identicon-algorithms/xBitPolygons.go

package main

import (
	"slices"
	"strconv"

	"github.com/fogleman/gg"
)

func XBitPolygons(dc *gg.Context, username string, columns int, rows int) {
	hash := hash(username)

	dc.SetRGB255(255, 255, 255)
	dc.DrawRectangle(0, 0, 800, 800)
	dc.Fill()

	colorString := hash[0:6]
	r, g, b := rgbFromHex(colorString)
	dc.SetRGB255(r, g, b)

	enabledVertices := [][]bool{}
	for _, character := range hash[6:6+rows+1] {
		integer, _ := strconv.ParseUint(string(character), 16, columns/2+1)
		row := []bool{}
		for j := range columns/2+1 {
			on := hasBit(integer, j)
			row = append(row, on)
		}
		enabledVertices = append(enabledVertices, row)
	}

	w := 800 / columns
	h := 800 / rows

	for i := range rows {
		for j := range columns/2 {
			topLeft, tlx, tly := enabledVertices[i][j], float64(j*w), float64(i*h)
			topRight, trx, try := enabledVertices[i][j+1], float64(j*w+w), float64(i*h)
			bottomRight, brx, bry := enabledVertices[i+1][j+1], float64(j*w+w), float64(i*h+h)
			bottomLeft, blx, bly := enabledVertices[i+1][j], float64(j*w), float64(i*h+h)
			mx, my := tlx + float64(w/2), tly + float64(h/2)

			count := 0
			if topLeft {count++}
			if topRight {count++}
			if bottomRight {count++}
			if bottomLeft {count++}

			if topLeft && topRight {
				dc.NewSubPath()
				dc.MoveTo(mx, my)
				dc.LineTo(tlx, tly)
				dc.LineTo(trx, try)
				dc.ClosePath()
			}

			if topRight && bottomRight {
				dc.NewSubPath()
				dc.MoveTo(mx, my)
				dc.LineTo(trx, try)
				dc.LineTo(brx, bry)
				dc.ClosePath()
			}

			if bottomRight && bottomLeft {
				dc.NewSubPath()
				dc.MoveTo(mx, my)
				dc.LineTo(brx, bry)
				dc.LineTo(blx, bly)
				dc.ClosePath()
			}

			if bottomLeft && topLeft {
				dc.NewSubPath()
				dc.MoveTo(mx, my)
				dc.LineTo(blx, bly)
				dc.LineTo(tlx, tly)
				dc.ClosePath()
			}
			dc.Fill()
		}
	}

	// Reverse
	for i := range len(enabledVertices) {
		slices.Reverse(enabledVertices[i])
	}

	// Mirror left side
	for i := range rows {
		for j := range columns/2 {
			topLeft, tlx, tly := enabledVertices[i][j], float64(w*(columns/2)+j*w), float64(i*h)
			topRight, trx, try := enabledVertices[i][j+1], float64(w*(columns/2)+j*w+w), float64(i*h)
			bottomRight, brx, bry := enabledVertices[i+1][j+1], float64(w*(columns/2)+j*w+w), float64(i*h+h)
			bottomLeft, blx, bly := enabledVertices[i+1][j], float64(w*(columns/2)+j*w), float64(i*h+h)
			mx, my := tlx+float64(w/2), tly+float64(h/2)

			count := 0
			if topLeft {count++}
			if topRight {count++}
			if bottomRight {count++}
			if bottomLeft {count++}

			if topLeft && topRight {
				dc.NewSubPath()
				dc.MoveTo(mx, my)
				dc.LineTo(tlx, tly)
				dc.LineTo(trx, try)
				dc.ClosePath()
			}

			if topRight && bottomRight {
				dc.NewSubPath()
				dc.MoveTo(mx, my)
				dc.LineTo(trx, try)
				dc.LineTo(brx, bry)
				dc.ClosePath()
			}

			if bottomRight && bottomLeft {
				dc.NewSubPath()
				dc.MoveTo(mx, my)
				dc.LineTo(brx, bry)
				dc.LineTo(blx, bly)
				dc.ClosePath()
			}

			if bottomLeft && topLeft {
				dc.NewSubPath()
				dc.MoveTo(mx, my)
				dc.LineTo(blx, bly)
				dc.LineTo(tlx, tly)
				dc.ClosePath()
			}
			dc.Fill()
		}
	}
}