Add m-esr52 at 52.6.0

1 files changed, 85 insertions, 0 deletions

diff --git a/toolkit/modules/Color.jsm b/toolkit/modules/Color.jsm
new file mode 100644
index 000000000..00a9bd953
--- /dev/null
+++ b/toolkit/modules/Color.jsm
@@ -0,0 +1,85 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = ["Color"];
+
+/**
+ * Color class, which describes a color.
+ * In the future, this object may be extended to allow for conversions between
+ * different color formats and notations, support transparency.
+ *
+ * @param {Number} r Red color component
+ * @param {Number} g Green color component
+ * @param {Number} b Blue color component
+ */
+function Color(r, g, b) {
+  this.r = r;
+  this.g = g;
+  this.b = b;
+}
+
+Color.prototype = {
+  /**
+   * Formula from W3C's WCAG 2.0 spec's relative luminance, section 1.4.1,
+   * http://www.w3.org/TR/WCAG20/.
+   *
+   * @return {Number} Relative luminance, represented as number between 0 and 1.
+   */
+  get relativeLuminance() {
+    let colorArr = [this.r, this.b, this.g].map(color => {
+      color = parseInt(color, 10);
+      if (color <= 10)
+        return color / 255 / 12.92;
+      return Math.pow(((color / 255) + 0.055) / 1.055, 2.4);
+    });
+    return colorArr[0] * 0.2126 +
+           colorArr[1] * 0.7152 +
+           colorArr[2] * 0.0722;
+  },
+
+  /**
+   * @return {Boolean} TRUE if the color value can be considered bright.
+   */
+  get isBright() {
+    // Note: this is a high enough value to be considered as 'bright', but was
+    //       decided upon empirically.
+    return this.relativeLuminance > 0.7;
+  },
+
+  /**
+   * Get the contrast ratio between the current color and a second other color.
+   * A common use case is to express the difference between a foreground and a
+   * background color in numbers.
+   * Formula from W3C's WCAG 2.0 spec's contrast ratio, section 1.4.1,
+   * http://www.w3.org/TR/WCAG20/.
+   *
+   * @param  {Color}  otherColor Color instance to calculate the contrast with
+   * @return {Number} Contrast ratios can range from 1 to 21, commonly written
+   *                  as 1:1 to 21:1.
+   */
+  contrastRatio(otherColor) {
+    if (!(otherColor instanceof Color))
+      throw new TypeError("The first argument should be an instance of Color");
+
+    let luminance = this.relativeLuminance;
+    let otherLuminance = otherColor.relativeLuminance;
+    return (Math.max(luminance, otherLuminance) + 0.05) /
+      (Math.min(luminance, otherLuminance) + 0.05);
+  },
+
+  /**
+   * Biased method to check if the contrast ratio between two colors is high
+   * enough to be discernable.
+   *
+   * @param  {Color} otherColor Color instance to calculate the contrast with
+   * @return {Boolean}
+   */
+  isContrastRatioAcceptable(otherColor) {
+    // Note: this is a high enough value to be considered as 'high contrast',
+    //       but was decided upon empirically.
+    return this.contrastRatio(otherColor) > 3;
+  }
+};