add skpdiff tool to compare bitmaps

experimental/skpdiff/SkCLImageDiffer.h

Index: experimental/skpdiff/SkCLImageDiffer.h
diff --git a/experimental/skpdiff/SkCLImageDiffer.h b/experimental/skpdiff/SkCLImageDiffer.h
new file mode 100644
index 0000000000000000000000000000000000000000..565b3714ee4101216887da0e4c5a25e384809752
--- /dev/null
+++ b/experimental/skpdiff/SkCLImageDiffer.h
@@ -0,0 +1,117 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkCLImageDiffer_DEFINED
+#define SkCLImageDiffer_DEFINED
+
+#include <CL/cl.h>
+#include "SkTDArray.h"
+
+#include "SkImageDiffer.h"
+
+class SkStream;
+
+/**
+ * An SkImageDiffer that requires initialization with an OpenCL device and context.
+ */
+class SkCLImageDiffer : public SkImageDiffer {
+public:
+    SkCLImageDiffer();
+
+    /**
+     * Initializes the OpenCL resources this differ needs to work
+     * @param  device  An OpenCL device
+     * @param  context An OpenCL context of the given device
+     * @return         True on success, false otherwise
+     */
+    virtual bool init(cl_device_id device, cl_context context);
+
+protected:
+    /**
+     * Called by init after fDevice, fContext, and fCommandQueue are successfully initialized
+     * @return True on success, false otherwise
+     */
+    virtual bool onInit() = 0;
+
+    /**
+     * Loads an OpenCL kernel from the file with the given named entry point. This only works after
+     * init is called.
+     * @param  file   The file path of the kernel
+     * @param  name   The name of the entry point of the desired kernel in the file
+     * @param  kernel A pointer to return the loaded kernel into
+     * @return        True on success, false otherwise
+     */
+    bool loadKernelFile(const char file[], const char name[], cl_kernel* kernel);
+
+    /**
+     * Loads an OpenCL kernel from the stream with the given named entry point. This only works
+     * after init is called.
+     * @param  stream  The stream that contains the kernel
+     * @param  name    The name of the entry point of the desired kernel in the stream
+     * @param  kernel  A pointer to return the loaded kernel into
+     * @return         True on success, false otherwise
+     */
+    bool loadKernelStream(SkStream* stream, const char name[], cl_kernel* kernel);
+
+    /**
+     * Loads an OpenCL kernel from the source string with the given named entry point. This only
+     * works after init is called.
+     * @param  source  The string that contains the kernel
+     * @param  name    The name of the entry point of the desired kernel in the source string
+     * @param  kernel  A pointer to return the loaded kernel into
+     * @return         True on success, false otherwise
+     */
+    bool loadKernelSource(const char source[], const char name[], cl_kernel* kernel);
+
+    /**
+     * Loads a read only copy of the given bitmap into device memory and returns the block of
+     * memory. This only works after init is called.
+     * @param  bitmap The bitmap to load into memory
+     * @param  image  A pointer to return the allocated image to
+     * @return        True on success, false otherwise
+     */
+    bool makeImage2D(SkBitmap* bitmap, cl_mem* image);
+
+    cl_device_id     fDevice;
+    cl_context       fContext;
+    cl_command_queue fCommandQueue;
+
+private:
+
+    typedef SkImageDiffer INHERITED;
+};
+
+/**
+ * A OpenCL differ that measures the percentage of different corresponding pixels. If the two images
+ * are not the same size or have no pixels, the result will always be zero.
+ */
+class SkDifferentPixelsImageDiffer : public SkCLImageDiffer {
+public:
+    virtual const char* getName() SK_OVERRIDE;
+    virtual int queueDiff(SkBitmap* baseline, SkBitmap* test) SK_OVERRIDE;
+    virtual bool isFinished(int id) SK_OVERRIDE;
+    virtual double getResult(int id) SK_OVERRIDE;
+
+protected:
+    virtual bool onInit() SK_OVERRIDE;
+
+private:
+    struct QueuedDiff {
+        bool finished;
+        double result;
+        cl_mem baseline;
+        cl_mem test;
+        cl_mem resultsBuffer;
+    };
+
+    SkTDArray<QueuedDiff> fQueuedDiffs;
+    cl_kernel fKernel;
+
+    typedef SkCLImageDiffer INHERITED;
+};
+
+#endif