Verify background colour values are numbers (#4556)

Author: metsw24-max

lib/colour.mjs

@@ -146,12 +146,16 @@ function _getBackgroundColourOption (value) {
     (is.string(value) && value.length >= 3 && value.length <= 200)
   ) {
     const colour = color(value);
-    return [
-      colour.red(),
-      colour.green(),
-      colour.blue(),
-      Math.round(colour.alpha() * 255)
-    ];
+    const red = colour.red();
+    const green = colour.green();
+    const blue = colour.blue();
+    const alpha = Math.round(colour.alpha() * 255);
+    for (const [channel, component] of [['red', red], ['green', green], ['blue', blue], ['alpha', alpha]]) {
+      if (!is.number(component)) {
+        throw is.invalidParameterError(`background.${channel}`, 'number', component);
+      }
+    }
+    return [red, green, blue, alpha];
   } else {
     throw is.invalidParameterError('background', 'object or string', value);
   }

test/unit/tint.js

@@ -105,4 +105,20 @@ suite('Tint', () => {
       () => fixtures.assertMaxColourDistance(output, fixtures.expected('tint-cmyk.jpg'), maxDistance)
     );
   });
+
+  test('non-numeric colour component fails, identifying the channel', (t) => {
+    t.plan(3);
+    t.assert.throws(
+      () => sharp().tint({ r: 'fail', g: 0, b: 0 }),
+      /Expected number for background\.red but received NaN of type number/
+    );
+    t.assert.throws(
+      () => sharp().tint({ r: NaN, g: 0, b: 0 }),
+      /Expected number for background\.red but received NaN of type number/
+    );
+    t.assert.throws(
+      () => sharp().tint({ r: 0, g: 0, b: 'fail' }),
+      /Expected number for background\.blue but received NaN of type number/
+    );
+  });
 });