Add SkICC::rawTransferFnData()

BUG=skia:

Change-Id: I912b044a0091a4d396c954d1ad1d84f5f8d50f56
Reviewed-on: https://skia-review.googlesource.com/7366
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Matt Sarett <msarett@google.com>

1 files changed, 43 insertions, 8 deletions

diff --git a/include/core/SkICC.h b/include/core/SkICC.h
index 3780498df9..04fa1dafab 100644
--- a/include/core/SkICC.h
+++ b/include/core/SkICC.h
@@ -8,6 +8,7 @@
 #ifndef SkICC_DEFINED
 #define SkICC_DEFINED
 
+#include "SkData.h"
 #include "SkRefCnt.h"
 
 struct SkColorSpaceTransferFn;
@@ -48,16 +49,48 @@ public:
     bool isNumericalTransferFn(SkColorSpaceTransferFn* fn) const;
 
     /**
-     *  If the transfer function can be approximated as coefficients to the standard
-     *  equation, returns true and sets |fn| to the proper values.
+     *  Please do not call this unless isNumericalTransferFn() has been called and it
+     *  fails.  SkColorSpaceTransferFn is the preferred representation.
      *
-     *  If not, returns false.  This indicates one of the following:
-     *  (1) The R, G, and B transfer functions are not the same.
-     *  (2) The transfer function is represented as a table that is not increasing with
-     *      end points at zero and one.
-     *  (3) The ICC data is too complex to isolate a single transfer function.
+     *  If it is not possible to represent the R, G, and B transfer functions numerically
+     *  and it is still necessary to get the transfer function, this will return the
+     *  transfer functions as three tables (R, G, and B).
+     *
+     *  If possible, this will return tables of the same length as they were specified in
+     *  the ICC profile.  This means that the lengths of the three tables are not
+     *  guaranteed to be the same.  If the ICC representation was not a table, the length
+     *  will be chosen arbitrarily.
+     *
+     *  Entries in the tables are guaranteed to be in [0, 1].
+     *
+     *  This API may be deleted in favor of a numerical approximation of the raw data.
+     *
+     *  This function may fail, indicating that the ICC profile does not have transfer
+     *  functions.
      */
-    bool approximateNumericalTransferFn(SkColorSpaceTransferFn* fn) const;
+    struct Channel {
+        // Byte offset of the start of the table in |fStorage|
+        size_t fOffset;
+        int    fCount;
+    };
+    struct Tables {
+        Channel fRed;
+        Channel fGreen;
+        Channel fBlue;
+
+        const float* red() {
+            return (const float*) (fStorage->bytes() + fRed.fOffset);
+        }
+        const float* green() {
+            return (const float*) (fStorage->bytes() + fGreen.fOffset);
+        }
+        const float* blue() {
+            return (const float*) (fStorage->bytes() + fBlue.fOffset);
+        }
+
+        sk_sp<SkData> fStorage;
+    };
+    bool rawTransferFnData(Tables* tables) const;
 
     /**
      *  Write an ICC profile with transfer function |fn| and gamut |toXYZD50|.
@@ -68,6 +101,8 @@ private:
     SkICC(sk_sp<SkColorSpace> colorSpace);
 
     sk_sp<SkColorSpace> fColorSpace;
+
+    friend class ICCTest;
 };
 
 #endif