Internalise the map rect

internal/maps/maps.go

@@ -5,6 +5,7 @@ import (
 	"compress/gzip"
 	"encoding/binary"
 	"fmt"
+	"image"
 	"io"
 	"io/ioutil"
 	"log"
@@ -173,6 +174,15 @@ type GameMap struct {
 	Text string
 }
 
+func (m *GameMap) Rect() image.Rectangle {
+	return image.Rect(
+		int(m.Header.MinWidth),
+		int(m.Header.MinLength),
+		int(m.Header.MaxWidth),
+		int(m.Header.MaxLength),
+	)
+}
+
 // A game map contains a .txt and a .map. If they're in the same directory,
 // just pass the directory + basename to load both
 func LoadGameMap(prefix string) (*GameMap, error) {