add --readJsonSummaryPath to render_pictures

tools/image_expectations.h

Index: tools/image_expectations.h
diff --git a/tools/image_expectations.h b/tools/image_expectations.h
index 432cf6d3a80bd3f4cbe2e563c2c0d4116a47d7a5..09a945a1b013b05e4ed874e36efb29ae009892e5 100644
--- a/tools/image_expectations.h
+++ b/tools/image_expectations.h
@@ -10,34 +10,89 @@
 
 #include "SkBitmap.h"
 #include "SkJSONCPP.h"
+#include "SkRefCnt.h"
 
 namespace sk_tools {
 
     /**
-     * Class for collecting image results (checksums) as we go.
+     * The digest of an image (either an image we have generated locally, or an image expectation).
+     *
+     * Currently, this is always a uint64_t hash digest of an SkBitmap.
      */
-    class ImageResultsSummary {
+    class ImageDigest : public SkRefCnt {
     public:
         /**
-         * Adds this image to the summary of results.
+         * Create an ImageDigest of a bitmap.
          *
-         * @param sourceName name of the source file that generated this result
-         * @param fileName relative path to the image output file on local disk
-         * @param hash hash to store
-         * @param tileNumber if not NULL, ptr to tile number
+         * Note that this is an expensive operation, because it has to examine all pixels in
+         * the bitmap.  You may wish to consider using the BitmapAndDigest class, which will
+         * compute the ImageDigest lazily.
+         *
+         * @param bitmap image to get the digest of
          */
-        void add(const char *sourceName, const char *fileName, uint64_t hash,
-                 const int *tileNumber=NULL);
+        explicit ImageDigest(const SkBitmap &bitmap);
+
+        /**
+         * Create an ImageDigest using a hashType/hashValue pair.
+         *
+         * @param hashType the algorithm used to generate the hash; for now, only
+         *     kJsonValue_Image_ChecksumAlgorithm_Bitmap64bitMD5 is allowed.
+         * @param hashValue the value generated by the hash algorithm for a particular image.
+         */
+        explicit ImageDigest(const SkString &hashType, uint64_t hashValue);
+
+        /**
+         * Returns the hash digest type as an SkString.
+         *
+         * For now, this always returns kJsonValue_Image_ChecksumAlgorithm_Bitmap64bitMD5 .
+         */
+        SkString getHashType() const;
+
+        /**
+         * Returns the hash digest value as a uint64_t.
+         */
+        uint64_t getHashValue() const;
+
+    private:
+        uint64_t fHashValue;
+    };
+
+    /**
+     * Container that holds a reference to an SkBitmap and computes its ImageDigest lazily.
+     *
+     * Computing the ImageDigest can be expensive, so this can help you postpone (or maybe even
+     * avoid) that work.
+     */
+    class BitmapAndDigest {
+    public:
+        explicit BitmapAndDigest(const SkBitmap &bitmap);
+
+        const ImageDigest *getImageDigestPtr();
+        const SkBitmap *getBitmapPtr() const;
+    private:
+        const SkBitmap fBitmap;
+        SkAutoTUnref<ImageDigest> fImageDigestRef;
+    };
+
+    /**
+     * Collects ImageDigests of actually rendered images, perhaps comparing to expectations.
+     */
+    class ImageResultsAndExpectations {
+    public:
+        /**
+         * Adds expectations from a JSON file, returning true if successful.
+         */
+        bool readExpectationsFile(const char *jsonPath);
 
         /**
          * Adds this image to the summary of results.
          *
          * @param sourceName name of the source file that generated this result
          * @param fileName relative path to the image output file on local disk
-         * @param bitmap bitmap to store the hash of
+         * @param digest description of the image's contents
          * @param tileNumber if not NULL, ptr to tile number
          */
-        void add(const char *sourceName, const char *fileName, const SkBitmap& bitmap,
+        void add(const char *sourceName, const char *fileName, const ImageDigest &digest,
                  const int *tileNumber=NULL);
 
         /**
@@ -45,10 +100,20 @@ namespace sk_tools {
          *
          * @param filename path to write the summary to
          */
-        void writeToFile(const char *filename);
+        void writeToFile(const char *filename) const;
 
     private:
+
+        /**
+         * Read the file contents from jsonPath and parse them into jsonRoot.
+         *
+         * Returns true if successful.
+         */
+        static bool Parse(const char *jsonPath, Json::Value *jsonRoot);
+
         Json::Value fActualResults;
+        Json::Value fExpectedJsonRoot;
+        Json::Value fExpectedResults;
     };
 
 } // namespace sk_tools