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>
diff --git a/tests/NonlinearBlendingTest.cpp b/tests/NonlinearBlendingTest.cpp
new file mode 100644
index 0000000..10c12aa
--- /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);
+ }
+}