Make image paths relative to the .deck file they're referenced from

deck.go

@@ -44,7 +44,8 @@ func LoadDeck(dev *streamdeck.Device, base string, deck string) (*Deck, error) {
 		File: abs,
 	}
 	if dc.Background != "" {
-		if err := d.loadBackground(dc.Background); err != nil {
+		bgpath := findImage(filepath.Dir(abs), dc.Background)
+		if err := d.loadBackground(bgpath); err != nil {
 			return nil, err
 		}
 	}

images.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	"path/filepath"
+)
+
+func findImage(base, icon string) string {
+	if !filepath.IsAbs(icon) {
+		icon = filepath.Join(base, icon)
+	}
+	abs, err := filepath.Abs(icon)
+	if err != nil {
+		return icon
+	}
+
+	return abs
+}

widget_button.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"image"
+	"path/filepath"
 	"sync"
 
 	"github.com/muesli/streamdeck"
@@ -31,7 +32,10 @@ func (w *ButtonWidget) Update(dev *streamdeck.Device) error {
 			bounds := img.Bounds()
 
 			if w.icon != "" {
-				err = drawImage(img, w.icon, iconsize, image.Pt(-1, margin))
+				err = drawImage(img,
+					findImage(filepath.Dir(deck.File), w.icon),
+					iconsize,
+					image.Pt(-1, margin))
 
 				bounds.Min.Y += iconsize + margin
 				bounds.Max.Y -= margin
@@ -44,7 +48,10 @@ func (w *ButtonWidget) Update(dev *streamdeck.Device) error {
 				w.fontsize,
 				image.Pt(-1, -1))
 		} else if w.icon != "" {
-			err = drawImage(img, w.icon, height, image.Pt(-1, -1))
+			err = drawImage(img,
+				findImage(filepath.Dir(deck.File), w.icon),
+				height,
+				image.Pt(-1, -1))
 		}
 
 		if err != nil {