Draw initial board

chess/board.go

@@ -0,0 +1,153 @@
+package chess
+
+import (
+	"fmt"
+	"image"
+	"image/draw"
+	"image/png"
+	"log"
+	"os"
+)
+
+type Board struct {
+	tiles [8][8]*Piece
+}
+
+func NewBoard() *Board {
+	board := &Board{}
+
+	board.mustSetPiece(Rook, Light, "a1")
+	board.mustSetPiece(Knight, Light, "b1")
+	board.mustSetPiece(Bishop, Light, "c1")
+	board.mustSetPiece(Queen, Light, "d1")
+	board.mustSetPiece(King, Light, "e1")
+	board.mustSetPiece(Bishop, Light, "f1")
+	board.mustSetPiece(Knight, Light, "g1")
+	board.mustSetPiece(Rook, Light, "h1")
+	board.mustSetPiece(Pawn, Light, "a2")
+	board.mustSetPiece(Pawn, Light, "b2")
+	board.mustSetPiece(Pawn, Light, "c2")
+	board.mustSetPiece(Pawn, Light, "d2")
+	board.mustSetPiece(Pawn, Light, "e2")
+	board.mustSetPiece(Pawn, Light, "f2")
+	board.mustSetPiece(Pawn, Light, "g2")
+	board.mustSetPiece(Pawn, Light, "h2")
+
+	board.mustSetPiece(Rook, Dark, "a8")
+	board.mustSetPiece(Knight, Dark, "b8")
+	board.mustSetPiece(Bishop, Dark, "c8")
+	board.mustSetPiece(Queen, Dark, "d8")
+	board.mustSetPiece(King, Dark, "e8")
+	board.mustSetPiece(Bishop, Dark, "f8")
+	board.mustSetPiece(Knight, Dark, "g8")
+	board.mustSetPiece(Rook, Dark, "h8")
+	board.mustSetPiece(Pawn, Dark, "a7")
+	board.mustSetPiece(Pawn, Dark, "b7")
+	board.mustSetPiece(Pawn, Dark, "c7")
+	board.mustSetPiece(Pawn, Dark, "d7")
+	board.mustSetPiece(Pawn, Dark, "e7")
+	board.mustSetPiece(Pawn, Dark, "f7")
+	board.mustSetPiece(Pawn, Dark, "g7")
+	board.mustSetPiece(Pawn, Dark, "h7")
+
+	return board
+}
+
+func (b *Board) Save(filename string) error {
+	var (
+		file  *os.File
+		img   *image.RGBA
+		piece *Piece
+		bg    *image.Uniform
+		rect  image.Rectangle
+		p     = image.Point{0, 0}
+		err   error
+	)
+
+	if file, err = os.Create(filename); err != nil {
+		return err
+	}
+	defer file.Close()
+
+	img = image.NewRGBA(image.Rect(0, 0, 1024, 1024))
+
+	for yi := 0; yi < 8; yi++ {
+		for xi := 0; xi < 8; xi++ {
+			rect = image.Rect(xi*128, yi*128, (xi*128)+128, (yi*128)+128)
+			bg = image.NewUniform(getTileColor(xi, yi))
+			draw.Draw(img, rect, bg, p, draw.Src)
+
+			piece = b.tiles[xi][yi]
+			if piece != nil {
+				draw.Draw(img, rect, piece.Image, p, draw.Over)
+			}
+		}
+	}
+
+	return png.Encode(file, img)
+}
+
+func (b *Board) SetPiece(name PieceName, color Color, position string) error {
+	var (
+		piece *Piece
+		x     int
+		y     int
+		err   error
+	)
+
+	if len(position) != 2 {
+		return fmt.Errorf("invalid position: %s", position)
+	}
+
+	if piece, err = NewPiece(name, color); err != nil {
+		return err
+	}
+
+	if x, y, err = getXY(position); err != nil {
+		return err
+	}
+
+	b.tiles[x][y] = piece
+
+	return nil
+}
+
+func (b *Board) mustSetPiece(name PieceName, color Color, position string) {
+	if err := b.SetPiece(name, color, position); err != nil {
+		log.Fatalf("cannot set piece %s: %v", name, err)
+	}
+}
+
+func getXY(position string) (int, int, error) {
+	var (
+		posX rune
+		posY rune
+		x    int
+		y    int
+	)
+	runes := []rune(position)
+	posX = runes[0]
+	posY = runes[1]
+
+	if posX < 'a' && posX > 'h' {
+		return -1, -1, fmt.Errorf("invalid posX: %s", position)
+	}
+
+	if posY < '1' && posY > '8' {
+		return -1, -1, fmt.Errorf("invalid posY: %s", position)
+	}
+
+	// image origin (0,0) is at top-left corner (a8)
+	x = int(posX - 'a')
+	y = int('8' - posY)
+
+	return x, y, nil
+}
+
+func getTileColor(x, y int) Color {
+	if x%2 == y%2 {
+		return Light
+	} else {
+		return Dark
+	}
+}

chess/piece.go

@@ -0,0 +1,73 @@
+package chess
+
+import (
+	"fmt"
+	"image"
+	"image/color"
+	"image/png"
+	"os"
+
+	"golang.org/x/image/draw"
+)
+
+type Piece struct {
+	Name  PieceName
+	Color color.Color
+	Image image.Image
+}
+
+type PieceName string
+
+const (
+	Pawn   PieceName = "p"
+	Knight PieceName = "n"
+	Bishop PieceName = "b"
+	Rook   PieceName = "r"
+	Queen  PieceName = "q"
+	King   PieceName = "k"
+)
+
+type Color color.Color
+
+var (
+	Light Color = color.RGBA{240, 217, 181, 255}
+	Dark  Color = color.RGBA{181, 136, 99, 255}
+)
+
+func NewPiece(name PieceName, color Color) (*Piece, error) {
+	var (
+		colorSuffix string
+		path        string
+		file        *os.File
+		img         image.Image
+		dst         *image.RGBA
+		err         error
+	)
+
+	colorSuffix = "l"
+	if color == Light {
+		colorSuffix = "l"
+	} else if color == Dark {
+		colorSuffix = "d"
+	} else {
+		return nil, fmt.Errorf("invalid color: %v", color)
+	}
+
+	path = fmt.Sprintf("assets/1024px-Chess_%s%st45.svg.png", name, colorSuffix)
+
+	if file, err = os.Open(path); err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	if img, err = png.Decode(file); err != nil {
+		return nil, err
+	}
+
+	// source image for each piece is 1024x1024 and board is 8x8
+	// so we need to scale each piece down to 128x128 (1024/8)
+	dst = image.NewRGBA(image.Rect(0, 0, 128, 128))
+	draw.CatmullRom.Scale(dst, dst.Rect, img, img.Bounds(), draw.Over, nil)
+
+	return &Piece{Name: name, Color: color, Image: dst}, nil
+}

go.mod

@@ -0,0 +1,5 @@
+module github.com/ekzyis/sn-chess
+
+go 1.23.0
+
+require golang.org/x/image v0.20.0

go.sum

@@ -0,0 +1,2 @@
+golang.org/x/image v0.20.0 h1:7cVCUjQwfL18gyBJOmYvptfSHS8Fb3YUDtfLIZ7Nbpw=
+golang.org/x/image v0.20.0/go.mod h1:0a88To4CYVBAHp5FXJm8o7QbUl37Vd85ply1vyD8auM=

main.go

@@ -0,0 +1,13 @@
+package main
+
+import (
+	"github.com/ekzyis/sn-chess/chess"
+)
+
+func main() {
+	var (
+		b = chess.NewBoard()
+	)
+
+	b.Save("board.png")
+}