Updates to images project.

Use the SkImageEncoder_Factory on all platforms. On Windows and Mac,
register the platform's image encoder as an option for
SkImageEncoder::Create. Also add more types that can be decoded.

Update comments for SkImageDecoder to be more accurate.

Add more types to SkImageEncoder::Type, and return the correct type of
encoder, if it exists.

Use a custom version of SkImageDecoder::Factory on Windows and Mac to
check the stream for registered decoders before defaulting to the platform's
version. Share code with the existing SkImageDecoder::Factory method.

Preparation for testing decoders and encoders:
BUG=https://code.google.com/p/skia/issues/detail?id=1241

Review URL: https://codereview.chromium.org/14298010

git-svn-id: http://skia.googlecode.com/svn/trunk@8730 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 47 insertions, 0 deletions

diff --git a/src/images/SkImageDecoder_FactoryRegistrar.cpp b/src/images/SkImageDecoder_FactoryRegistrar.cpp
new file mode 100644
index 0000000000..6cc417a46f
--- /dev/null
+++ b/src/images/SkImageDecoder_FactoryRegistrar.cpp
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2013 The Android Open Source Project
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkImageDecoder.h"
+#include "SkStream.h"
+#include "SkTRegistry.h"
+
+// This file is used for registration of SkImageDecoders. It also holds a function
+// for checking all the the registered SkImageDecoders for one that matches an
+// input SkStream.
+
+typedef SkTRegistry<SkImageDecoder*, SkStream*> DecodeReg;
+
+// N.B. You can't use "DecodeReg::gHead here" due to complex C++
+// corner cases.
+template DecodeReg* SkTRegistry<SkImageDecoder*, SkStream*>::gHead;
+
+SkImageDecoder* image_decoder_from_stream(SkStream*);
+
+SkImageDecoder* image_decoder_from_stream(SkStream* stream) {
+    SkImageDecoder* codec = NULL;
+    const DecodeReg* curr = DecodeReg::Head();
+    while (curr) {
+        codec = curr->factory()(stream);
+        // we rewind here, because we promise later when we call "decode", that
+        // the stream will be at its beginning.
+        bool rewindSuceeded = stream->rewind();
+
+        // our image decoder's require that rewind is supported so we fail early
+        // if we are given a stream that does not support rewinding.
+        if (!rewindSuceeded) {
+            SkDEBUGF(("Unable to rewind the image stream."));
+            SkDELETE(codec);
+            return NULL;
+        }
+
+        if (codec) {
+            return codec;
+        }
+        curr = curr->next();
+    }
+    return NULL;
+}