Move SkPngEncoder into public API

Bug: 713862
Change-Id: I45068ed39affe41ffe0f29bf42c5ea1d9b0247ba
Reviewed-on: https://skia-review.googlesource.com/15897
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Matt Sarett <msarett@google.com>

2 files changed, 139 insertions, 0 deletions

diff --git a/include/encode/SkEncoder.h b/include/encode/SkEncoder.h
new file mode 100644
index 0000000000..d1b99fd5af
--- /dev/null
+++ b/include/encode/SkEncoder.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkEncoder_DEFINED
+#define SkEncoder_DEFINED
+
+#include "SkPixmap.h"
+#include "../private/SkTemplates.h"
+
+class SkEncoder : SkNoncopyable {
+public:
+
+    /**
+     *  Encode |numRows| rows of input.  If the caller requests more rows than are remaining
+     *  in the src, this will encode all of the remaining rows.  |numRows| must be greater
+     *  than zero.
+     */
+    bool encodeRows(int numRows);
+
+    virtual ~SkEncoder() {}
+
+protected:
+
+    virtual bool onEncodeRows(int numRows) = 0;
+
+    SkEncoder(const SkPixmap& src, size_t storageBytes)
+        : fSrc(src)
+        , fCurrRow(0)
+        , fStorage(storageBytes)
+    {}
+
+    const SkPixmap&        fSrc;
+    int                    fCurrRow;
+    SkAutoTMalloc<uint8_t> fStorage;
+};
+
+#endif
diff --git a/include/encode/SkPngEncoder.h b/include/encode/SkPngEncoder.h
new file mode 100644
index 0000000000..adcc061113
--- /dev/null
+++ b/include/encode/SkPngEncoder.h
@@ -0,0 +1,98 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkPngEncoder_DEFINED
+#define SkPngEncoder_DEFINED
+
+#include "SkEncoder.h"
+
+class SkPngEncoderMgr;
+class SkWStream;
+
+class SK_API SkPngEncoder : public SkEncoder {
+public:
+
+    enum class FilterFlag : int {
+        kZero  = 0x00,
+        kNone  = 0x08,
+        kSub   = 0x10,
+        kUp    = 0x20,
+        kAvg   = 0x40,
+        kPaeth = 0x80,
+        kAll   = kNone | kSub | kUp | kAvg | kPaeth,
+    };
+
+    struct Options {
+        /**
+         *  Selects which filtering strategies to use.
+         *
+         *  If a single filter is chosen, libpng will use that filter for every row.
+         *
+         *  If multiple filters are chosen, libpng will use a heuristic to guess which filter
+         *  will encode smallest, then apply that filter.  This happens on a per row basis,
+         *  different rows can use different filters.
+         *
+         *  Using a single filter (or less filters) is typically faster.  Trying all of the
+         *  filters may help minimize the output file size.
+         *
+         *  Our default value matches libpng's default.
+         */
+        FilterFlag fFilterFlags = FilterFlag::kAll;
+
+        /**
+         *  Must be in [0, 9] where 9 corresponds to maximal compression.  This value is passed
+         *  directly to zlib.  0 is a special case to skip zlib entirely, creating dramatically
+         *  larger pngs.
+         *
+         *  Our default value matches libpng's default.
+         */
+        int fZLibLevel = 6;
+
+        /**
+         *  If the input is premultiplied, this controls the unpremultiplication behavior.
+         *  The encoder can convert to linear before unpremultiplying or ignore the transfer
+         *  function and unpremultiply the input as is.
+         */
+        SkTransferFunctionBehavior fUnpremulBehavior = SkTransferFunctionBehavior::kRespect;
+    };
+
+    /**
+     *  Encode the |src| pixels to the |dst| stream.
+     *  |options| may be used to control the encoding behavior.
+     *
+     *  Returns true on success.  Returns false on an invalid or unsupported |src|.
+     */
+    static bool Encode(SkWStream* dst, const SkPixmap& src, const Options& options);
+
+    /**
+     *  Create a png encoder that will encode the |src| pixels to the |dst| stream.
+     *  |options| may be used to control the encoding behavior.
+     *
+     *  |dst| is unowned but must remain valid for the lifetime of the object.
+     *
+     *  This returns nullptr on an invalid or unsupported |src|.
+     */
+    static std::unique_ptr<SkPngEncoder> Make(SkWStream* dst, const SkPixmap& src,
+                                               const Options& options);
+
+    ~SkPngEncoder() override;
+
+protected:
+    bool onEncodeRows(int numRows) override;
+
+    SkPngEncoder(std::unique_ptr<SkPngEncoderMgr>, const SkPixmap& src);
+
+    std::unique_ptr<SkPngEncoderMgr> fEncoderMgr;
+    typedef SkEncoder INHERITED;
+};
+
+static inline SkPngEncoder::FilterFlag operator|(SkPngEncoder::FilterFlag x,
+                                                 SkPngEncoder::FilterFlag y) {
+    return (SkPngEncoder::FilterFlag)((int)x | (int)y);
+}
+
+#endif