place/storage/tile.go

package storage

import (
	"bytes"
	"image"
	"image/draw"
	"image/png"
	"os"
)

type tile struct {
	dirty bool
	path  string
	image *image.RGBA
}

func (t *tile) load(path string, tileSize int) error {
	t.image = image.NewRGBA(image.Rect(0, 0, tileSize, tileSize))
	t.path = path
	file, err := os.Open(path)
	if err != nil {
		t.fill()
		return t.save()
	}
	defer file.Close()

	img, _, err := image.Decode(file)
	if err != nil {
		t.fill()
		return t.save()
	}

	draw.Draw(t.image, img.Bounds(), img, img.Bounds().Min, draw.Src)
	t.dirty = false

	return nil
}

func (t *tile) save() error {
	file, err := os.OpenFile(t.path, os.O_WRONLY|os.O_CREATE, 0644)
	if err != nil {
		return err
	}
	defer file.Close()

	err = png.Encode(file, t.image)
	t.dirty = false
	return err
}

func (t *tile) fill() {
	draw.Draw(t.image, t.image.Bounds(), &image.Uniform{C: image.White}, image.Point{}, draw.Src)
}

func (t *tile) toBytesPNG() (*bytes.Buffer, error) {
	buffer := &bytes.Buffer{}
	err := png.Encode(buffer, t.image)
	return buffer, err
}

func (t *tile) size() image.Point {
	return t.image.Bounds().Size()
}