Add gamma/sRGB tag to SkImageInfo

This reverts commit 64ba5fa1ff428858f803523257cd862f8b33423b.

BUG=skia:
R=reed@chromium.org

Author: reed@google.com

Review URL: https://codereview.chromium.org/522813002

4 files changed, 240 insertions, 46 deletions

diff --git a/gyp/tests.gypi b/gyp/tests.gypi
index c3b559e884..e4f8916637 100644
--- a/gyp/tests.gypi
+++ b/gyp/tests.gypi
@@ -119,6 +119,7 @@
     '../tests/ImageDecodingTest.cpp',
     '../tests/ImageFilterTest.cpp',
     '../tests/ImageGeneratorTest.cpp',
+    '../tests/ImageInfoTest.cpp',
     '../tests/ImageIsOpaqueTest.cpp',
     '../tests/ImageNewShaderTest.cpp',
     '../tests/InfRectTest.cpp',
diff --git a/include/core/SkImageInfo.h b/include/core/SkImageInfo.h
index 3d82dc805c..7a56fb4557 100644
--- a/include/core/SkImageInfo.h
+++ b/include/core/SkImageInfo.h
@@ -135,37 +135,50 @@ bool SkColorTypeValidateAlphaType(SkColorType colorType, SkAlphaType alphaType,
 /**
  *  Describe an image's dimensions and pixel type.
  */
-struct SkImageInfo {
+struct SK_API SkImageInfo {
+public:
+    SkImageInfo() {}
+
     int         fWidth;
     int         fHeight;
     SkColorType fColorType;
     SkAlphaType fAlphaType;
 
+    /*
+     *  Return an info with the specified attributes, tagged as sRGB. Note that if the requested
+     *  color type does not make sense with sRGB (e.g. kAlpha_8) then the sRGB request is ignored.
+     *
+     *  You can call isSRGB() on the returned info to determine if the request was fulfilled.
+     */
+    static SkImageInfo MakeSRGB(int width, int height, SkColorType ct, SkAlphaType at);
+    
+    /*
+     *  Return an info with the specified attributes, tagged with a specific gamma.
+     *  Note that if the requested gamma is unsupported for the requested color type, then the gamma
+     *  value will be set to 1.0 (the default).
+     *
+     *  You can call gamma() to query the resulting gamma value.
+     */
+    static SkImageInfo MakeWithGamma(int width, int height, SkColorType ct, SkAlphaType at,
+                                     float gamma);
+    
     static SkImageInfo Make(int width, int height, SkColorType ct, SkAlphaType at) {
-        SkImageInfo info = {
-            width, height, ct, at
-        };
-        return info;
+        return MakeWithGamma(width, height, ct, at, 1);
     }
 
     /**
      *  Sets colortype to the native ARGB32 type.
      */
     static SkImageInfo MakeN32(int width, int height, SkAlphaType at) {
-        SkImageInfo info = {
-            width, height, kN32_SkColorType, at
-        };
-        return info;
+        return SkImageInfo(width, height, kN32_SkColorType, at, kExponential_Profile, 1);
     }
 
     /**
      *  Sets colortype to the native ARGB32 type, and the alphatype to premul.
      */
     static SkImageInfo MakeN32Premul(int width, int height) {
-        SkImageInfo info = {
-            width, height, kN32_SkColorType, kPremul_SkAlphaType
-        };
-        return info;
+        return SkImageInfo(width, height, kN32_SkColorType, kPremul_SkAlphaType,
+                           kExponential_Profile, 1);
     }
 
     /**
@@ -176,24 +189,17 @@ struct SkImageInfo {
     }
 
     static SkImageInfo MakeA8(int width, int height) {
-        SkImageInfo info = {
-            width, height, kAlpha_8_SkColorType, kPremul_SkAlphaType
-        };
-        return info;
+        return SkImageInfo(width, height, kAlpha_8_SkColorType, kPremul_SkAlphaType,
+                           kUnknown_Profile, 0);
     }
 
     static SkImageInfo MakeUnknown(int width, int height) {
-        SkImageInfo info = {
-            width, height, kUnknown_SkColorType, kIgnore_SkAlphaType
-        };
-        return info;
+        return SkImageInfo(width, height, kUnknown_SkColorType, kIgnore_SkAlphaType,
+                           kUnknown_Profile, 0);
     }
 
     static SkImageInfo MakeUnknown() {
-        SkImageInfo info = {
-            0, 0, kUnknown_SkColorType, kIgnore_SkAlphaType
-        };
-        return info;
+        return SkImageInfo(0, 0, kUnknown_SkColorType, kIgnore_SkAlphaType, kUnknown_Profile, 0);
     }
 
     int width() const { return fWidth; }
@@ -236,8 +242,11 @@ struct SkImageInfo {
         return 0 != memcmp(this, &other, sizeof(other));
     }
 
+    // DEPRECATED : use the static Unflatten
     void unflatten(SkReadBuffer&);
     void flatten(SkWriteBuffer&) const;
+    
+    static SkImageInfo Unflatten(SkReadBuffer&);
 
     int64_t getSafeSize64(size_t rowBytes) const {
         if (0 == fHeight) {
@@ -256,6 +265,36 @@ struct SkImageInfo {
     }
 
     SkDEBUGCODE(void validate() const;)
+
+    /**
+     *  If the Info was tagged to be sRGB, return true, else return false.
+     */
+    bool isSRGB() const { return kSRGB_Profile == fProfile; }
+    
+    /**
+     *  If this was tagged with an explicit gamma value, return that value, else return 0.
+     *  If this was tagged as sRGB, return 0.
+     */
+    float gamma() const { return fGamma; }
+
+private:
+    enum Profile {
+        kUnknown_Profile,
+        kSRGB_Profile,
+        kExponential_Profile,
+    };
+    
+    uint32_t    fProfile;
+    float       fGamma;
+    
+    SkImageInfo(int width, int height, SkColorType ct, SkAlphaType at, Profile p, float g)
+        : fWidth(width)
+        , fHeight(height)
+        , fColorType(ct)
+        , fAlphaType(at)
+        , fProfile(p)
+        , fGamma(g)
+    {}
 };
 
 #endif
diff --git a/src/core/SkImageInfo.cpp b/src/core/SkImageInfo.cpp
index e61cd7d45f..44fd808dc8 100644
--- a/src/core/SkImageInfo.cpp
+++ b/src/core/SkImageInfo.cpp
@@ -9,34 +9,53 @@
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
 
-static bool alpha_type_is_valid(SkAlphaType alphaType) {
-    return (alphaType >= 0) && (alphaType <= kLastEnum_SkAlphaType);
+static bool color_type_supports_sRGB(SkColorType colorType) {
+    switch (colorType) {
+        case kRGBA_8888_SkColorType:
+        case kBGRA_8888_SkColorType:
+            return true;
+        default:
+            return false;
+    }
 }
 
-static bool color_type_is_valid(SkColorType colorType) {
-    return (colorType >= 0) && (colorType <= kLastEnum_SkColorType);
+static bool color_type_supports_gamma(SkColorType colorType) {
+    switch (colorType) {
+        case kRGBA_8888_SkColorType:
+        case kBGRA_8888_SkColorType:
+        // case kLuminance ...
+            return true;
+        default:
+            return false;
+    }
 }
 
-void SkImageInfo::unflatten(SkReadBuffer& buffer) {
-    fWidth = buffer.read32();
-    fHeight = buffer.read32();
-
-    uint32_t packed = buffer.read32();
-    SkASSERT(0 == (packed >> 16));
-    fAlphaType = (SkAlphaType)((packed >> 8) & 0xFF);
-    fColorType = (SkColorType)((packed >> 0) & 0xFF);
-    buffer.validate(alpha_type_is_valid(fAlphaType) &&
-                    color_type_is_valid(fColorType));
+static float pin_gamma_to_legal(float gamma) {
+    if (!SkScalarIsFinite(gamma)) {
+        return 1;
+    }
+    // these limits are just made up -- feel free to change them within reason
+    const float min_gamma = 0.01f;
+    const float max_gamma = 4.0;
+    return SkScalarPin(gamma, min_gamma, max_gamma);
 }
 
-void SkImageInfo::flatten(SkWriteBuffer& buffer) const {
-    buffer.write32(fWidth);
-    buffer.write32(fHeight);
+SkImageInfo SkImageInfo::MakeSRGB(int width, int height, SkColorType ct, SkAlphaType at) {
+    Profile p = color_type_supports_sRGB(ct) ? kSRGB_Profile : kUnknown_Profile;
+    return SkImageInfo(width, height, ct, at, p, 0);
+}
 
-    SkASSERT(0 == (fAlphaType & ~0xFF));
-    SkASSERT(0 == (fColorType & ~0xFF));
-    uint32_t packed = (fAlphaType << 8) | fColorType;
-    buffer.write32(packed);
+SkImageInfo SkImageInfo::MakeWithGamma(int width, int height, SkColorType ct, SkAlphaType at,
+                                       float gamma) {
+    Profile p;
+    if (color_type_supports_gamma(ct)) {
+        gamma = pin_gamma_to_legal(gamma);
+        p = kExponential_Profile;
+    } else {
+        p = kUnknown_Profile;
+        gamma = 0;
+    }
+    return SkImageInfo(width, height, ct, at, p, gamma);
 }
 
 bool SkColorTypeValidateAlphaType(SkColorType colorType, SkAlphaType alphaType,
@@ -69,3 +88,74 @@ bool SkColorTypeValidateAlphaType(SkColorType colorType, SkAlphaType alphaType,
     }
     return true;
 }
+
+void SkImageInfo::unflatten(SkReadBuffer& buffer) {
+    *this = Unflatten(buffer);
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////
+
+static bool alpha_type_is_valid(SkAlphaType alphaType) {
+    return (alphaType >= 0) && (alphaType <= kLastEnum_SkAlphaType);
+}
+
+static bool color_type_is_valid(SkColorType colorType) {
+    return (colorType >= 0) && (colorType <= kLastEnum_SkColorType);
+}
+
+static float igamma_to_gamma(int gamma3dot9) {
+    return gamma3dot9 / 512.0f;
+}
+
+static unsigned gamma_to_igamma(float gamma) {
+    SkASSERT(gamma >= 0 && gamma < 8);
+    int igamma = SkScalarRoundToInt(gamma * 512);
+    SkASSERT(igamma >= 0 && igamma <= 0xFFF);
+    return igamma;
+}
+
+SkImageInfo SkImageInfo::Unflatten(SkReadBuffer& buffer) {
+    int width = buffer.read32();
+    int height = buffer.read32();
+    uint32_t packed = buffer.read32();
+    
+    SkColorType ct = (SkColorType)((packed >> 0) & 0xFF);   // 8 bits for colortype
+    SkAlphaType at = (SkAlphaType)((packed >> 8) & 0xFF);   // 8 bits for alphatype
+    if (!alpha_type_is_valid(at) || !color_type_is_valid(ct)) {
+        return MakeUnknown();
+    }
+
+    // Earlier formats always stored 0 in the upper 16 bits. That corresponds to
+    // days before we had gamma/profile. That happens to correspond to kUnknown_Profile,
+    // which means we can just ignore the gamma value anyways.
+    //
+    int iprofile = ((packed >> 16) & 0xF);  // 4 bits for profile
+    
+    switch (iprofile) {
+        case kUnknown_Profile:
+            return Make(width, height, ct, at);
+        case kSRGB_Profile:
+            return MakeSRGB(width, height, ct, at);
+        case kExponential_Profile: {
+            int igamma = packed >> 20;      // 12 bits for gamma 3.9
+            float gamma = igamma_to_gamma(igamma);
+            return MakeWithGamma(width, height, ct, at, gamma);
+        }
+        default:
+            (void)buffer.validate(false);
+            return MakeUnknown();
+    }
+}
+
+void SkImageInfo::flatten(SkWriteBuffer& buffer) const {
+    buffer.write32(fWidth);
+    buffer.write32(fHeight);
+    
+    SkASSERT(0 == (fColorType & ~0xFF));    // 8 bits for colortype
+    SkASSERT(0 == (fAlphaType & ~0xFF));    // 8 bits for alphatype
+    SkASSERT(0 == (fProfile & ~0xF));       // 4 bits for profile
+    int igamma = gamma_to_igamma(fGamma);   // 12 bits for gamma (if needed)
+ 
+    uint32_t packed = (igamma << 20) | (fProfile << 16) | (fAlphaType << 8) | fColorType;
+    buffer.write32(packed);
+}
diff --git a/tests/ImageInfoTest.cpp b/tests/ImageInfoTest.cpp
new file mode 100644
index 0000000000..679b302ceb
--- /dev/null
+++ b/tests/ImageInfoTest.cpp
@@ -0,0 +1,64 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkImageInfo.h"
+
+#include "Test.h"
+
+struct ImageInfoRec {
+    int         fWidth;
+    int         fHeight;
+    SkColorType fColorType;
+    SkAlphaType fAlphaType;
+    float       fGamma;
+    bool        fIsSRGB;
+};
+
+static void check_info(skiatest::Reporter* reporter,
+                       const ImageInfoRec& expected, const SkImageInfo& info) {
+    REPORTER_ASSERT(reporter, info.width() == expected.fWidth);
+    REPORTER_ASSERT(reporter, info.height() == expected.fHeight);
+    REPORTER_ASSERT(reporter, info.colorType() == expected.fColorType);
+    REPORTER_ASSERT(reporter, info.alphaType() == expected.fAlphaType);
+    REPORTER_ASSERT(reporter, info.gamma() == expected.fGamma);
+    REPORTER_ASSERT(reporter, info.isSRGB() == expected.fIsSRGB);
+}
+
+DEF_TEST(ImageInfo, reporter) {
+    const float nan = SK_ScalarNaN;
+    const float nice_gamma = 1.5f;
+    const int W = 100;
+    const int H = 200;
+    SkImageInfo info;
+    
+    const ImageInfoRec rec[] = {
+        { 0, 0, kUnknown_SkColorType,   kIgnore_SkAlphaType,   0, false },  // MakeUnknown()
+        { W, H, kUnknown_SkColorType,   kIgnore_SkAlphaType,   0, false },  // MakeUnknown(...)
+        { W, H, kN32_SkColorType,       kPremul_SkAlphaType,   1, false },  // MakeN32Premul(...)
+        { W, H, kN32_SkColorType,       kOpaque_SkAlphaType,   1, false },  // MakeN32(...)
+        { W, H, kAlpha_8_SkColorType,   kPremul_SkAlphaType,   0, false },  // MakeA8()
+        { W, H, kRGBA_8888_SkColorType, kUnpremul_SkAlphaType, 1, false },  // Make()
+        { W, H, kBGRA_8888_SkColorType, kPremul_SkAlphaType,   1, false },  // Make()
+        { W, H, kBGRA_8888_SkColorType, kPremul_SkAlphaType,   0, true },  // MakeSRGB()
+        { W, H, kN32_SkColorType,       kPremul_SkAlphaType,   1, false },  // MakeWithGamma() NaN
+        { W, H, kAlpha_8_SkColorType,   kPremul_SkAlphaType,   0, false },  // MakeWithGamma() bad ct for gamma
+        { W, H, kN32_SkColorType,       kPremul_SkAlphaType,   nice_gamma, false },  // MakeWithGamma() good
+    };
+
+    check_info(reporter, rec[ 0], SkImageInfo::MakeUnknown());
+    check_info(reporter, rec[ 1], SkImageInfo::MakeUnknown(W, H));
+    check_info(reporter, rec[ 2], SkImageInfo::MakeN32Premul(W, H));
+    check_info(reporter, rec[ 3], SkImageInfo::MakeN32(W, H, rec[3].fAlphaType));
+    check_info(reporter, rec[ 4], SkImageInfo::MakeA8(W, H));
+    check_info(reporter, rec[ 5], SkImageInfo::Make(W, H, rec[5].fColorType, rec[5].fAlphaType));
+    check_info(reporter, rec[ 6], SkImageInfo::Make(W, H, rec[6].fColorType, rec[6].fAlphaType));
+    check_info(reporter, rec[ 7], SkImageInfo::MakeSRGB(W, H, rec[7].fColorType, rec[7].fAlphaType));
+    check_info(reporter, rec[ 8], SkImageInfo::MakeWithGamma(W, H, rec[8].fColorType, rec[8].fAlphaType, nan));
+    check_info(reporter, rec[ 9], SkImageInfo::MakeWithGamma(W, H, rec[9].fColorType, rec[9].fAlphaType, nice_gamma));
+    check_info(reporter, rec[10], SkImageInfo::MakeWithGamma(W, H, rec[10].fColorType, rec[10].fAlphaType, rec[10].fGamma));
+}
+