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* 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.
#ifndef SkPixelRef_DEFINED
#define SkPixelRef_DEFINED
#include "SkBitmap.h"
#include "SkRefCnt.h"
#include "SkString.h"
#include "SkFlattenable.h"
#include "SkImageInfo.h"
#include "SkTDArray.h"
//#define xed
#ifdef SK_DEBUG
* Defining SK_IGNORE_PIXELREF_SETPRELOCKED will force all pixelref
* subclasses to correctly handle lock/unlock pixels. For performance
* reasons, simple malloc-based subclasses call setPreLocked() to skip
* the overhead of implementing these calls.
* This build-flag disables that optimization, to add in debugging our
* call-sites, to ensure that they correctly balance their calls of
* lock and unlock.
class SkColorTable;
class SkData;
struct SkIRect;
class SkMutex;
class GrTexture;
/** \class SkPixelRef
This class is the smart container for pixel memory, and is used with
SkBitmap. A pixelref is installed into a bitmap, and then the bitmap can
access the actual pixel memory by calling lockPixels/unlockPixels.
This class can be shared/accessed between multiple threads.
class SK_API SkPixelRef : public SkFlattenable {
explicit SkPixelRef(const SkImageInfo&);
SkPixelRef(const SkImageInfo&, SkBaseMutex* mutex);
virtual ~SkPixelRef();
const SkImageInfo& info() const {
return fInfo;
/** Return the pixel memory returned from lockPixels, or null if the
lockCount is 0.
void* pixels() const { return fRec.fPixels; }
/** Return the current colorTable (if any) if pixels are locked, or null.
SkColorTable* colorTable() const { return fRec.fColorTable; }
size_t rowBytes() const { return fRec.fRowBytes; }
* To access the actual pixels of a pixelref, it must be "locked".
* Calling lockPixels returns a LockRec struct (on success).
struct LockRec {
void* fPixels;
SkColorTable* fColorTable;
size_t fRowBytes;
void zero() { sk_bzero(this, sizeof(*this)); }
bool isZero() const {
return NULL == fPixels && NULL == fColorTable && 0 == fRowBytes;
* Returns true if the lockcount > 0
bool isLocked() const { return fLockCount > 0; }
SkDEBUGCODE(int getLockCount() const { return fLockCount; })
* Call to access the pixel memory. Return true on success. Balance this
* with a call to unlockPixels().
bool lockPixels();
* Call to access the pixel memory. On success, return true and fill out
* the specified rec. On failure, return false and ignore the rec parameter.
* Balance this with a call to unlockPixels().
bool lockPixels(LockRec* rec);
/** Call to balanace a previous call to lockPixels(). Returns the pixels
(or null) after the unlock. NOTE: lock calls can be nested, but the
matching number of unlock calls must be made in order to free the
memory (if the subclass implements caching/deferred-decoding.)
void unlockPixels();
* Some bitmaps can return a copy of their pixels for lockPixels(), but
* that copy, if modified, will not be pushed back. These bitmaps should
* not be used as targets for a raster device/canvas (since all pixels
* modifications will be lost when unlockPixels() is called.)
bool lockPixelsAreWritable() const;
/** Returns a non-zero, unique value corresponding to the pixels in this
pixelref. Each time the pixels are changed (and notifyPixelsChanged is
called), a different generation ID will be returned.
uint32_t getGenerationID() const;
* Call this if you have changed the contents of the pixels. This will in-
* turn cause a different generation ID value to be returned from
* getGenerationID().
void notifyPixelsChanged();
* Change the info's AlphaType. Note that this does not automatically
* invalidate the generation ID. If the pixel values themselves have
* changed, then you must explicitly call notifyPixelsChanged() as well.
void changeAlphaType(SkAlphaType at);
/** Returns true if this pixelref is marked as immutable, meaning that the
contents of its pixels will not change for the lifetime of the pixelref.
bool isImmutable() const { return fIsImmutable; }
/** Marks this pixelref is immutable, meaning that the contents of its
pixels will not change for the lifetime of the pixelref. This state can
be set on a pixelref, but it cannot be cleared once it is set.
void setImmutable();
/** Return the optional URI string associated with this pixelref. May be
const char* getURI() const { return fURI.size() ? fURI.c_str() : NULL; }
/** Copy a URI string to this pixelref, or clear the URI if the uri is null
void setURI(const char uri[]) {
/** Copy a URI string to this pixelref
void setURI(const char uri[], size_t len) {
fURI.set(uri, len);
/** Assign a URI string to this pixelref.
void setURI(const SkString& uri) { fURI = uri; }
* If the pixelRef has an encoded (i.e. compressed) representation,
* return a ref to its data. If the pixelRef
* is uncompressed or otherwise does not have this form, return NULL.
* If non-null is returned, the caller is responsible for calling unref()
* on the data when it is finished.
SkData* refEncodedData() {
return this->onRefEncodedData();
* Experimental -- tells the caller if it is worth it to call decodeInto().
* Just an optimization at this point, to avoid checking the cache first.
* We may remove/change this call in the future.
bool implementsDecodeInto() {
return this->onImplementsDecodeInto();
* Return a decoded instance of this pixelRef in bitmap. If this cannot be
* done, return false and the bitmap parameter is ignored/unchanged.
* pow2 is the requeste power-of-two downscale that the caller needs. This
* can be ignored, and the "original" size can be returned, but if the
* underlying codec can efficiently return a smaller size, that should be
* done. Some examples:
* To request the "base" version (original scale), pass 0 for pow2
* To request 1/2 scale version (1/2 width, 1/2 height), pass 1 for pow2
* To request 1/4 scale version (1/4 width, 1/4 height), pass 2 for pow2
* ...
* If this returns true, then bitmap must be "locked" such that
* bitmap->getPixels() will return the correct address.
bool decodeInto(int pow2, SkBitmap* bitmap) {
SkASSERT(pow2 >= 0);
return this->onDecodeInto(pow2, bitmap);
/** Are we really wrapping a texture instead of a bitmap?
virtual GrTexture* getTexture() { return NULL; }
bool readPixels(SkBitmap* dst, const SkIRect* subset = NULL);
* Makes a deep copy of this PixelRef, respecting the requested config.
* @param colorType Desired colortype.
* @param subset Subset of this PixelRef to copy. Must be fully contained within the bounds of
* of this PixelRef.
* @return A new SkPixelRef, or NULL if either there is an error (e.g. the destination could
* not be created with the given config), or this PixelRef does not support deep
* copies.
virtual SkPixelRef* deepCopy(SkColorType colortype, const SkIRect* subset) {
return NULL;
* Acquire a "global" ref on this object.
* The default implementation just calls ref(), but subclasses can override
* this method to implement additional behavior.
virtual void globalRef(void* data=NULL);
* Release a "global" ref on this object.
* The default implementation just calls unref(), but subclasses can override
* this method to implement additional behavior.
virtual void globalUnref();
// Register a listener that may be called the next time our generation ID changes.
// We'll only call the listener if we're confident that we are the only SkPixelRef with this
// generation ID. If our generation ID changes and we decide not to call the listener, we'll
// never call it: you must add a new listener for each generation ID change. We also won't call
// the listener when we're certain no one knows what our generation ID is.
// This can be used to invalidate caches keyed by SkPixelRef generation ID.
struct GenIDChangeListener {
virtual ~GenIDChangeListener() {}
virtual void onChange() = 0;
// Takes ownership of listener.
void addGenIDChangeListener(GenIDChangeListener* listener);
* On success, returns true and fills out the LockRec for the pixels. On
* failure returns false and ignores the LockRec parameter.
* The caller will have already acquired a mutex for thread safety, so this
* method need not do that.
virtual bool onNewLockPixels(LockRec*) = 0;
* Balancing the previous successful call to onNewLockPixels. The locked
* pixel address will no longer be referenced, so the subclass is free to
* move or discard that memory.
* The caller will have already acquired a mutex for thread safety, so this
* method need not do that.
virtual void onUnlockPixels() = 0;
/** Default impl returns true */
virtual bool onLockPixelsAreWritable() const;
// returns false;
virtual bool onImplementsDecodeInto();
// returns false;
virtual bool onDecodeInto(int pow2, SkBitmap* bitmap);
* For pixelrefs that don't have access to their raw pixels, they may be
* able to make a copy of them (e.g. if the pixels are on the GPU).
* The base class implementation returns false;
virtual bool onReadPixels(SkBitmap* dst, const SkIRect* subsetOrNull);
// default impl returns NULL.
virtual SkData* onRefEncodedData();
* Returns the size (in bytes) of the internally allocated memory.
* This should be implemented in all serializable SkPixelRef derived classes.
* SkBitmap::fPixelRefOffset + SkBitmap::getSafeSize() should never overflow this value,
* otherwise the rendering code may attempt to read memory out of bounds.
* @return default impl returns 0.
virtual size_t getAllocatedSizeInBytes() const;
/** Return the mutex associated with this pixelref. This value is assigned
in the constructor, and cannot change during the lifetime of the object.
SkBaseMutex* mutex() const { return fMutex; }
// serialization
SkPixelRef(SkReadBuffer&, SkBaseMutex*);
virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
// only call from constructor. Flags this to always be locked, removing
// the need to grab the mutex and call onLockPixels/onUnlockPixels.
// Performance tweak to avoid those calls (esp. in multi-thread use case).
void setPreLocked(void*, size_t rowBytes, SkColorTable*);
SkBaseMutex* fMutex; // must remain in scope for the life of this object
// mostly const. fInfo.fAlpahType can be changed at runtime.
const SkImageInfo fInfo;
// LockRec is only valid if we're in a locked state (isLocked())
LockRec fRec;
int fLockCount;
mutable uint32_t fGenerationID;
mutable bool fUniqueGenerationID;
SkTDArray<GenIDChangeListener*> fGenIDChangeListeners; // pointers are owned
SkString fURI;
// can go from false to true, but never from true to false
bool fIsImmutable;
// only ever set in constructor, const after that
bool fPreLocked;
void needsNewGenID();
void callGenIDChangeListeners();
void setMutex(SkBaseMutex* mutex);
// When copying a bitmap to another with the same shape and config, we can safely
// clone the pixelref generation ID too, which makes them equivalent under caching.
friend class SkBitmap; // only for cloneGenID
void cloneGenID(const SkPixelRef&);
typedef SkFlattenable INHERITED;
class SkPixelRefFactory : public SkRefCnt {
* Allocate a new pixelref matching the specified ImageInfo, allocating
* the memory for the pixels. If the ImageInfo requires a ColorTable,
* the pixelref will ref() the colortable.
* On failure return NULL.
virtual SkPixelRef* create(const SkImageInfo&, SkColorTable*) = 0;