diff --git a/gm/gmmain.cpp b/gm/gmmain.cpp
index b2cc8d8..2f18aaa 100644
--- a/gm/gmmain.cpp
+++ b/gm/gmmain.cpp
@@ -15,6 +15,7 @@
 
 #include "gm.h"
 #include "system_preferences.h"
+#include "SkBitmapChecksummer.h"
 #include "SkColorPriv.h"
 #include "SkData.h"
 #include "SkDeferredCanvas.h"
@@ -32,6 +33,8 @@
 #include "SkTileGridPicture.h"
 #include "SamplePipeControllers.h"
 
+#include "json/value.h"
+
 #if SK_SUPPORT_GPU
 #include "GrContextFactory.h"
 #include "GrRenderTarget.h"
@@ -74,6 +77,16 @@
 const static ErrorBitfield ERROR_READING_REFERENCE_IMAGE = 0x08;
 const static ErrorBitfield ERROR_WRITING_REFERENCE_IMAGE = 0x10;
 
+const static char kJsonKey_ActualResults[]   = "actual-results";
+const static char kJsonKey_ActualResults_Failed[]        = "failed";
+const static char kJsonKey_ActualResults_FailureIgnored[]= "failure-ignored";
+const static char kJsonKey_ActualResults_Succeeded[]     = "succeeded";
+const static char kJsonKey_ActualResults_AnyStatus_Checksum[]    = "checksum";
+
+const static char kJsonKey_ExpectedResults[] = "expected-results";
+const static char kJsonKey_ExpectedResults_Checksums[]     = "checksums";
+const static char kJsonKey_ExpectedResults_IgnoreFailure[] = "ignore-failure";
+
 using namespace skiagm;
 
 /*
@@ -570,24 +583,57 @@
     ErrorBitfield compare_to_reference_image_on_disk(
       const char readPath [], const SkString& name, SkBitmap &bitmap,
       const char diffPath [], const char renderModeDescriptor []) {
+        ErrorBitfield retval;
         SkString path = make_filename(readPath, "", name, "png");
         SkBitmap referenceBitmap;
-        if (SkImageDecoder::DecodeFile(path.c_str(), &referenceBitmap,
+        Json::Value expectedChecksumsArray;
+
+        bool decodedReferenceBitmap =
+            SkImageDecoder::DecodeFile(path.c_str(), &referenceBitmap,
                                        SkBitmap::kARGB_8888_Config,
                                        SkImageDecoder::kDecodePixels_Mode,
-                                       NULL)) {
-            return compare_to_reference_image_in_memory(name, bitmap,
-                                                        referenceBitmap,
-                                                        diffPath,
-                                                        renderModeDescriptor);
+                                       NULL);
+        if (decodedReferenceBitmap) {
+            expectedChecksumsArray.append(Json::UInt64(
+                SkBitmapChecksummer::Compute64(referenceBitmap)));
+            retval = compare_to_reference_image_in_memory(name, bitmap,
+                                                          referenceBitmap,
+                                                          diffPath,
+                                                          renderModeDescriptor);
         } else {
             if (fNotifyMissingReadReference) {
                 fprintf(stderr, "FAILED to read %s\n", path.c_str());
             }
             RecordError(ERROR_READING_REFERENCE_IMAGE, name,
                         renderModeDescriptor);
-            return ERROR_READING_REFERENCE_IMAGE;
+            retval = ERROR_READING_REFERENCE_IMAGE;
         }
+
+        // Add this result to the appropriate JSON collection of actual results,
+        // depending on status.
+        Json::Value actualResults;
+        actualResults[kJsonKey_ActualResults_AnyStatus_Checksum] = Json::UInt64(
+            SkBitmapChecksummer::Compute64(bitmap));
+        if (decodedReferenceBitmap) {
+            if (ERROR_NONE == retval) {
+                fJsonActualResults_Succeeded[name.c_str()] = actualResults;
+            } else {
+                fJsonActualResults_Failed[name.c_str()] = actualResults;
+            }
+        } else {
+            fJsonActualResults_FailureIgnored[name.c_str()] = actualResults;
+        }
+
+        // Add this test to the JSON collection of expected results.
+        // For now, we assume that this collection starts out empty and we
+        // just fill it in as we go; once gm accepts a JSON file as input,
+        // we'll have to change that.
+        Json::Value expectedResults;
+        expectedResults[kJsonKey_ExpectedResults_Checksums] = expectedChecksumsArray;
+        expectedResults[kJsonKey_ExpectedResults_IgnoreFailure] = !decodedReferenceBitmap;
+        fJsonExpectedResults[name.c_str()] = expectedResults;
+
+        return retval;
     }
 
     // NOTE: As far as I can tell, this function is NEVER called with a
@@ -791,6 +837,11 @@
     // information about all failed tests we have encountered so far
     SkTArray<FailRec> fFailedTests;
 
+    Json::Value fJsonExpectedResults;
+    Json::Value fJsonActualResults_Failed;
+    Json::Value fJsonActualResults_FailureIgnored;
+    Json::Value fJsonActualResults_Succeeded;
+
 }; // end of GMMain class definition
 
 #if SK_SUPPORT_GPU
@@ -874,6 +925,7 @@
 "    [--notexturecache]: disable the gpu texture cache\n"
 "    [--tiledPipe]: Exercise tiled SkGPipe replay\n"
 "    [--tileGrid]: use a tileGrid structure for SkPicture testing\n"
+"    [--writeJsonSummary <path>]: write a JSON-formatted result summary to this file\n"
 "    [--writePath|-w <path>]: write rendered images into this directory\n"
 "    [--writePicturePath|-wp <path>]: write .skp files into this directory\n"
              );
@@ -957,6 +1009,7 @@
     setSystemPreferences();
     GMMain gmmain;
 
+    const char* writeJsonSummaryPath = NULL;// if non-null, where we write the JSON summary
     const char* writePath = NULL;   // if non-null, where we write the originals
     const char* writePicturePath = NULL;    // if non-null, where we write serialized pictures
     const char* readPath = NULL;    // if non-null, were we read from to compare
@@ -1080,6 +1133,11 @@
             if (argv < stop && **argv) {
                 writePath = *argv;
             }
+        } else if (0 == strcmp(*argv, "--writeJsonSummary")) {
+            argv++;
+            if (argv < stop && **argv) {
+                writeJsonSummaryPath = *argv;
+            }
         } else if ((0 == strcmp(*argv, "--writePicturePath")) ||
                    (0 == strcmp(*argv, "-wp"))) {
             argv++;
@@ -1351,6 +1409,22 @@
              testsRun, testsPassed, testsFailed, testsMissingReferenceImages);
     gmmain.ListErrors();
 
+    if (NULL != writeJsonSummaryPath) {
+        Json::Value actualResults;
+        actualResults[kJsonKey_ActualResults_Failed] =
+            gmmain.fJsonActualResults_Failed;
+        actualResults[kJsonKey_ActualResults_FailureIgnored] =
+            gmmain.fJsonActualResults_FailureIgnored;
+        actualResults[kJsonKey_ActualResults_Succeeded] =
+            gmmain.fJsonActualResults_Succeeded;
+        Json::Value root;
+        root[kJsonKey_ActualResults] = actualResults;
+        root[kJsonKey_ExpectedResults] = gmmain.fJsonExpectedResults;
+        std::string jsonStdString = root.toStyledString();
+        SkFILEWStream stream(writeJsonSummaryPath);
+        stream.write(jsonStdString.c_str(), jsonStdString.length());
+    }
+
 #if SK_SUPPORT_GPU
 
 #if GR_CACHE_STATS