diff --git a/src/core/evaluator.js b/src/core/evaluator.js
index 2f76c26c7..8a8543381 100644
--- a/src/core/evaluator.js
+++ b/src/core/evaluator.js
@@ -16,7 +16,7 @@
  */
 /* globals assert, assertWellFormed, ColorSpace, Dict, Encodings, error,
            ErrorFont, Font, FONT_IDENTITY_MATRIX, fontCharsToUnicode, FontFlags,
-           info, isArray, isCmd, isDict, isEOF, isName, isNum,
+           ImageKind, info, isArray, isCmd, isDict, isEOF, isName, isNum,
            isStream, isString, JpegStream, Lexer, Metrics, Name, Parser,
            Pattern, PDFImage, PDFJS, serifFonts, stdFontMap, symbolsFonts,
            getTilingPatternIR, warn, Util, Promise, LegacyPromise,
@@ -166,8 +166,8 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
           (w + h) < SMALL_IMAGE_DIMENSIONS) {
         var imageObj = new PDFImage(this.xref, resources, image,
                                     inline, null, null);
-        // We force the use of 'rgba_32bpp' images here, because we can't
-        // handle any other kind.
+        // We force the use of RGBA_32BPP images here, because we can't handle
+        // any other kind.
         var imgData = imageObj.createImageData(/* forceRGBA = */ true);
         operatorList.addOp(OPS.paintInlineImageXObject, [imgData]);
         return;
@@ -1321,7 +1321,7 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
         // replacing queue items
         squash(fnArray, j, count * 4, OPS.paintInlineImageXObjectGroup);
         argsArray.splice(j, count * 4,
-          [{width: imgWidth, height: imgHeight, kind: 'rgba_32bpp',
+          [{width: imgWidth, height: imgHeight, kind: ImageKind.RGBA_32BPP,
             data: imgData}, map]);
         i = j;
         ii = argsArray.length;
diff --git a/src/core/image.js b/src/core/image.js
index ef4c319d4..084e6e339 100644
--- a/src/core/image.js
+++ b/src/core/image.js
@@ -14,8 +14,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* globals ColorSpace, error, isArray, isStream, JpegStream, Name, Promise,
-           Stream, warn, LegacyPromise */
+/* globals ColorSpace, error, isArray, ImageKind, isStream, JpegStream, Name,
+           Promise, Stream, warn, LegacyPromise */
 
 'use strict';
 
@@ -444,9 +444,9 @@ var PDFImage = (function PDFImageClosure() {
         // complications, we avoid expanding by 1.333x to RGBA form.
         var kind;
         if (this.colorSpace.name === 'DeviceGray' && bpc === 1) {
-          kind = 'grayscale_1bpp';
+          kind = ImageKind.GRAYSCALE_1BPP;
         } else if (this.colorSpace.name === 'DeviceRGB' && bpc === 8) {
-          kind = 'rgb_24bpp';
+          kind = ImageKind.RGB_24BPP;
         }
         if (kind && !this.smask && !this.mask && !this.needsDecode &&
             drawWidth === originalWidth && drawHeight === originalHeight) {
@@ -482,7 +482,7 @@ var PDFImage = (function PDFImageClosure() {
 
       this.undoPreblend(rgbaBuf, drawWidth, actualHeight);
 
-      imgData.kind = 'rgba_32bpp';
+      imgData.kind = ImageKind.RGBA_32BPP;
       imgData.data = rgbaBuf;
       return imgData;
     },
diff --git a/src/display/canvas.js b/src/display/canvas.js
index a299321e6..dbf5f7161 100644
--- a/src/display/canvas.js
+++ b/src/display/canvas.js
@@ -15,9 +15,9 @@
  * limitations under the License.
  */
 /* globals ColorSpace, DeviceCmykCS, DeviceGrayCS, DeviceRgbCS, error,
-           FONT_IDENTITY_MATRIX, IDENTITY_MATRIX, ImageData, isArray, isNum,
-           TilingPattern, OPS, Promise, Util, warn, assert, info, shadow,
-           TextRenderingMode, getShadingPatternFromIR */
+           FONT_IDENTITY_MATRIX, IDENTITY_MATRIX, ImageData, ImageKind,
+           isArray, isNum, TilingPattern, OPS, Promise, Util, warn, assert,
+           info, shadow, TextRenderingMode, getShadingPatternFromIR */
 
 'use strict';
 
@@ -457,7 +457,7 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
     // There are multiple forms in which the pixel data can be passed, and
     // imgData.kind tells us which one this is.
 
-    if (imgData.kind === 'grayscale_1bpp') {
+    if (imgData.kind === ImageKind.GRAYSCALE_1BPP) {
       // Grayscale, 1 bit per pixel (i.e. black-and-white).
       var destDataLength = dest.length;
       var srcLength = src.byteLength;
@@ -505,7 +505,7 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
         ctx.putImageData(chunkImgData, 0, i * fullChunkHeight);
       }
 
-    } else if (imgData.kind === 'rgba_32bpp') {
+    } else if (imgData.kind === ImageKind.RGBA_32BPP) {
       // RGBA, 32-bits per pixel.
       var haveSetAndSubarray = 'set' in dest && 'subarray' in src;
 
@@ -524,7 +524,7 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
         ctx.putImageData(chunkImgData, 0, i * fullChunkHeight);
       }
 
-    } else if (imgData.kind === 'rgb_24bpp') {
+    } else if (imgData.kind === ImageKind.RGB_24BPP) {
       // RGB, 24-bits per pixel.
       for (var i = 0; i < totalChunks; i++) {
         var thisChunkHeight =
diff --git a/src/shared/util.js b/src/shared/util.js
index 312445565..f3f6289ca 100644
--- a/src/shared/util.js
+++ b/src/shared/util.js
@@ -38,6 +38,12 @@ var TextRenderingMode = {
   ADD_TO_PATH_FLAG: 4
 };
 
+var ImageKind = {
+  GRAYSCALE_1BPP: 1,
+  RGB_24BPP: 2,
+  RGBA_32BPP: 3
+};
+
 // The global PDFJS object exposes the API
 // In production, it will be declared outside a global wrapper
 // In development, it will be declared here