clark-stevenson · October 2, 2018 15:00 · Oct 2, 2018
diff --git a/fit.ts b/fit.ts
@@ -0,0 +1,65 @@
+/**
+ * Copyright (C) 2014 Justin Windle, http://soulwire.co.uk
+ *
+ * Modified version of https://github.com/soulwire/fit.js/
+ *
+ * Fits a Rectangle into a Rectangle returning the transform
+ */
+
+interface FitSettings {
+  xAlign: 'center' | 'bottom' | 'right' | 'left' | 'top';
+  yAlign: 'center' | 'bottom' | 'right' | 'left' | 'top';
+  cover: boolean;
+}
+
+interface FitRectangle {
+  x: number;
+  y: number;
+  width: number;
+  height: number;
+}
+
+interface FitTransform extends FitRectangle {
+  tx: number;
+  ty: number;
+  scale: number;
+}
+
+const defaultSettings: FitSettings = {
+  xAlign: 'left',
+  yAlign: 'top',
+  cover: false
+};
+
+/**
+ * Fit a rect into a area returning a transform
+ * @param rect - the source rectangle is what we want to fit
+ * @param area - the area rectangle is what the rect fits into
+ * @param settings - any optional settings
+ */
+export function fit(rect: FitRectangle, area: FitRectangle, settings = defaultSettings) {
+  const sx = area.width / rect.width;
+  const sy = area.height / rect.height;
+  const ra = rect.width / rect.height;
+  const rb = area.width / area.height;
+  const sH = settings.cover ? sy : sx;
+  const sV = settings.cover ? sx : sy;
+  const scale = ra >= rb ? sH : sV;
+  const w = rect.width * scale;
+  const h = rect.height * scale;
+  const tx = settings.xAlign === 'center' ? 0.5 * (w - area.width) : settings.xAlign === 'right' ? w - area.width : 0.0;
+  const ty = settings.yAlign === 'center' ? 0.5 * (h - area.height) : settings.yAlign === 'bottom' ? h - area.height : 0.0;
+
+  const transform: FitTransform = {
+    tx: area.x - tx - rect.x,
+    ty: area.y - ty - rect.y,
+    x: area.x - tx - rect.x * scale,
+    y: area.y - ty - rect.y * scale,
+    height: rect.height * scale,
+    width: rect.width * scale,
+
+    scale: scale
+  };
+
+  return transform;
+}