map-dots/imaging/circles.go

package imaging

import (
	"image"

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

	circleRadius := 10 // Replace with your desired fixed radius

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

	var minLat, maxLat, minLon, maxLon float64
	for _, circle := range circles {
		if circle.Latitude < minLat {
			minLat = circle.Latitude
		}
		if circle.Latitude > maxLat {
			maxLat = circle.Latitude
		}
		if circle.Longitude < minLon {
			minLon = circle.Longitude
		}
		if circle.Longitude > maxLon {
			maxLon = circle.Longitude
		}
	}

	for _, circle := range circles {
		// Convert latitude and longitude to pixel position on the canvas
		pixelX, pixelY := convertCoordinatesToPixels(circle.Latitude, circle.Longitude, minLat, maxLat, minLon, maxLon, canvasWidth, canvasHeight)

		// Draw the circle on the canvas using gg
		dc.DrawCircle(float64(pixelX), float64(pixelY), float64(circleRadius))
		dc.SetRGBA(1, 1, 1, 0.5) // Circle fill color (white with 50% opacity)
		dc.Fill()
	}

	dc.Clip() // Apply clipping

	// Optional: Save the canvas as an image file
	err := dc.SavePNG("output.png")
	if err != nil {
		// Handle error
	}
}

func convertCoordinatesToPixels(latitude, longitude float64, minLat, maxLat, minLon, maxLon float64, canvasWidth, canvasHeight int) (int, int) {
	// Calculate margins as a percentage of canvas dimensions
	marginPercentage := 0.1 // 10% margin
	marginWidth := int(float64(canvasWidth) * marginPercentage)
	marginHeight := int(float64(canvasHeight) * marginPercentage)

	// Adjust the bounding box with margins
	minLat -= (maxLat - minLat) * marginPercentage
	maxLat += (maxLat - minLat) * marginPercentage
	minLon -= (maxLon - minLon) * marginPercentage
	maxLon += (maxLon - minLon) * marginPercentage

	// Calculate the position within the adjusted bounding box
	latPercentage := (latitude - minLat) / (maxLat - minLat)
	lonPercentage := (longitude - minLon) / (maxLon - minLon)

	// Calculate the pixel positions on the canvas
	pixelX := int(lonPercentage*float64(canvasWidth-marginWidth*2)) + marginWidth
	pixelY := canvasHeight - (int(latPercentage*float64(canvasHeight-marginHeight*2)) + marginHeight)

	return pixelX, pixelY
}