map-dots/imaging/circles.go

package imaging

import (
	"image"
	"math"

	"git.fjla.uk/fred.boniface/map-dots/data"
	"git.fjla.uk/fred.boniface/map-dots/log"
	"github.com/fogleman/gg"
)

func mapCirclesToCanvas(img *image.RGBA, locations []data.LocationData) image.Image {
	log.Msg.Debug("Mapping locations to canvas")
	dc := gg.NewContextForRGBA(img)
	dc.SetRGB(1, 1, 1) // Set canvas background color (white in this case)

	//circleRadius := 4 // Replace with your desired fixed radius

	bounds := img.Bounds()
	canvasWidth := bounds.Max.X - bounds.Min.X
	canvasHeight := bounds.Max.Y - bounds.Min.Y
	margin := 0.1

	var minLat, maxLat, minLon, maxLon = math.MaxFloat64, -math.MaxFloat64, math.MaxFloat64, -math.MaxFloat64
	for _, loc := range locations {
		if loc.Latitude < minLat {
			minLat = loc.Latitude
		}
		if loc.Latitude > maxLat {
			maxLat = loc.Latitude
		}
		if loc.Longitude < minLon {
			minLon = loc.Longitude
		}
		if loc.Longitude > maxLon {
			maxLon = loc.Longitude
		}
	}

	latRange := maxLat - minLat
	lonRange := maxLon - minLon
	minLat -= latRange * margin
	maxLat += latRange * margin
	minLon -= lonRange * margin
	maxLon += lonRange * margin

	minLatEqui := equirectangularProjection(minLat)
	maxLatEqui := equirectangularProjection(maxLat)

	latScale := float64(canvasHeight) / (maxLatEqui - minLatEqui)
	longScale := float64(canvasWidth) / (maxLon - minLon)

	for _, loc := range locations {
		x := int((loc.Longitude - minLon) * longScale)
		// Invert the Y-axis calculation
		y := canvasHeight - int((equirectangularProjection(loc.Latitude)-minLatEqui)*latScale)
		// Draw a dot (circle) at (x, y)
		dc.DrawCircle(float64(x), float64(y), 2)
		dc.SetRGBA(1, 1, 1, 0.3333333333) // Set dot color (black)
		dc.Fill()
	}

	return img
}

/*
func convertCoordinatesToPixels(latitude, longitude float64, centerLat, centerLon, latRange, lonRange float64, canvasWidth, canvasHeight int) (int, int) {
	// Calculate normalized latitude and longitude distances from the center
	latDist := (latitude - centerLat) / (latRange * 0.5)
	lonDist := (longitude - centerLon) / (lonRange * 0.5)

	// Calculate the maximum distance from the center as a proportion of canvas size
	maxDistance := math.Max(math.Abs(latDist), math.Abs(lonDist))

	// Adjust the normalized distances to match the canvas size with margins
	adjustedLatDist := latDist / maxDistance * 0.45
	adjustedLonDist := lonDist / maxDistance * 0.45

	// Calculate pixel positions
	pixelX := int((adjustedLonDist + 0.5) * float64(canvasWidth))
	pixelY := int((0.5 - adjustedLatDist) * float64(canvasHeight))

	return pixelX, pixelY
}*/

func equirectangularProjection(lat float64) float64 {
	return lat * (math.Pi / 180) // Convert degrees to radians
}