Adding new benchmark to test image decoding performance.

bench/SKDBench.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SKDBench.h"
+#include "SkImageDecoder.h"
+
+/*
+ *
+ * This benchmark is designed to test the performance of image decoding.
+ * It is invoked from the nanobench.cpp file.
+ *
+ */
+SKDBench::SKDBench(const char* name, SkString path, SkColorType colorType)
+    : fPath(path)
+    , fColorType(colorType) {

[scroggo, 2015/02/11 19:38:10]

I don't think we've made it official, but we've been discussing placing this
brace on its own line, so it differentiates the initialization list from the
body of the constructor.

[msarett, 2015/02/11 21:57:00]

Done.

+        fName.printf("%s_%s_%u", name, path.c_str(), colorType);

[scroggo, 2015/02/11 19:38:10]

We use indents of 4 spaces.

It looks like for decoding "resources/CMYK.jpg", we'll end up with a name like

SKD_resources/CMYK.jpg_3

?

Maybe a better name would be something like

Decode_CMYK.jpg_kN32_SkColorType (or possibly replace ".jpg" with "_jpg")

See SkOSFile.h for a method that will get the basename from the full name.

[msarett, 2015/02/11 21:57:00]

Done.

+}
+
+const char* SKDBench::onGetName() {
+    return fName.c_str();
+}
+
+bool SKDBench::isSuitableFor(Backend backend) {
+    return backend == kNonRendering_Backend;

[mtklein, 2015/02/11 19:15:36]

Seems like we might want to say this is suitable for kRaster_Backend.  Then we
can let nanobench iterate over the backend types for us (--config, e.g. 565,
8888) , instead of explicitly looping over color types specially for image
decoding.

In onDraw(), you'd call canvas->imageInfo().colorType() to get the color type to
draw.

Whether or not you actually draw it into the canvas doesn't really matter.  You
may want to draw it once (with canvas->drawBitmap()) at the end outside the
loop, just so 'nanobench -w' will work.

[scroggo, 2015/02/11 19:38:10]

That's what I did in DM, but I realized that I want to test decoding to kAlpha_8
(for some images). We don't (and can't) have an alpha 8 canvas.

[scroggo, 2015/02/11 19:38:10]

Constants should go on the left side of == (see
https://sites.google.com/site/skiadocs/developer-documentation/contributing-c...).

[msarett, 2015/02/11 21:57:00]

As discussed, we are not making this edit in order to be able to test on Alpha8
images.

[msarett, 2015/02/11 21:57:00]

Done.

[msarett, 2015/02/11 21:57:01]

Done.

+}
+    
+void SKDBench::onDraw(const int n, SkCanvas* canvas) {
+    // Decode each image file n times
+    for (int i = 0; i < n; i++) {
+        SkBitmap bitmap;
+        SkImageDecoder::DecodeFile(fPath.c_str(), &bitmap, fColorType,
+                                   SkImageDecoder::kDecodePixels_Mode);
+    }
+}