Adjust the alpha type for pixelRefs.

Move SkBitmap's validate_alphaType to SkImageInfo, with the new
name SkColorTypeValidateAlphaType. Use it in SkPixelRef's constructors,
as well as in SkDecodingImageGenerator. This fixes a bug where an
SkPixelRef's SkAlphaType could get out of sync with its SkBitmap,
when both were assigned the same SkAlphaType.

R=reed@google.com, halcanary@google.com

Author: scroggo@google.com

Review URL: https://codereview.chromium.org/346593003

4 files changed, 50 insertions, 35 deletions

diff --git a/src/core/SkBitmap.cpp b/src/core/SkBitmap.cpp
index 38df07c75f..82e0b4c92b 100644
--- a/src/core/SkBitmap.cpp
+++ b/src/core/SkBitmap.cpp
@@ -152,42 +152,11 @@ void SkBitmap::getBounds(SkIRect* bounds) const {
 
 ///////////////////////////////////////////////////////////////////////////////
 
-static bool validate_alphaType(SkColorType colorType, SkAlphaType alphaType,
-                               SkAlphaType* canonical = NULL) {
-    switch (colorType) {
-        case kUnknown_SkColorType:
-            alphaType = kIgnore_SkAlphaType;
-            break;
-        case kAlpha_8_SkColorType:
-            if (kUnpremul_SkAlphaType == alphaType) {
-                alphaType = kPremul_SkAlphaType;
-            }
-            // fall-through
-        case kIndex_8_SkColorType:
-        case kARGB_4444_SkColorType:
-        case kRGBA_8888_SkColorType:
-        case kBGRA_8888_SkColorType:
-            if (kIgnore_SkAlphaType == alphaType) {
-                return false;
-            }
-            break;
-        case kRGB_565_SkColorType:
-            alphaType = kOpaque_SkAlphaType;
-            break;
-        default:
-            return false;
-    }
-    if (canonical) {
-        *canonical = alphaType;
-    }
-    return true;
-}
-
 bool SkBitmap::setInfo(const SkImageInfo& origInfo, size_t rowBytes) {
     SkImageInfo info = origInfo;
 
-    if (!validate_alphaType(info.fColorType, info.fAlphaType,
-                            &info.fAlphaType)) {
+    if (!SkColorTypeValidateAlphaType(info.fColorType, info.fAlphaType,
+                                      &info.fAlphaType)) {
         return reset_return_false(this);
     }
 
@@ -228,7 +197,7 @@ bool SkBitmap::setConfig(Config config, int width, int height, size_t rowBytes,
 #endif
 
 bool SkBitmap::setAlphaType(SkAlphaType alphaType) {
-    if (!validate_alphaType(fInfo.fColorType, alphaType, &alphaType)) {
+    if (!SkColorTypeValidateAlphaType(fInfo.fColorType, alphaType, &alphaType)) {
         return false;
     }
     if (fInfo.fAlphaType != alphaType) {
@@ -1332,7 +1301,7 @@ void SkBitmap::legacyUnflatten(SkReadBuffer& buffer) {
     if (!buffer.validate((info.width() >= 0) && (info.height() >= 0) &&
                          SkColorTypeIsValid(info.fColorType) &&
                          SkAlphaTypeIsValid(info.fAlphaType) &&
-                         validate_alphaType(info.fColorType, info.fAlphaType) &&
+                         SkColorTypeValidateAlphaType(info.fColorType, info.fAlphaType) &&
                          info.validRowBytes(rowBytes))) {
         return;
     }
diff --git a/src/core/SkImageInfo.cpp b/src/core/SkImageInfo.cpp
index 27c457391f..e61cd7d45f 100644
--- a/src/core/SkImageInfo.cpp
+++ b/src/core/SkImageInfo.cpp
@@ -38,3 +38,34 @@ void SkImageInfo::flatten(SkWriteBuffer& buffer) const {
     uint32_t packed = (fAlphaType << 8) | fColorType;
     buffer.write32(packed);
 }
+
+bool SkColorTypeValidateAlphaType(SkColorType colorType, SkAlphaType alphaType,
+                                  SkAlphaType* canonical) {
+    switch (colorType) {
+        case kUnknown_SkColorType:
+            alphaType = kIgnore_SkAlphaType;
+            break;
+        case kAlpha_8_SkColorType:
+            if (kUnpremul_SkAlphaType == alphaType) {
+                alphaType = kPremul_SkAlphaType;
+            }
+            // fall-through
+        case kIndex_8_SkColorType:
+        case kARGB_4444_SkColorType:
+        case kRGBA_8888_SkColorType:
+        case kBGRA_8888_SkColorType:
+            if (kIgnore_SkAlphaType == alphaType) {
+                return false;
+            }
+            break;
+        case kRGB_565_SkColorType:
+            alphaType = kOpaque_SkAlphaType;
+            break;
+        default:
+            return false;
+    }
+    if (canonical) {
+        *canonical = alphaType;
+    }
+    return true;
+}
diff --git a/src/core/SkPixelRef.cpp b/src/core/SkPixelRef.cpp
index bfa4ae24d9..829c3f1b12 100644
--- a/src/core/SkPixelRef.cpp
+++ b/src/core/SkPixelRef.cpp
@@ -84,6 +84,9 @@ void SkPixelRef::setMutex(SkBaseMutex* mutex) {
 #define SKPIXELREF_PRELOCKED_LOCKCOUNT     123456789
 
 SkPixelRef::SkPixelRef(const SkImageInfo& info) : fInfo(info) {
+    SkAssertResult(SkColorTypeValidateAlphaType(fInfo.colorType(), fInfo.alphaType(),
+                                                const_cast<SkAlphaType*>(&fInfo.fAlphaType)));
+
     this->setMutex(NULL);
     fRec.zero();
     fLockCount = 0;
@@ -94,6 +97,9 @@ SkPixelRef::SkPixelRef(const SkImageInfo& info) : fInfo(info) {
 
 
 SkPixelRef::SkPixelRef(const SkImageInfo& info, SkBaseMutex* mutex) : fInfo(info) {
+    SkAssertResult(SkColorTypeValidateAlphaType(fInfo.colorType(), fInfo.alphaType(),
+                                                const_cast<SkAlphaType*>(&fInfo.fAlphaType)));
+
     this->setMutex(mutex);
     fRec.zero();
     fLockCount = 0;
@@ -112,6 +118,10 @@ SkPixelRef::SkPixelRef(SkReadBuffer& buffer, SkBaseMutex* mutex)
         : INHERITED(buffer)
         , fInfo(read_info(buffer))
 {
+    SkDEBUGCODE(SkAlphaType alphaType;)
+    SkASSERT(SkColorTypeValidateAlphaType(fInfo.colorType(), fInfo.alphaType(), &alphaType));
+    SkASSERT(fInfo.fAlphaType == alphaType);
+
     this->setMutex(mutex);
     fRec.zero();
     fLockCount = 0;
diff --git a/src/images/SkDecodingImageGenerator.cpp b/src/images/SkDecodingImageGenerator.cpp
index 88cdef9a32..dfa093becc 100644
--- a/src/images/SkDecodingImageGenerator.cpp
+++ b/src/images/SkDecodingImageGenerator.cpp
@@ -246,6 +246,11 @@ SkImageGenerator* CreateDecodingImageGenerator(
     if (opts.fRequireUnpremul && info.fAlphaType != kOpaque_SkAlphaType) {
         info.fAlphaType = kUnpremul_SkAlphaType;
     }
+
+    if (!SkColorTypeValidateAlphaType(info.fColorType, info.fAlphaType, &info.fAlphaType)) {
+        return NULL;
+    }
+
     return SkNEW_ARGS(DecodingImageGenerator,
                       (data, autoStream.detach(), info,
                        opts.fSampleSize, opts.fDitherImage));