PDF: Add (low-memory) SkPDFBitmap class

src/pdf/SkPDFBitmap.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#ifndef SkPDFBitmap_DEFINED
+#define SkPDFBitmap_DEFINED
+
+#include "SkPDFTypes.h"
+#include "SkBitmap.h"
+
+/**
+ * SkPDFBitmap wraps a SkBitmap and serializes it as an image Xobject.
+ * It is designed to use a minimal amout of memory, aside from refing
+ * the bitmap's pixels, and its emitObject() does not cache any data.
+ *
+ * As of now, it only supports 8888 bitmaps (the most common case).
+ *
+ * The SkPDFBitmap::Create function will check the canon for duplicates.
+ */
+class SkPDFBitmap : public SkPDFObject {
+public:
+    // Returns NULL on unsupported bitmap;
+    // TODO(halcanary): support other bitmap colortypes and replace
+    // SkPDFImage.
+    static SkPDFBitmap* Create(const SkBitmap&, const SkIRect& subset);
+    ~SkPDFBitmap();
+    void emitObject(SkWStream*, SkPDFCatalog*) SK_OVERRIDE;
+    void addResources(SkTSet<SkPDFObject*>* resourceSet,
+                      SkPDFCatalog* catalog) const SK_OVERRIDE;
+    bool equals(const SkBitmap& other) const {
+        return fBitmap.getGenerationID() == other.getGenerationID() &&
+               fBitmap.pixelRefOrigin() == other.pixelRefOrigin() &&
+               fBitmap.dimensions() == other.dimensions();
+    }
+
+private:
+    const SkBitmap fBitmap;
+    const SkAutoTUnref<SkPDFObject> fSMask;
+    SkPDFBitmap(const SkBitmap&, SkPDFObject*);
+    void emitDict(SkWStream*, SkPDFCatalog*, size_t, bool) const;
+};
+
+#endif  // SkPDFBitmap_DEFINED