diff --git a/src/core/colorspace.js b/src/core/colorspace.js
index fc0bad183..e6fce2d13 100644
--- a/src/core/colorspace.js
+++ b/src/core/colorspace.js
@@ -886,16 +886,56 @@ class DeviceCmykCS extends ColorSpace {
  *
  * The default color is `new Float32Array([0])`.
  */
-const CalGrayCS = (function CalGrayCSClosure() {
-  function convertToRgb(cs, src, srcOffset, dest, destOffset, scale) {
+class CalGrayCS extends ColorSpace {
+  constructor(whitePoint, blackPoint, gamma) {
+    super("CalGray", 1);
+
+    if (!whitePoint) {
+      throw new FormatError(
+        "WhitePoint missing - required for color space CalGray"
+      );
+    }
+    // Translate arguments to spec variables.
+    [this.XW, this.YW, this.ZW] = whitePoint;
+    [this.XB, this.YB, this.ZB] = blackPoint || [0, 0, 0];
+    this.G = gamma || 1;
+
+    // Validate variables as per spec.
+    if (this.XW < 0 || this.ZW < 0 || this.YW !== 1) {
+      throw new FormatError(
+        `Invalid WhitePoint components for ${this.name}, no fallback available`
+      );
+    }
+
+    if (this.XB < 0 || this.YB < 0 || this.ZB < 0) {
+      info(`Invalid BlackPoint for ${this.name}, falling back to default.`);
+      this.XB = this.YB = this.ZB = 0;
+    }
+
+    if (this.XB !== 0 || this.YB !== 0 || this.ZB !== 0) {
+      warn(
+        `${this.name}, BlackPoint: XB: ${this.XB}, YB: ${this.YB}, ` +
+          `ZB: ${this.ZB}, only default values are supported.`
+      );
+    }
+
+    if (this.G < 1) {
+      info(
+        `Invalid Gamma: ${this.G} for ${this.name}, falling back to default.`
+      );
+      this.G = 1;
+    }
+  }
+
+  #toRgb(src, srcOffset, dest, destOffset, scale) {
     // A represents a gray component of a calibrated gray space.
     // A <---> AG in the spec
     const A = src[srcOffset] * scale;
-    const AG = A ** cs.G;
+    const AG = A ** this.G;
 
-    // Computes L as per spec. ( = cs.YW * AG )
+    // Computes L as per spec. ( = this.YW * AG )
     // Except if other than default BlackPoint values are used.
-    const L = cs.YW * AG;
+    const L = this.YW * AG;
     // http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html, Ch 4.
     // Convert values to rgb range [0, 255].
     const val = Math.max(295.8 * L ** 0.3333333333333333 - 40.8, 0);
@@ -904,91 +944,36 @@ const CalGrayCS = (function CalGrayCSClosure() {
     dest[destOffset + 2] = val;
   }
 
-  // eslint-disable-next-line no-shadow
-  class CalGrayCS extends ColorSpace {
-    constructor(whitePoint, blackPoint, gamma) {
-      super("CalGray", 1);
-
-      if (!whitePoint) {
-        throw new FormatError(
-          "WhitePoint missing - required for color space CalGray"
-        );
-      }
-      blackPoint ||= [0, 0, 0];
-      gamma ||= 1;
-
-      // Translate arguments to spec variables.
-      this.XW = whitePoint[0];
-      this.YW = whitePoint[1];
-      this.ZW = whitePoint[2];
-
-      this.XB = blackPoint[0];
-      this.YB = blackPoint[1];
-      this.ZB = blackPoint[2];
-
-      this.G = gamma;
-
-      // Validate variables as per spec.
-      if (this.XW < 0 || this.ZW < 0 || this.YW !== 1) {
-        throw new FormatError(
-          `Invalid WhitePoint components for ${this.name}` +
-            ", no fallback available"
-        );
-      }
-
-      if (this.XB < 0 || this.YB < 0 || this.ZB < 0) {
-        info(`Invalid BlackPoint for ${this.name}, falling back to default.`);
-        this.XB = this.YB = this.ZB = 0;
-      }
-
-      if (this.XB !== 0 || this.YB !== 0 || this.ZB !== 0) {
-        warn(
-          `${this.name}, BlackPoint: XB: ${this.XB}, YB: ${this.YB}, ` +
-            `ZB: ${this.ZB}, only default values are supported.`
-        );
-      }
-
-      if (this.G < 1) {
-        info(
-          `Invalid Gamma: ${this.G} for ${this.name}, ` +
-            "falling back to default."
-        );
-        this.G = 1;
-      }
+  getRgbItem(src, srcOffset, dest, destOffset) {
+    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
+      assert(
+        dest instanceof Uint8ClampedArray,
+        'CalGrayCS.getRgbItem: Unsupported "dest" type.'
+      );
     }
+    this.#toRgb(src, srcOffset, dest, destOffset, 1);
+  }
 
-    getRgbItem(src, srcOffset, dest, destOffset) {
-      if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
-        assert(
-          dest instanceof Uint8ClampedArray,
-          'CalGrayCS.getRgbItem: Unsupported "dest" type.'
-        );
-      }
-      convertToRgb(this, src, srcOffset, dest, destOffset, 1);
+  getRgbBuffer(src, srcOffset, count, dest, destOffset, bits, alpha01) {
+    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
+      assert(
+        dest instanceof Uint8ClampedArray,
+        'CalGrayCS.getRgbBuffer: Unsupported "dest" type.'
+      );
     }
+    const scale = 1 / ((1 << bits) - 1);
 
-    getRgbBuffer(src, srcOffset, count, dest, destOffset, bits, alpha01) {
-      if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
-        assert(
-          dest instanceof Uint8ClampedArray,
-          'CalGrayCS.getRgbBuffer: Unsupported "dest" type.'
-        );
-      }
-      const scale = 1 / ((1 << bits) - 1);
-
-      for (let i = 0; i < count; ++i) {
-        convertToRgb(this, src, srcOffset, dest, destOffset, scale);
-        srcOffset += 1;
-        destOffset += 3 + alpha01;
-      }
-    }
-
-    getOutputLength(inputLength, alpha01) {
-      return inputLength * (3 + alpha01);
+    for (let i = 0; i < count; ++i) {
+      this.#toRgb(src, srcOffset, dest, destOffset, scale);
+      srcOffset += 1;
+      destOffset += 3 + alpha01;
     }
   }
-  return CalGrayCS;
-})();
+
+  getOutputLength(inputLength, alpha01) {
+    return inputLength * (3 + alpha01);
+  }
+}
 
 /**
  * CalRGBCS: Based on "PDF Reference, Sixth Ed", p.247