(i, j int) bool {
		return digitBoxes[i].Min.X < digitBoxes[j].Min.X
	})

	if DEBUG {
		fmt.Printf("DEBUG: Found %d digit contours (H>=%dpx)\n", len(digitBoxes), minSize)
		
		// Visualize found boxes
		visualization := gocv.NewMat()
		defer visualization.Close()
		gocv.CvtColor(digitRegion, &visualization, gocv.ColorGrayToBGR)
		
		for i, box := range digitBoxes {
			// Draw box in green
			green := color.RGBA{0, 255, 0, 255}
			gocv.Rectangle(&visualization, box, green, 2)
			
			// Show box number and size
			label := fmt.Sprintf("#%d: %dx%d", i, box.Dx(), box.Dy())
			gocv.PutText(&visualization, label, image.Pt(box.Min.X, box.Min.Y-5),
				gocv.FontHersheyPlain, 0.8, green, 1)
		}
		
		gocv.IMWrite("test_output/debug_digit_boxes.png", visualization)
		fmt.Printf("DEBUG: Saved digit boxes to test_output/debug_digit_boxes.png\n")
	}

	return digitBoxes
}

// ScaleByFactor scales an image by a specific scale factor
func ScaleByFactor(img gocv.Mat, scaleFactor float64) gocv.Mat {
	// Calculate new dimensions
	newWidth := int(float64(img.Cols()) * scaleFactor)
	newHeight := int(float64(img.Rows()) * scaleFactor)

	// Resize image
	scaled := gocv.NewMat()
	gocv.Resize(img, &scaled, image.Point{X: newWidth, Y: newHeight}, 0, 0, gocv.InterpolationLinear)

	if DEBUG {
		fmt.Printf("DEBUG: Scaled image from %dx%d to %dx%d (scale factor: %.3f)\n",
			img.Cols(), img.Rows(), newWidth, newHeight, scaleFactor)
	}

	return scaled
}

// applyTransforms applies rotation and scaling to a frame
// This is the SINGLE source of truth for transform logic
// Both detection and main loop MUST use this function to ensure identical transforms
func applyTransforms(img gocv.Mat, rotation float64, scaleFactor float64) gocv.Mat {
	// Apply rotation (if needed)
	var rotated gocv.Mat
	if rotation != 0.0 {
		rotated = RotateImage(img, rotation)
	} else {
		rotated = img.Clone()
	}
	
	// Apply scaling (if needed)
	var scaled gocv.Mat
	if scaleFactor != 1.0 {
		scaled = ScaleByFactor(rotated, scaleFactor)
		if rotation != 0.0 {
			rotated.Close() // Only close if we created a new Mat
		}
	} else {
		scaled = rotated
	}
	
	return scaled
}

// DisplayAreas holds the two display rectangles for SpO2 and HR
type DisplayAreas struct {
	SpO2 image.Rectangle
	HR   image.Rectangle
}

// MergeDigitBoxesIntoDisplays merges individual digit boxes into two unified display areas
// This is the FINAL step of detection after finding digit boxes
// It splits at the center of the BOUNDING BOX (not image center)
// and merges all left boxes into SpO2, all right boxes into HR display area
func MergeDigitBoxesIntoDisplays(digitRegion gocv.Mat, digitBoxes []image.Rectangle) DisplayAreas {
	// First, find the bounding box of ALL digit boxes
	contentMinX := digitRegion.Cols()
	contentMaxX := 0
	for _, box := range digitBoxes {
		if box.Min.X < contentMinX {
			contentMinX = box.Min.X
		}
		if box.Max.X > contentMaxX {
			contentMaxX = box.Max.X
		}
	}

	// Calculate center of the CONTENT bounding box (not image center)
	centerX := (contentMinX + contentMaxX) / 2

	if DEBUG {
		fmt.Printf("DEBUG: Content bounding box: X[%d-%d], Center X=%d\n",
			contentMinX, contentMaxX, centerX)
	}

	// Initialize bounding boxes
	spo2MinX, spo2MaxX := digitRegion.Cols(), 0
	spo2MinY, spo2MaxY := digitRegion.Rows(), 0
	hrMinX, hrMaxX := digitRegion.Cols(), 0
	hrMinY, hrMaxY := digitRegion.Rows(), 0

	// Track counts for logging
	leftCount := 0
	rightCount := 0

	// Split boxes by center X and merge
	for _, box := range digitBoxes {
		// Calculate box center X to determine which half it's in
		boxCenterX := (box.Min.X + box.Max.X) / 2

		if boxCenterX < centerX {
			// LEFT HALF - SpO2
			leftCount++
			if box.Min.X < spo2MinX {
				spo2MinX = box.Min.X
			}
			if box.Max.X > spo2MaxX {
				spo2MaxX = box.Max.X
			}
			if box.Min.Y < spo2MinY {
				spo2MinY = box.Min.Y
			}
			if box.Max.Y > spo2MaxY {
				spo2MaxY = box.Max.Y
			}
		} else {
			// RIGHT HALF - HR
			rightCount++
			if box.Min.X < hrMinX {
				hrMinX = box.Min.X
			}
			if box.Max.X > hrMaxX {
				hrMaxX = box.Max.X
			}
			if box.Min.Y < hrMinY {
				hrMinY = box.Min.Y
			}
			if box.Max.Y > hrMaxY {
				hrMaxY = box.Max.Y
			}
		}
	}

	if DEBUG {
		fmt.Printf("DEBUG: Split at center X=%d: %d boxes left (SpO2), %d boxes right (HR)\n",
			centerX, leftCount, rightCount)
		fmt.Printf("DEBUG: SpO2 merged area: X[%d-%d] Y[%d-%d], Size: %dx%d\n",
			spo2MinX, spo2MaxX, spo2MinY, spo2MaxY,
			spo2MaxX-spo2MinX, spo2MaxY-spo2MinY)
		fmt.Printf("DEBUG: HR merged area:   X[%d-%d] Y[%d-%d], Size: %dx%d\n",
			hrMinX, hrMaxX, hrMinY, hrMaxY,
			hrMaxX-hrMinX, hrMaxY-hrMinY)
	}

	return DisplayAreas{
		SpO2: image.Rect(spo2MinX, spo2MinY, spo2MaxX, spo2MaxY),
		HR:   image.Rect(hrMinX, hrMinY, hrMaxX, hrMaxY),
	}
}