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* Copyright 2013 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SkImageGenerator_DEFINED
#define SkImageGenerator_DEFINED
#include "SkBitmap.h"
#include "SkColor.h"
#include "SkImage.h"
#include "SkImageInfo.h"
#include "SkYUVSizeInfo.h"
class GrContext;
class GrContextThreadSafeProxy;
class GrTexture;
class GrSamplerParams;
class SkBitmap;
class SkData;
class SkMatrix;
class SkPaint;
class SkPicture;
class SK_API SkImageGenerator : public SkNoncopyable {
* The PixelRef which takes ownership of this SkImageGenerator
* will call the image generator's destructor.
virtual ~SkImageGenerator() { }
uint32_t uniqueID() const { return fUniqueID; }
* Return a ref to the encoded (i.e. compressed) representation,
* of this data. If the GrContext is non-null, then the caller is only interested in
* gpu-specific formats, so the impl may return null even if they have encoded data,
* assuming they know it is not suitable for the gpu.
* If non-NULL is returned, the caller is responsible for calling
* unref() on the data when it is finished.
SkData* refEncodedData(GrContext* ctx = nullptr) {
return this->onRefEncodedData(ctx);
* Return the ImageInfo associated with this generator.
const SkImageInfo& getInfo() const { return fInfo; }
* Decode into the given pixels, a block of memory of size at
* least (info.fHeight - 1) * rowBytes + (info.fWidth *
* bytesPerPixel)
* Repeated calls to this function should give the same results,
* allowing the PixelRef to be immutable.
* @param info A description of the format (config, size)
* expected by the caller. This can simply be identical
* to the info returned by getInfo().
* This contract also allows the caller to specify
* different output-configs, which the implementation can
* decide to support or not.
* A size that does not match getInfo() implies a request
* to scale. If the generator cannot perform this scale,
* it will return kInvalidScale.
* If info is kIndex8_SkColorType, then the caller must provide storage for up to 256
* SkPMColor values in ctable. On success the generator must copy N colors into that storage,
* (where N is the logical number of table entries) and set ctableCount to N.
* If info is not kIndex8_SkColorType, then the last two parameters may be NULL. If ctableCount
* is not null, it will be set to 0.
* @return true on success.
bool getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
SkPMColor ctable[], int* ctableCount);
* Simplified version of getPixels() that asserts that info is NOT kIndex8_SkColorType and
* uses the default Options.
bool getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes);
* If decoding to YUV is supported, this returns true. Otherwise, this
* returns false and does not modify any of the parameters.
* @param sizeInfo Output parameter indicating the sizes and required
* allocation widths of the Y, U, and V planes.
* @param colorSpace Output parameter.
bool queryYUV8(SkYUVSizeInfo* sizeInfo, SkYUVColorSpace* colorSpace) const;
* Returns true on success and false on failure.
* This always attempts to perform a full decode. If the client only
* wants size, it should call queryYUV8().
* @param sizeInfo Needs to exactly match the values returned by the
* query, except the WidthBytes may be larger than the
* recommendation (but not smaller).
* @param planes Memory for each of the Y, U, and V planes.
bool getYUV8Planes(const SkYUVSizeInfo& sizeInfo, void* planes[3]);
* If the generator can natively/efficiently return its pixels as a GPU image (backed by a
* texture) this will return that image. If not, this will return NULL.
* This routine also supports retrieving only a subset of the pixels. That subset is specified
* by the following rectangle:
* subset = SkIRect::MakeXYWH(origin.x(), origin.y(), info.width(), info.height())
* If subset is not contained inside the generator's bounds, this returns false.
* whole = SkIRect::MakeWH(getInfo().width(), getInfo().height())
* if (!whole.contains(subset)) {
* return false;
* }
* Regarding the GrContext parameter:
* The caller may pass NULL for the context. In that case the generator may assume that its
* internal context is current. If it has no internal context, then it should just return
* null.
* If the caller passes a non-null context, then the generator should only succeed if:
* - it has no intrinsic context, and will use the caller's
* - its internal context is the same
* - it can somehow convert its texture into one that is valid for the provided context.
GrTexture* generateTexture(GrContext*, const SkImageInfo& info, const SkIPoint& origin);
struct SupportedSizes {
SkISize fSizes[2];
* Some generators can efficiently scale their contents. If this is supported, the generator
* may only support certain scaled dimensions. Call this with the desired scale factor,
* and it will return true if scaling is supported, and in supportedSizes[] it will return
* the nearest supported dimensions.
* If no native scaling is supported, or scale is invalid (e.g. scale <= 0 || scale > 1)
* this will return false, and the supportedsizes will be undefined.
bool computeScaledDimensions(SkScalar scale, SupportedSizes*);
* Copy the pixels from this generator into the provided pixmap, respecting
* all of the pixmap's attributes: dimensions, colortype, alphatype, colorspace.
* returns true on success.
* Some generators can only scale to certain dimensions (e.g. powers-of-2 smaller).
* Thus a generator may fail (return false) for some sizes but succeed for other sizes.
* Call computeScaledDimensions() to know, for a given requested scale, what output size(s)
* the generator might support.
* Note: this call does NOT allocate the memory for the pixmap; that must be done
* by the caller.
bool generateScaledPixels(const SkPixmap& scaledPixels);
* External generator API: provides efficient access to externally-managed image data.
* Skia calls accessScaledPixels() during rasterization, to gain temporary access to
* the external pixel data. When done, the provided callback is invoked to release the
* associated resources.
* @param srcRect the source rect in use for the current draw
* @param totalMatrix full matrix in effect (mapping srcRect -> device space)
* @param quality the SkFilterQuality requested for rasterization.
* @param rec out param, expected to be set when the call succeeds:
* - fPixmap external pixel data
* - fSrcRect is an adjusted srcRect
* - fQuality is the adjusted filter quality
* - fReleaseProc pixmap release callback, same signature as the
* SkBitmap::installPixels() callback
* - fReleaseCtx opaque release context argument
* @return true on success, false otherwise (error or if this API is not supported;
* in this case Skia will fall back to its internal scaling and caching
* heuristics)
* Implementors can return pixmaps with a different size than requested, by adjusting the
* src rect. The contract is that Skia will observe the adjusted src rect, and will map it
* to the same dest as the original draw (the impl doesn't get to control the destination).
struct ScaledImageRec {
SkPixmap fPixmap;
SkRect fSrcRect;
SkFilterQuality fQuality;
using ReleaseProcT = void (*)(void* pixels, void* releaseCtx);
ReleaseProcT fReleaseProc;
void* fReleaseCtx;
bool accessScaledImage(const SkRect& srcRect, const SkMatrix& totalMatrix,
SkFilterQuality quality, ScaledImageRec* rec);
* If the default image decoder system can interpret the specified (encoded) data, then
* this returns a new ImageGenerator for it. Otherwise this returns NULL. Either way
* the caller is still responsible for managing their ownership of the data.
static SkImageGenerator* NewFromEncoded(SkData*);
/** Return a new image generator backed by the specified picture. If the size is empty or
* the picture is NULL, this returns NULL.
* The optional matrix and paint arguments are passed to drawPicture() at rasterization
* time.
static SkImageGenerator* NewFromPicture(const SkISize&, const SkPicture*, const SkMatrix*,
const SkPaint*, SkImage::BitDepth, sk_sp<SkColorSpace>);
bool tryGenerateBitmap(SkBitmap* bm, const SkImageInfo& info, SkBitmap::Allocator* allocator);
enum {
kNeedNewImageUniqueID = 0
SkImageGenerator(const SkImageInfo& info, uint32_t uniqueId = kNeedNewImageUniqueID);
virtual SkData* onRefEncodedData(GrContext* ctx);
virtual bool onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
SkPMColor ctable[], int* ctableCount);
virtual bool onQueryYUV8(SkYUVSizeInfo*, SkYUVColorSpace*) const {
return false;
virtual bool onGetYUV8Planes(const SkYUVSizeInfo&, void*[3] /*planes*/) {
return false;
virtual GrTexture* onGenerateTexture(GrContext*, const SkImageInfo&, const SkIPoint&) {
return nullptr;
virtual bool onComputeScaledDimensions(SkScalar, SupportedSizes*) {
return false;
virtual bool onGenerateScaledPixels(const SkPixmap&) {
return false;
virtual bool onAccessScaledImage(const SkRect&, const SkMatrix&, SkFilterQuality,
ScaledImageRec*) {
return false;
const SkImageInfo fInfo;
const uint32_t fUniqueID;
// This is our default impl, which may be different on different platforms.
// It is called from NewFromEncoded() after it has checked for any runtime factory.
// The SkData will never be NULL, as that will have been checked by NewFromEncoded.
static SkImageGenerator* NewFromEncodedImpl(SkData*);
#endif // SkImageGenerator_DEFINED