non-linear blending first steps

Code:
  - Add a non-linear blending bit and makeNonlinearBlending()
    to SkColorSpace
  - remove enough F16=linear checks to make it possible to
    create surfaces and encode pngs with nonlinear F16

Testing:
  - add "esrgb" software config to DM, run it
  - add "srgbnl" software config, run it
  - deemphasize importance of "srgb" config on bots
  - update unit tests to reflect relaxed F16 constraints
  - add a new unit test file with _really_ basic tests,
    and a new unit test that's not working yet

Bug: skia:7942

Change-Id: I8ac042bdf9f3d791765393b68fd9256375184d83
Reviewed-on: https://skia-review.googlesource.com/127325
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

3 files changed, 83 insertions, 7 deletions

diff --git a/tests/CodecTest.cpp b/tests/CodecTest.cpp
index ceb10a10df..474cdc6931 100644
--- a/tests/CodecTest.cpp
+++ b/tests/CodecTest.cpp
@@ -1144,22 +1144,22 @@ static void test_conversion_possible(skiatest::Reporter* r, const char* path,
     SkBitmap bm;
     bm.allocPixels(infoF16);
     SkCodec::Result result = codec->getPixels(infoF16, bm.getPixels(), bm.rowBytes());
-    REPORTER_ASSERT(r, SkCodec::kInvalidConversion == result);
+    REPORTER_ASSERT(r, SkCodec::kSuccess == result);
 
     result = codec->startScanlineDecode(infoF16);
     if (supportsScanlineDecoder) {
-        REPORTER_ASSERT(r, SkCodec::kInvalidConversion == result);
+        REPORTER_ASSERT(r, SkCodec::kSuccess == result);
     } else {
         REPORTER_ASSERT(r, SkCodec::kUnimplemented == result
-                        || SkCodec::kInvalidConversion == result);
+                        || SkCodec::kSuccess == result);
     }
 
     result = codec->startIncrementalDecode(infoF16, bm.getPixels(), bm.rowBytes());
     if (supportsIncrementalDecoder) {
-        REPORTER_ASSERT(r, SkCodec::kInvalidConversion == result);
+        REPORTER_ASSERT(r, SkCodec::kSuccess == result);
     } else {
         REPORTER_ASSERT(r, SkCodec::kUnimplemented == result
-                        || SkCodec::kInvalidConversion == result);
+                        || SkCodec::kSuccess == result);
     }
 
     infoF16 = infoF16.makeColorSpace(infoF16.colorSpace()->makeLinearGamma());
diff --git a/tests/NonlinearBlendingTest.cpp b/tests/NonlinearBlendingTest.cpp
new file mode 100644
index 0000000000..10c12aa280
--- /dev/null
+++ b/tests/NonlinearBlendingTest.cpp
@@ -0,0 +1,76 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "Test.h"
+#include "SkHalf.h"
+#include "SkSurface.h"
+#include "SkCanvas.h"
+
+DEF_TEST(NonlinearBlending, r) {
+
+    // First check our familiar basics with linear F16.
+    {
+        auto info = SkImageInfo::Make(1,1, kRGBA_F16_SkColorType, kPremul_SkAlphaType,
+                                      SkColorSpace::MakeSRGBLinear());
+
+        auto surface = SkSurface::MakeRaster(info);
+        surface->getCanvas()->clear(0xff808080);
+        uint64_t pix;
+        REPORTER_ASSERT(r, surface->readPixels(info, &pix, sizeof(pix),0,0));
+
+        // 0x80 in sRGB is ≈ 0.22 linear.
+        REPORTER_ASSERT(r, SkHalfToFloat(pix & 0xffff) < 0.25f);
+    }
+
+    // Test that we support sRGB-encoded F16.  This is somewhat new.
+    {
+        auto info = SkImageInfo::Make(1,1, kRGBA_F16_SkColorType, kPremul_SkAlphaType,
+                                      SkColorSpace::MakeSRGB());
+
+        auto surface = SkSurface::MakeRaster(info);
+        surface->getCanvas()->clear(0xff808080);
+        uint64_t pix;
+        REPORTER_ASSERT(r, surface->readPixels(info, &pix, sizeof(pix),0,0));
+
+        // 0x80 sRGB is ≈ 0.501.
+        REPORTER_ASSERT(r, SkHalfToFloat(pix & 0xffff) >= 0.5f);
+    }
+
+    // Since we're only clear()ing, this should work the same as the last block.
+    {
+        auto info = SkImageInfo::Make(1,1, kRGBA_F16_SkColorType, kPremul_SkAlphaType,
+                                      SkColorSpace::MakeSRGB()->makeNonlinearBlending());
+
+        auto surface = SkSurface::MakeRaster(info);
+        surface->getCanvas()->clear(0xff808080);
+        uint64_t pix;
+        REPORTER_ASSERT(r, surface->readPixels(info, &pix, sizeof(pix),0,0));
+
+        // 0x80 sRGB is ≈ 0.501.
+        REPORTER_ASSERT(r, SkHalfToFloat(pix & 0xffff) >= 0.5f);
+    }
+
+    // This won't work until we actually support color spaces with non-linear blending.
+    if (0) {
+        auto info = SkImageInfo::Make(1,1, kRGBA_F16_SkColorType, kPremul_SkAlphaType,
+                                      SkColorSpace::MakeSRGB()->makeNonlinearBlending());
+
+        auto surface = SkSurface::MakeRaster(info);
+
+        surface->getCanvas()->clear(SK_ColorWHITE);
+        SkPaint p;
+        p.setColor(0x80000000);
+        surface->getCanvas()->drawPaint(p);
+
+        uint64_t pix;
+        REPORTER_ASSERT(r, surface->readPixels(info, &pix, sizeof(pix),0,0));
+
+        // 0x80 sRGB is ≈ 0.501.  A likely failure here is ~0.75, linear blending.
+        REPORTER_ASSERT(r, SkHalfToFloat(pix & 0xffff) >= 0.45f &&
+                           SkHalfToFloat(pix & 0xffff) <= 0.55f);
+    }
+}
diff --git a/tests/SurfaceTest.cpp b/tests/SurfaceTest.cpp
index 835e9ffc7f..e757230aa1 100644
--- a/tests/SurfaceTest.cpp
+++ b/tests/SurfaceTest.cpp
@@ -951,8 +951,8 @@ static void test_surface_creation_and_snapshot_with_color_space(
         { kN32_SkColorType,       oddColorSpace,    false, "N32-odd"     },
         { kRGBA_F16_SkColorType,  nullptr,          true,  "F16-nullptr" },
         { kRGBA_F16_SkColorType,  linearColorSpace, true,  "F16-linear"  },
-        { kRGBA_F16_SkColorType,  srgbColorSpace,   false, "F16-srgb"    },
-        { kRGBA_F16_SkColorType,  oddColorSpace,    false, "F16-odd"     },
+        { kRGBA_F16_SkColorType,  srgbColorSpace,   true,  "F16-srgb"    },
+        { kRGBA_F16_SkColorType,  oddColorSpace,    true,  "F16-odd"     },
         { kRGB_565_SkColorType,   srgbColorSpace,   false, "565-srgb"    },
         { kAlpha_8_SkColorType,   srgbColorSpace,   false, "A8-srgb"     },
         { kRGBA_1010102_SkColorType, nullptr,       true,  "1010102-nullptr" },