store SkAlphaType inside SkBitmap, on road to support unpremul

src/core/SkBitmap.cpp

 
 /*
  * Copyright 2008 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkBitmap.h"
@@ skipping 248 matching lines @@
                 SkIntToScalar(fWidth), SkIntToScalar(fHeight));
 }
 
 void SkBitmap::getBounds(SkIRect* bounds) const {
     SkASSERT(bounds);
     bounds->set(0, 0, fWidth, fHeight);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
-void SkBitmap::setConfig(Config c, int width, int height, size_t rowBytes) {
-    this->freePixels();
-
+bool SkBitmap::setConfig(Config config, int width, int height, size_t rowBytes,
+                         SkAlphaType alphaType) {
     if ((width | height) < 0) {
-        goto err;
+        goto ERROR;
     }
-
     if (rowBytes == 0) {
-        rowBytes = SkBitmap::ComputeRowBytes(c, width);
-        if (0 == rowBytes && kNo_Config != c) {
-            goto err;
+        rowBytes = SkBitmap::ComputeRowBytes(config, width);
+        if (0 == rowBytes && kNo_Config != config) {
+            goto ERROR;
         }
     }
 
-    fConfig     = SkToU8(c);
+    // check for legal/supported config+alphaType combinations
+    //
+    switch (config) {

[scroggo, 2013/10/18 19:32:40]

Should this call setAlphaType so we don't have code duplication? The comment
"not supported yet" hints that we may be adding that feature in the future, at
which time we'll need to update both pieces of code.

+        case kNo_Config:
+            alphaType = kIgnore_SkAlphaType;    // canonicalize
+            break;
+        case kA1_Config:
+        case kA8_Config:
+            if (kUnpremul_SkAlphaType == alphaType) {
+                alphaType = kPremul_SkAlphaType;
+            }
+            // fall-through
+        case kIndex8_Config:
+        case kARGB_4444_Config:
+        case kARGB_8888_Config:
+            if (kIgnore_SkAlphaType == alphaType) {
+                goto ERROR;   // not supported yet
+            }
+            break;
+        case kRGB_565_Config:
+            alphaType = kOpaque_SkAlphaType;    // canonicalize
+            break;
+    }
+
+    this->freePixels();
+
+    fConfig     = SkToU8(config);
+    fAlphaType  = SkToU8(alphaType);
     fWidth      = width;
     fHeight     = height;
     fRowBytes   = SkToU32(rowBytes);
 
-    fBytesPerPixel = (uint8_t)ComputeBytesPerPixel(c);
+    fBytesPerPixel = (uint8_t)ComputeBytesPerPixel(config);
 
     SkDEBUGCODE(this->validate();)
-    return;
+    return true;
 
     // if we got here, we had an error, so we reset the bitmap to empty
-err:
+ERROR:
     this->reset();
+    return false;
+}
+
+void SkBitmap::setAlphaType(SkAlphaType alphaType) {
+    // check for legal/supported config+alphaType combinations
+    //
+    switch (this->config()) {
+        case kNo_Config:
+            alphaType = kIgnore_SkAlphaType;    // canonicalize
+            break;
+        case kA1_Config:
+        case kA8_Config:
+            if (kUnpremul_SkAlphaType == alphaType) {
+                alphaType = kPremul_SkAlphaType;
+            }
+            // fall-through
+        case kIndex8_Config:
+        case kARGB_4444_Config:
+        case kARGB_8888_Config:
+            if (kIgnore_SkAlphaType == alphaType) {
+                SkDEBUGFAIL("bad alphaType for existing config");
+                return;
+            }
+            break;
+        case kRGB_565_Config:
+            alphaType = kOpaque_SkAlphaType;    // canonicalize
+            break;
+    }
+    
+    fAlphaType = SkToU8(alphaType);
 }
 
 void SkBitmap::updatePixelsFromRef() const {
     if (NULL != fPixelRef) {
         if (fPixelLockCount > 0) {
             SkASSERT(fPixelRef->isLocked());
 
             void* p = fPixelRef->pixels();
             if (NULL != p) {
                 p = (char*)p + fPixelRefOffset;
@@ skipping 212 matching lines @@
 
 void SkBitmap::setImmutable() {
     if (fPixelRef) {
         fPixelRef->setImmutable();
     } else {
         fFlags |= kImageIsImmutable_Flag;
     }
 }
 
 bool SkBitmap::isOpaque() const {
+    return kOpaque_SkAlphaType == fAlphaType ||
+           kIgnore_SkAlphaType == fAlphaType;
+#if 0

[scroggo, 2013/10/18 19:32:40]

Any reason not to delete this code?

     switch (fConfig) {
         case kNo_Config:
             return true;
 
         case kA1_Config:
         case kA8_Config:
         case kARGB_4444_Config:
         case kARGB_8888_Config:
             return (fFlags & kImageIsOpaque_Flag) != 0;
 
         case kIndex8_Config: {
             bool isOpaque;
 
             this->lockPixels();
             isOpaque = fColorTable && fColorTable->isOpaque();
             this->unlockPixels();
             return isOpaque;
         }
 
         case kRGB_565_Config:
             return true;
 
         default:
             SkDEBUGFAIL("unknown bitmap config pased to isOpaque");
             return false;
     }
+#endif
 }
 
+#if 0

[scroggo, 2013/10/18 19:32:40]

Any reason not to delete this code?

 void SkBitmap::setIsOpaque(bool isOpaque) {
     /*  we record this regardless of fConfig, though it is ignored in
         isOpaque() for configs that can't support per-pixel alpha.
     */
     if (isOpaque) {
         fFlags |= kImageIsOpaque_Flag;
     } else {
         fFlags &= ~kImageIsOpaque_Flag;
     }
 }
+#endif
 
 bool SkBitmap::isVolatile() const {
     return (fFlags & kImageIsVolatile_Flag) != 0;
 }
 
 void SkBitmap::setIsVolatile(bool isVolatile) {
     if (isVolatile) {
         fFlags |= kImageIsVolatile_Flag;
     } else {
         fFlags &= ~kImageIsVolatile_Flag;
@@ skipping 375 matching lines @@
     srcRect.set(0, 0, this->width(), this->height());
     if (!r.intersect(srcRect, subset)) {
         return false;   // r is empty (i.e. no intersection)
     }
 
     if (fPixelRef->getTexture() != NULL) {
         // Do a deep copy
         SkPixelRef* pixelRef = fPixelRef->deepCopy(this->config(), &subset);
         if (pixelRef != NULL) {
             SkBitmap dst;
-            dst.setConfig(this->config(), subset.width(), subset.height());
+            dst.setConfig(this->config(), subset.width(), subset.height(), 0,
+                          this->isOpaque() ?

[scroggo, 2013/10/18 19:32:40]

Why not use fAlphaType?

+                          kOpaque_SkAlphaType : kPremul_SkAlphaType);
             dst.setIsVolatile(this->isVolatile());
-            dst.setIsOpaque(this->isOpaque());
             dst.setPixelRef(pixelRef)->unref();
             SkDEBUGCODE(dst.validate());
             result->swap(dst);
             return true;
         }
     }
 
     // If the upper left of the rectangle was outside the bounds of this SkBitmap, we should have
     // exited above.
     SkASSERT(static_cast<unsigned>(r.fLeft) < static_cast<unsigned>(this->width()));
     SkASSERT(static_cast<unsigned>(r.fTop) < static_cast<unsigned>(this->height()));
 
     size_t offset = get_sub_offset(*this, r.fLeft, r.fTop);
     if (SUB_OFFSET_FAILURE == offset) {
         return false;   // config not supported
     }
 
     SkBitmap dst;
-    dst.setConfig(this->config(), r.width(), r.height(), this->rowBytes());
+    dst.setConfig(this->config(), r.width(), r.height(), this->rowBytes(),
+                  this->isOpaque() ? kOpaque_SkAlphaType : kPremul_SkAlphaType);

[scroggo, 2013/10/18 19:32:40]

fAlphaType?

     dst.setIsVolatile(this->isVolatile());
-    dst.setIsOpaque(this->isOpaque());
 
     if (fPixelRef) {
         // share the pixelref with a custom offset
         dst.setPixelRef(fPixelRef, fPixelRefOffset + offset);
     }
     SkDEBUGCODE(dst.validate();)
 
     // we know we're good, so commit to result
     result->swap(dst);
     return true;
@@ skipping 128 matching lines @@
         // TODO: switch the allocation of tmpDst to call sk_calloc_throw
         tmpDst.eraseColor(SK_ColorTRANSPARENT);
 
         SkCanvas canvas(tmpDst);
         SkPaint  paint;
 
         paint.setDither(true);
         canvas.drawBitmap(*src, 0, 0, &paint);
     }
 
-    tmpDst.setIsOpaque(src->isOpaque());
+    tmpDst.setAlphaType(src->isOpaque() ?

[scroggo, 2013/10/18 19:32:40]

It seems odd here to set the alpha type after we've drawn to it. It might need
to be specified individually for the different cases. If we did a straight
memcpy (i.e. if the configs are the same), we should be setting it to
fAlphaType. If we are copying from 8888 to 565, it is odd to potentially set it
to Premul (though setAlphaType will correct that for us). If we're doing some
other copy (8888 to 4444, if we'll still allow that), we'd want the dest to be
unpremul if the source was (assuming we copied it as unpremul).

+                        kOpaque_SkAlphaType : kPremul_SkAlphaType);
 
     dst->swap(tmpDst);
     return true;
 }
 
 bool SkBitmap::deepCopyTo(SkBitmap* dst, Config dstConfig) const {
     if (!this->canCopyTo(dstConfig)) {
         return false;
     }
 
@@ skipping 452 matching lines @@
 }
 
 void SkBitmap::unflatten(SkFlattenableReadBuffer& buffer) {
     this->reset();
 
     int width = buffer.readInt();
     int height = buffer.readInt();
     int rowBytes = buffer.readInt();
     int config = buffer.readInt();
 
-    this->setConfig((Config)config, width, height, rowBytes);
-    this->setIsOpaque(buffer.readBool());
+    bool isOpaque = buffer.readBool();

[scroggo, 2013/10/18 19:32:40]

Why not update flatten to write the alpha type and then set it directly here?

+    this->setConfig((Config)config, width, height, rowBytes,
+                    isOpaque ? kOpaque_SkAlphaType : kPremul_SkAlphaType);
 
     int reftype = buffer.readInt();
     switch (reftype) {
         case SERIALIZE_PIXELTYPE_REF_DATA: {
             size_t offset = buffer.readUInt();
             SkPixelRef* pr = buffer.readPixelRef();
             SkSafeUnref(this->setPixelRef(pr, offset));
             break;
         }
         case SERIALIZE_PIXELTYPE_NONE:
@@ skipping 75 matching lines @@
         if (NULL != uri) {
             str->appendf(" uri:\"%s\"", uri);
         } else {
             str->appendf(" pixelref:%p", pr);
         }
     }
 
     str->append(")");
 }
 #endif