# image

## Introduction

Image is an chess image utility that converts board positions into [SVG](https://en.wikipedia.org/wiki/Scalable_Vector_Graphics), or Scalable Vector Graphics, images.  [svgo](https://github.com/ajstarks/svgo), the only outside dependency, is used to construct the SVG document.

## Usage

### SVG 

The SVG function is the primary exported function of the package.  It writes an SVG document to the io.Writer given.  

```go
file, _ := os.Open("output.svg")
defer file.Close()
fenStr := "rnbqkbnr/pppppppp/8/8/3P4/8/PPP1PPPP/RNBQKBNR b KQkq - 0 1"
pos := &chess.Position{}
pos.UnmarshalText([]byte(fenStr))
image.SVG(file, pos.Board())
```

### Dark / Light Square Customization

The default colors, shown in the example SVG below, are (235, 209, 166) for light squares and (165, 117, 81) for dark squares.  The light and dark squares can be customized using the SquareColors() option. 

```go
white := color.RGBA{255, 255, 255, 1}
gray := color.RGBA{120, 120, 120, 1}
sqrs := image.SquareColors(white, gray)
image.SVG(file, pos.Board(), sqrs)
```

### Marked Squares

MarkSquares is designed to be used as an optional argument to the SVG function.  It marks the given squares with the color.  A possible usage includes marking squares of the previous move.

```go
yellow := color.RGBA{255, 255, 0, 1}
mark := image.MarkSquares(yellow, chess.D2, chess.D4)
image.SVG(file, pos.Board(), mark)
```

### Example Program

```go
package main

import (
	"image/color"
	"log"
	"os"

	"github.com/notnil/chess"
	"github.com/notnil/chess/image"
)

func main() {
    // create file
    f, err := os.Create("example.svg")
    if err != nil {
        log.Fatal(err)
    }
    defer f.Close()

    // create board position
    fenStr := "rnbqkbnr/pppppppp/8/8/3P4/8/PPP1PPPP/RNBQKBNR b KQkq - 0 1"
    pos := &chess.Position{}
    if err := pos.UnmarshalText([]byte(fenStr)); err != nil {
        log.Fatal(err)
    }

    // write board SVG to file
    yellow := color.RGBA{255, 255, 0, 1}
    mark := image.MarkSquares(yellow, chess.D2, chess.D4)
    if err := image.SVG(f, pos.Board(), mark); err != nil {
        log.Fatal(err)
    }
}
```

### Example Program Result

![rnbqkbnr/pppppppp/8/8/3P4/8/PPP1PPPP/RNBQKBNR b KQkq - 0 1](/example.svg)