implement readPixels and writePixels natively, w/o using the (deprecated)

include/core/SkColorPriv.h

Index: include/core/SkColorPriv.h
diff --git a/include/core/SkColorPriv.h b/include/core/SkColorPriv.h
index 7a74c4a034b24a079504fd790a92bcd67014f73f..9591f22725a81289059a04bb82bddc79c849cc25 100644
--- a/include/core/SkColorPriv.h
+++ b/include/core/SkColorPriv.h
@@ -1,4 +1,3 @@
-
 /*
  * Copyright 2006 The Android Open Source Project
  *
@@ -6,7 +5,6 @@
  * found in the LICENSE file.
  */
 
-
 #ifndef SkColorPriv_DEFINED
 #define SkColorPriv_DEFINED
 
@@ -18,6 +16,134 @@
 #include "SkColor.h"
 #include "SkMath.h"
 
+//////////////////////////////////////////////////////////////////////////////
+
+#define SkASSERT_IS_BYTE(x)     SkASSERT(0 == ((x) & ~0xFF))
+
+/*
+ *  Skia's 32bit backend only supports 1 sizzle order at a time (compile-time).
+ *  This is specified by 4 defines SK_A32_SHIFT, SK_R32_SHIFT, ... for G and B.
+ *
+ *  For easier compatibility with Skia's GPU backend, we further restrict these
+ *  to either (in memory-byte-order) RGBA or BGRA. Note that this "order" does
+ *  not directly correspond to the same shift-order, since we have to take endianess
+ *  into account.
+ *
+ *  Here we enforce this constraint.
+ */
+
+#ifdef SK_CPU_BENDIAN
+    #define SK_RGBA_R32_SHIFT   24
+    #define SK_RGBA_G32_SHIFT   16
+    #define SK_RGBA_B32_SHIFT   8
+    #define SK_RGBA_A32_SHIFT   0
+
+    #define SK_BGRA_B32_SHIFT   24
+    #define SK_BGRA_G32_SHIFT   16
+    #define SK_BGRA_R32_SHIFT   8
+    #define SK_BGRA_A32_SHIFT   0
+#else
+    #define SK_RGBA_R32_SHIFT   0
+    #define SK_RGBA_G32_SHIFT   8
+    #define SK_RGBA_B32_SHIFT   16
+    #define SK_RGBA_A32_SHIFT   24
+
+    #define SK_BGRA_B32_SHIFT   0
+    #define SK_BGRA_G32_SHIFT   8
+    #define SK_BGRA_R32_SHIFT   16
+    #define SK_BGRA_A32_SHIFT   24
+#endif
+
+#if defined(SK_PMCOLOR_IS_RGBA) && defined(SK_PMCOLOR_IS_BGRA)
+    #error "can't define PMCOLOR to be RGBA and BGRA"
+#endif
+
+#define LOCAL_PMCOLOR_SHIFTS_EQUIVALENT_TO_RGBA  \
+    (SK_A32_SHIFT == SK_RGBA_A32_SHIFT &&    \
+     SK_R32_SHIFT == SK_RGBA_R32_SHIFT &&    \
+     SK_G32_SHIFT == SK_RGBA_G32_SHIFT &&    \
+     SK_B32_SHIFT == SK_RGBA_B32_SHIFT)
+
+#define LOCAL_PMCOLOR_SHIFTS_EQUIVALENT_TO_BGRA  \
+    (SK_A32_SHIFT == SK_BGRA_A32_SHIFT &&    \
+     SK_R32_SHIFT == SK_BGRA_R32_SHIFT &&    \
+     SK_G32_SHIFT == SK_BGRA_G32_SHIFT &&    \
+     SK_B32_SHIFT == SK_BGRA_B32_SHIFT)
+
+
+#if defined(SK_PMCOLOR_IS_RGBA) && !LOCAL_PMCOLOR_SHIFTS_EQUIVALENT_TO_RGBA
+    #error "SK_PMCOLOR_IS_RGBA does not match SK_*32_SHIFT values"
+#endif
+
+#if defined(SK_PMCOLOR_IS_BGRA) && !LOCAL_PMCOLOR_SHIFTS_EQUIVALENT_TO_BGRA
+    #error "SK_PMCOLOR_IS_BGRA does not match SK_*32_SHIFT values"
+#endif
+
+#if !defined(SK_PMCOLOR_IS_RGBA) && !defined(SK_PMCOLOR_IS_RGBA)
+    // deduce which to define from the _SHIFT defines
+
+    #if LOCAL_PMCOLOR_SHIFTS_EQUIVALENT_TO_RGBA
+        #define SK_PMCOLOR_IS_RGBA
+    #elif LOCAL_PMCOLOR_SHIFTS_EQUIVALENT_TO_BGRA
+        #define SK_PMCOLOR_IS_BGRA
+    #else
+        #error "need 32bit packing to be either RGBA or BGRA"
+    #endif
+#endif
+
+// hide these now that we're done
+#undef LOCAL_PMCOLOR_SHIFTS_EQUIVALENT_TO_RGBA
+#undef LOCAL_PMCOLOR_SHIFTS_EQUIVALENT_TO_BGRA
+
+//////////////////////////////////////////////////////////////////////////////
+
+// Reverse the bytes coorsponding to RED and BLUE in a packed pixels. Note the
+// pair of them are in the same 2 slots in both RGBA and BGRA, thus there is
+// no need to pass in the colortype to this function.
+static inline uint32_t SkSwizzle_RB(uint32_t c) {
+    static const uint32_t kRBMask = (0xFF << SK_R32_SHIFT) | (0xFF << SK_B32_SHIFT);
+
+    unsigned c0 = (c >> SK_R32_SHIFT) & 0xFF;
+    unsigned c1 = (c >> SK_B32_SHIFT) & 0xFF;
+    return (c & ~kRBMask) | (c0 << SK_B32_SHIFT) | (c1 << SK_R32_SHIFT);
+}
+
+static inline uint32_t SkPackARGB_as_RGBA(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
+    SkASSERT_IS_BYTE(a);
+    SkASSERT_IS_BYTE(r);
+    SkASSERT_IS_BYTE(g);
+    SkASSERT_IS_BYTE(b);
+    return (a << SK_RGBA_A32_SHIFT) | (r << SK_RGBA_R32_SHIFT) |
+           (g << SK_RGBA_G32_SHIFT) | (b << SK_RGBA_B32_SHIFT);
+}
+
+static inline uint32_t SkPackARGB_as_BGRA(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
+    SkASSERT_IS_BYTE(a);
+    SkASSERT_IS_BYTE(r);
+    SkASSERT_IS_BYTE(g);
+    SkASSERT_IS_BYTE(b);
+    return (a << SK_BGRA_A32_SHIFT) | (r << SK_BGRA_R32_SHIFT) |
+           (g << SK_BGRA_G32_SHIFT) | (b << SK_BGRA_B32_SHIFT);
+}
+
+static inline SkPMColor SkSwizzle_RGBA_to_PMColor(uint32_t c) {
+#ifdef SK_PMCOLOR_IS_RGBA
+    return c;
+#else
+    return SkSwizzle_RB(c);
+#endif
+}
+
+static inline SkPMColor SkSwizzle_BGRA_to_PMColor(uint32_t c) {
+#ifdef SK_PMCOLOR_IS_BGRA
+    return c;
+#else
+    return SkSwizzle_RB(c);
+#endif
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
 ///@{
 /** See ITU-R Recommendation BT.709 at http://www.itu.int/rec/R-REC-BT.709/ .*/
 #define SK_ITU_BT709_LUM_COEFF_R (0.2126f)
@@ -239,6 +365,16 @@ static inline SkPMColor SkPackARGB32(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
            (g << SK_G32_SHIFT) | (b << SK_B32_SHIFT);
 }
 
+static inline uint32_t SkPackPMColor_as_RGBA(SkPMColor c) {
+    return SkPackARGB_as_RGBA(SkGetPackedA32(c), SkGetPackedR32(c),
+                              SkGetPackedG32(c), SkGetPackedB32(c));
+}
+
+static inline uint32_t SkPackPMColor_as_BGRA(SkPMColor c) {
+    return SkPackARGB_as_BGRA(SkGetPackedA32(c), SkGetPackedR32(c),
+                              SkGetPackedG32(c), SkGetPackedB32(c));
+}
+
 /**
  * Abstract 4-byte interpolation, implemented on top of SkPMColor
  * utility functions. Third parameter controls blending of the first two: