Added --deepColor option to SampleApp, triggers creation of a ten-bit/channel buffer on Windows.

tests/ApplyGammaTest.cpp

Index: tests/ApplyGammaTest.cpp
diff --git a/tests/ApplyGammaTest.cpp b/tests/ApplyGammaTest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..396ce60bef76fb23756a8ae8a04c2a4ae3b1c63b
--- /dev/null
+++ b/tests/ApplyGammaTest.cpp
@@ -0,0 +1,157 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include <initializer_list>
+#include "Test.h"
+
+#if SK_SUPPORT_GPU
+#include "GrContext.h"
+#include "GrTexture.h"
+#include "GrTextureProvider.h"
+
+#include "SkUtils.h"
+
+ // using anonymous namespace because these functions are used as template params.
+namespace {
+/** convert 0..1 linear value to 0..1 srgb */
+float linear_to_srgb(float linear) {
+    if (linear <= 0.0031308) {
+        return linear * 12.92f;
+    } else {
+        return 1.055f * powf(linear, 1.f / 2.4f) - 0.055f;
+    }
+}
+}
+
+bool check_gamma(uint32_t src, uint32_t dst, float gamma, float error, uint32_t* expected) {
+    if (SkScalarNearlyEqual(gamma, 1.f)) {
+        *expected = src;
+        return src == dst;
+    } else {
+        bool result = true;
+        uint32_t expectedColor = src & 0xff000000;
+
+        // Alpha should always be exactly preserved.
+        if ((src & 0xff000000) != (dst & 0xff000000)) {
+            result = false;
+        }
+
+        for (int c = 0; c < 3; ++c) {
+            uint8_t srcComponent = (src & (0xff << (c * 8))) >> (c * 8);
+            float lower = SkTMax(0.f, (float)srcComponent - error);
+            float upper = SkTMin(255.f, (float)srcComponent + error);
+            if (SkScalarNearlyEqual(gamma, 2.2f)) {
+                lower = linear_to_srgb(lower / 255.f);
+                upper = linear_to_srgb(upper / 255.f);
+            } else {
+                float invGamma = 1.f / gamma;
+                lower = powf(lower / 255.f, invGamma);
+                upper = powf(upper / 255.f, invGamma);
+            }
+            SkASSERT(lower >= 0.f && lower <= 255.f);
+            SkASSERT(upper >= 0.f && upper <= 255.f);
+            uint8_t dstComponent = (dst & (0xff << (c * 8))) >> (c * 8);
+            if (dstComponent < SkScalarFloorToInt(lower * 255.f) ||
+                dstComponent > SkScalarCeilToInt(upper * 255.f)) {
+                result = false;
+            }
+            uint8_t expectedComponent = SkScalarRoundToInt((lower + upper) * 127.5f);
+            expectedColor |= expectedComponent << (c * 8);
+        }
+
+        *expected = expectedColor;
+        return result;
+    }
+}
+
+DEF_GPUTEST_FOR_RENDERING_CONTEXTS(ApplyGamma, reporter, ctxInfo) {
+    GrContext* context = ctxInfo.fGrContext;
+    static const int kW = 10;
+    static const int kH = 10;
+    static const size_t kRowBytes = sizeof(uint32_t) * kW;
+
+    GrSurfaceDesc baseDesc;
+    baseDesc.fConfig = kRGBA_8888_GrPixelConfig;
+    baseDesc.fWidth = kW;
+    baseDesc.fHeight = kH;
+
+    SkAutoTMalloc<uint32_t> srcPixels(kW * kH);
+    for (int i = 0; i < kW * kH; ++i) {
+        srcPixels.get()[i] = i;
+    }
+
+    SkAutoTMalloc<uint32_t> dstPixels(kW * kH);
+    for (int i = 0; i < kW * kH; ++i) {
+        dstPixels.get()[i] = ~i;
+    }
+
+    SkAutoTMalloc<uint32_t> read(kW * kH);
+
+    // We allow more error on GPUs with lower precision shader variables.
+    float error = context->caps()->shaderCaps()->floatPrecisionVaries() ? 1.2f : 0.5f;
+
+    for (auto sOrigin : { kBottomLeft_GrSurfaceOrigin, kTopLeft_GrSurfaceOrigin }) {
+        for (auto dOrigin : { kBottomLeft_GrSurfaceOrigin, kTopLeft_GrSurfaceOrigin }) {
+            for (auto sFlags : { kRenderTarget_GrSurfaceFlag, kNone_GrSurfaceFlags }) {
+                for (auto gamma : { 1.0f, 1.8f, 2.2f }) {

[Brian Osman, 2016/05/02 21:02:45]

Tests identity, sRGB and arbitrary gamma (to exercise every code path).

+                    GrSurfaceDesc srcDesc = baseDesc;
+                    srcDesc.fOrigin = sOrigin;
+                    srcDesc.fFlags = sFlags;
+                    GrSurfaceDesc dstDesc = baseDesc;
+                    dstDesc.fOrigin = dOrigin;
+                    dstDesc.fFlags = kRenderTarget_GrSurfaceFlag;
+
+                    SkAutoTUnref<GrTexture> src(
+                        context->textureProvider()->createTexture(srcDesc, SkBudgeted::kNo,
+                                                                  srcPixels.get(),
+                                                                  kRowBytes));
+                    SkAutoTUnref<GrTexture> dst(
+                        context->textureProvider()->createTexture(dstDesc, SkBudgeted::kNo,
+                                                                  dstPixels.get(),
+                                                                  kRowBytes));
+                    if (!src || !dst) {
+                        ERRORF(reporter, "Could not create surfaces for copy surface test.");
+                        continue;
+                    }
+
+                    bool result = context->applyGamma(dst->asRenderTarget(), src, gamma);
+
+                    // To make the copied src rect correct we would apply any dst clipping
+                    // back to the src rect, but we don't use it again so don't bother.
+                    if (!result) {
+                        ERRORF(reporter, "Unexpected failure from applyGamma.");
+                        continue;
+                    }
+
+                    sk_memset32(read.get(), 0, kW * kH);
+                    if (!dst->readPixels(0, 0, kW, kH, baseDesc.fConfig, read.get(), kRowBytes)) {
+                        ERRORF(reporter, "Error calling readPixels");
+                        continue;
+                    }
+
+                    bool abort = false;
+                    // Validate that pixels were copied/transformed correctly.
+                    for (int y = 0; y < kH && !abort; ++y) {
+                        for (int x = 0; x < kW && !abort; ++x) {
+                            uint32_t r = read.get()[y * kW + x];
+                            uint32_t s = srcPixels.get()[y * kW + x];
+                            uint32_t expected;
+                            if (!check_gamma(s, r, gamma, error, &expected)) {
+                                ERRORF(reporter, "Expected dst %d,%d to contain 0x%08x "
+                                       "from src 0x%08x and gamma %f. Got %08x",
+                                       x, y, expected, s, gamma, r);
+                                abort = true;
+                                break;
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+#endif