SkSurface Reference

Surface

Class SkSurface

SkSurface is responsible for managing the pixels that a canvas draws into. The pixels can be allocated either in CPU memory (a raster surface) or on the GPU (a GrRenderTarget surface). SkSurface takes care of allocating a SkCanvas that will draw into the surface. Call surface->getCanvas to use that canvas (but don’t delete it, it is owned by the surface). SkSurface always has non-zero dimensions. If there is a request for a new surface, and either of the requested dimensions are zero, then nullptr will be returned.

Overview

Subtopics

topics description

Member Functions

description function
MakeFromBackendRenderTarget Creates Surface from GPU memory buffer.
MakeFromBackendTexture Creates Surface from GPU-backed texture.
MakeFromBackendTextureAsRenderTarget Creates Surface from GPU-backed texture.
MakeNull Creates Surface without backing pixels.
MakeRaster Creates Surface from SkImageInfo.
MakeRasterDirect Creates Surface from SkImageInfo and Pixel Storage.
MakeRasterDirectReleaseProc Creates Surface from SkImageInfo and Pixel Storage.
MakeRasterN32Premul Creates Surface from width, height matching output.
MakeRenderTarget Creates Surface pointing to new GPU memory buffer.
characterize Set up Surface Characterization for threaded pre-processing.
draw Draws Surface contents to canvas.
flush Resolve pending I/O.
flushAndSignalSemaphores Resolve pending I/O, and signal.
generationID Returns unique ID.
getCanvas Returns Canvas that draws into Surface.
getRenderTargetHandle Returns the GPU reference to render target.
getTextureHandle Returns the GPU reference to texture.
height Returns pixel row count.
makeImageSnapshot Returns Image capturing Surface contents.
makeSurface Returns a compatible Surface.
notifyContentWillChange Notifies that contents will be changed outside of Skia.
peekPixels Copies Surface parameters to Pixmap.
prepareForExternalIO To be deprecated.
props Returns Surface Properties.
readPixels Copies Rect of pixels.
wait Pause commands until signaled.
width Returns pixel column count.

MakeRasterDirect

static sk_sp<SkSurface> MakeRasterDirect(const SkImageInfo& imageInfo, void* pixels, size_t rowBytes,
                                         const SkSurfaceProps* surfaceProps = nullptr)

Allocates raster Surface. Canvas returned by Surface draws directly into pixels.

Surface is returned if all parameters are valid. Valid parameters include: info dimensions are greater than zero; info contains Image Color Type and Image Alpha Type supported by Raster Surface; pixels is not nullptr; rowBytes is large enough to contain info width pixels of Image Color Type.

Pixel buffer size should be info height times computed rowBytes. Pixels are not initialized. To access pixels after drawing, call flush or peekPixels.

Parameters

imageInfo width, height, Image Color Type, Image Alpha Type, Color Space, of Raster Surface; width and height must be greater than zero
pixels pointer to destination pixels buffer
rowBytes interval from one Surface row to the next
surfaceProps LCD striping orientation and setting for device independent fonts; may be nullptr

Return Value

Surface if all parameters are valid; otherwise, nullptr

Example

#### Example Output ~~~~ --- -x- --- ~~~~

See Also

MakeRasterDirectReleaseProc MakeRaster MakeRasterN32Premul SkCanvas::MakeRasterDirect


MakeRasterDirectReleaseProc

static sk_sp<SkSurface> MakeRasterDirectReleaseProc(const SkImageInfo& imageInfo, void* pixels,
                                           size_t rowBytes, void (*releaseProc) (void* pixels,
                                           void* context) , void* context,
                                           const SkSurfaceProps* surfaceProps = nullptr)

Allocates raster Surface. Canvas returned by Surface draws directly into pixels. releaseProc is called with pixels and context when Surface is deleted.

Surface is returned if all parameters are valid. Valid parameters include: info dimensions are greater than zero; info contains Image Color Type and Image Alpha Type supported by Raster Surface; pixels is not nullptr; rowBytes is large enough to contain info width pixels of Image Color Type.

Pixel buffer size should be info height times computed rowBytes. Pixels are not initialized. To access pixels after drawing, call flush or peekPixels.

Parameters

imageInfo width, height, Image Color Type, Image Alpha Type, Color Space, of Raster Surface; width and height must be greater than zero
pixels pointer to destination pixels buffer
rowBytes interval from one Surface row to the next
releaseProc called when Surface is deleted; may be nullptr
context passed to releaseProc; may be nullptr
surfaceProps LCD striping orientation and setting for device independent fonts; may be nullptr

Return Value

Surface if all parameters are valid; otherwise, nullptr

Example

#### Example Output ~~~~ --- -x- --- expected release context ~~~~

See Also

MakeRasterDirect MakeRasterN32Premul MakeRaster


MakeRaster

static sk_sp<SkSurface> MakeRaster(const SkImageInfo& imageInfo, size_t rowBytes,
                                   const SkSurfaceProps* surfaceProps)

Allocates raster Surface. Canvas returned by Surface draws directly into pixels. Allocates and zeroes pixel memory. Pixel memory size is imageInfo.height times rowBytes, or times imageInfo.minRowBytes() if rowBytes is zero. Pixel memory is deleted when Surface is deleted.

Surface is returned if all parameters are valid. Valid parameters include: info dimensions are greater than zero; info contains Image Color Type and Image Alpha Type supported by Raster Surface; rowBytes is large enough to contain info width pixels of Image Color Type, or is zero.

If rowBytes is not zero, subsequent images returned by makeImageSnapshot have the same rowBytes.

Parameters

imageInfo width, height, Image Color Type, Image Alpha Type, Color Space, of Raster Surface; width and height must be greater than zero
rowBytes interval from one Surface row to the next; may be zero
surfaceProps LCD striping orientation and setting for device independent fonts; may be nullptr

Return Value

Surface if all parameters are valid; otherwise, nullptr

Example

#### Example Output ~~~~ --- -x- --- ~~~~

See Also

MakeRasterDirect MakeRasterN32Premul MakeRasterDirectReleaseProc


static sk_sp<SkSurface> MakeRaster(const SkImageInfo& imageInfo,
                                   const SkSurfaceProps* props = nullptr)

Allocates raster Surface. Canvas returned by Surface draws directly into pixels. Allocates and zeroes pixel memory. Pixel memory size is imageInfo.height times imageInfo.minRowBytes(). Pixel memory is deleted when Surface is deleted.

Surface is returned if all parameters are valid. Valid parameters include: info dimensions are greater than zero; info contains Image Color Type and Image Alpha Type supported by Raster Surface.

Parameters

imageInfo width, height, Image Color Type, Image Alpha Type, Color Space, of Raster Surface; width and height must be greater than zero
props LCD striping orientation and setting for device independent fonts; may be nullptr

Return Value

Surface if all parameters are valid; otherwise, nullptr

Example

See Also

MakeRasterDirect MakeRasterN32Premul MakeRasterDirectReleaseProc


MakeRasterN32Premul

static sk_sp<SkSurface> MakeRasterN32Premul(int width, int height,
                                            const SkSurfaceProps* surfaceProps = nullptr)

Allocates raster Surface. Canvas returned by Surface draws directly into pixels. Allocates and zeroes pixel memory. Pixel memory size is height times width times four. Pixel memory is deleted when Surface is deleted.

Internally, sets Image Info to width, height, Native Color Type, and kPremul SkAlphaType.

Surface is returned if width and height are greater than zero.

Use to create Surface that matches SkPMColor, the native pixel arrangement on the platform. Surface drawn to output device skips converting its pixel format.

Parameters

width pixel column count; must be greater than zero
height pixel row count; must be greater than zero
surfaceProps LCD striping orientation and setting for device independent fonts; may be nullptr

Return Value

Surface if all parameters are valid; otherwise, nullptr

Example

#### Example Output ~~~~ --- -x- --- ~~~~

See Also

MakeRasterDirect MakeRasterN32Premul MakeRasterDirectReleaseProc


MakeFromBackendTexture

static sk_sp<SkSurface> MakeFromBackendTexture(GrContext* context,
                                               const GrBackendTexture& backendTexture,
                                               GrSurfaceOrigin origin, int sampleCnt,
                                               sk_sp<SkColorSpace> colorSpace,
                                               const SkSurfaceProps* surfaceProps)

Wraps a GPU-backed texture into Surface. Caller must ensure the texture is valid for the lifetime of returned Surface. If sampleCnt greater than zero, creates an intermediate MSAA Surface which is used for drawing backendTexture.

Surface is returned if all parameters are valid. backendTexture is valid if its pixel configuration agrees with colorSpace and context; for instance, if backendTexture has an sRGB configuration, then context must support sRGB, and colorSpace must be present. Further, backendTexture width and height must not exceed context capabilities, and the context must be able to support back-end textures.

If SK SUPPORT GPU is defined as zero, has no effect and returns nullptr.

Parameters

context GPU Context
backendTexture texture residing on GPU
origin one of: kBottomLeft GrSurfaceOrigin, kTopLeft GrSurfaceOrigin
sampleCnt samples per pixel, or 0 to disable full scene anti-aliasing
colorSpace range of colors
surfaceProps LCD striping orientation and setting for device independent fonts; may be nullptr

Return Value

Surface if all parameters are valid; otherwise, nullptr

Example

void draw(SkCanvas* canvas) {
    SkPaint paint;
    paint.setTextSize(32);
    GrContext* context = canvas->getGrContext();
    if (!context) {
         canvas->drawString("GPU only!", 20, 40, paint);
         return;
    }
    sk_sp gpuSurface = SkSurface::MakeFromBackendTexture(context,
            backEndTextureRenderTarget, kTopLeft_GrSurfaceOrigin, 0, nullptr, nullptr);
    auto surfaceCanvas = gpuSurface->getCanvas();
    surfaceCanvas->clear(SK_ColorWHITE);
    surfaceCanvas->drawString("GPU rocks!", 20, 40, paint);
    sk_sp image(gpuSurface->makeImageSnapshot());
    canvas->drawImage(image, 0, 0);
}

See Also

GrBackendTexture MakeFromBackendRenderTarget MakeRenderTarget


MakeFromBackendRenderTarget

static sk_sp<SkSurface> MakeFromBackendRenderTarget(GrContext* context,
                                                   const GrBackendRenderTarget& backendRenderTarget,
                                                   GrSurfaceOrigin origin,
                                                   sk_sp<SkColorSpace> colorSpace,
                                                   const SkSurfaceProps* surfaceProps)

Wraps a GPU-backed buffer into Surface. Caller must ensure render target is valid for the lifetime of returned Surface.

Surface is returned if all parameters are valid. backendRenderTarget is valid if its pixel configuration agrees with colorSpace and context; for instance, if backendRenderTarget has an sRGB configuration, then context must support sRGB, and colorSpace must be present. Further, backendRenderTarget width and height must not exceed context capabilities, and the context must be able to support back-end render targets.

If SK SUPPORT GPU is defined as zero, has no effect and returns nullptr.

Parameters

context GPU Context
backendRenderTarget GPU intermediate memory buffer
origin one of: kBottomLeft GrSurfaceOrigin, kTopLeft GrSurfaceOrigin
colorSpace range of colors
surfaceProps LCD striping orientation and setting for device independent fonts; may be nullptr

Return Value

Surface if all parameters are valid; otherwise, nullptr

Example

void draw(SkCanvas* canvas) {
    SkPaint paint;
    paint.setTextSize(32);
    GrContext* context = canvas->getGrContext();
    if (!context) {
         canvas->drawString("GPU only!", 20, 40, paint);
         return;
    }
    sk_sp gpuSurface = SkSurface::MakeFromBackendRenderTarget(context,
            backEndRenderTarget, kTopLeft_GrSurfaceOrigin, nullptr, nullptr);
    auto surfaceCanvas = gpuSurface->getCanvas();
    surfaceCanvas->clear(SK_ColorWHITE);
    surfaceCanvas->drawString("GPU rocks!", 20, 40, paint);
    sk_sp image(gpuSurface->makeImageSnapshot());
    canvas->drawImage(image, 0, 0);
}

See Also

MakeFromBackendTexture MakeRenderTarget


MakeFromBackendTextureAsRenderTarget

static sk_sp<SkSurface> MakeFromBackendTextureAsRenderTarget(GrContext* context,
                                            const GrBackendTexture& backendTexture,
                                            GrSurfaceOrigin origin, int sampleCnt,
                                            sk_sp<SkColorSpace> colorSpace,
                                            const SkSurfaceProps* surfaceProps)

Used to wrap a GPU-backed texture as a SkSurface. Skia will treat the texture as a rendering target only, but unlike NewFromBackendRenderTarget, Skia will manage and own the associated render target objects (but not the provided texture). Skia will not assume ownership of the texture and the client must ensure the texture is valid for the lifetime of the SkSurface.

If SK SUPPORT GPU is defined as zero, has no effect and returns nullptr.

Parameters

context GPU Context
backendTexture texture residing on GPU
origin one of: kBottomLeft GrSurfaceOrigin, kTopLeft GrSurfaceOrigin
sampleCnt samples per pixel, or 0 to disable full scene anti-aliasing
colorSpace range of colors
surfaceProps LCD striping orientation and setting for device independent fonts; may be nullptr

Return Value

Surface if all parameters are valid; otherwise, nullptr

Example

void draw(SkCanvas* canvas) {SkPaint paint;
    paint.setTextSize(32);
    GrContext* context = canvas->getGrContext();
    if (!context) {
         canvas->drawString("GPU only!", 20, 40, paint);
         return;
    }
    sk_sp gpuSurface = SkSurface::MakeFromBackendTextureAsRenderTarget(
            context, backEndTextureRenderTarget, kTopLeft_GrSurfaceOrigin, 0,
            nullptr, nullptr);
    auto surfaceCanvas = gpuSurface->getCanvas();
    surfaceCanvas->clear(SK_ColorWHITE);
    surfaceCanvas->drawString("GPU rocks!", 20, 40, paint);
    sk_sp image(gpuSurface->makeImageSnapshot());
    canvas->drawImage(image, 0, 0);
}

See Also

MakeFromBackendRenderTarget MakeRenderTarget


MakeRenderTarget

static sk_sp<SkSurface> MakeRenderTarget(GrContext* context, SkBudgeted budgeted,
                                         const SkImageInfo& imageInfo, int sampleCount,
                                         GrSurfaceOrigin surfaceOrigin,
                                         const SkSurfaceProps* surfaceProps,
                                         bool shouldCreateWithMips = false)

Returns offscreen Surface on GPU indicated by context. Allocates memory for pixels, based on the width, height, and Image Color Type in ImageInfo. budgeted selects whether allocation for offscreen pixels is tracked by context. imageInfo describes the pixel format in Image Color Type, and transparency in Image Alpha Type, and color matching in Color Space.

sampleCount requests the number of samples per pixel. Pass zero to disable Multi Sample Anti Aliasing. The request is rounded up to the next supported count, or rounded down if it is larger than the maximum supported count.

surfaceOrigin pins either the top-left or the bottom-left corner to the origin.

shouldCreateWithMips hints that Image returned by makeImageSnapshot is Mip Map.

If SK SUPPORT GPU is defined as zero, has no effect and returns nullptr.

Parameters

context GPU Context
budgeted one of: SkBudgeted::kNo, SkBudgeted::kYes
imageInfo width, height, Image Color Type, Image Alpha Type, Color Space; width, or height, or both, may be zero
sampleCount samples per pixel, or 0 to disable full scene anti-aliasing
surfaceOrigin one of: kBottomLeft GrSurfaceOrigin, kTopLeft GrSurfaceOrigin
surfaceProps LCD striping orientation and setting for device independent fonts; may be nullptr
shouldCreateWithMips hint that Surface will host Mip Map images

Return Value

Surface if all parameters are valid; otherwise, nullptr

Example

See Also

MakeFromBackendRenderTarget MakeFromBackendTextureAsRenderTarget


static sk_sp<SkSurface> MakeRenderTarget(GrContext* context, SkBudgeted budgeted,
                                         const SkImageInfo& imageInfo, int sampleCount,
                                         const SkSurfaceProps* props)

Returns offscreen Surface on GPU indicated by context. Allocates memory for pixels, based on the width, height, and Image Color Type in ImageInfo. budgeted selects whether allocation for offscreen pixels is tracked by context. imageInfo describes the pixel format in Image Color Type, and transparency in Image Alpha Type, and color matching in Color Space.

sampleCount requests the number of samples per pixel. Pass zero to disable Multi Sample Anti Aliasing. The request is rounded up to the next supported count, or rounded down if it is larger than the maximum supported count.

Surface bottom-left corner is pinned to the origin.

Parameters

context GPU Context
budgeted one of: SkBudgeted::kNo, SkBudgeted::kYes
imageInfo width, height, Image Color Type, Image Alpha Type, Color Space, of Raster Surface; width, or height, or both, may be zero
sampleCount samples per pixel, or 0 to disable Multi Sample Anti Aliasing
props LCD striping orientation and setting for device independent fonts; may be nullptr

Return Value

Surface if all parameters are valid; otherwise, nullptr

Example

LCD text takes advantage of raster striping to improve resolution. Only one of the four combinations is correct, depending on whether the monitor's LCD is horizontal or vertical, and whether the order of the stripes is red blue green or red green blue.

See Also

MakeFromBackendRenderTarget MakeFromBackendTextureAsRenderTarget


static sk_sp<SkSurface> MakeRenderTarget(GrContext* context, SkBudgeted budgeted,
                                         const SkImageInfo& imageInfo)

Returns offscreen Surface on GPU indicated by context. Allocates memory for pixels, based on the width, height, and Image Color Type in ImageInfo. budgeted selects whether allocation for offscreen pixels is tracked by context. imageInfo describes the pixel format in Image Color Type, and transparency in Image Alpha Type, and color matching in Color Space.

Surface bottom-left corner is pinned to the origin.

Parameters

context GPU Context
budgeted one of: SkBudgeted::kNo, SkBudgeted::kYes
imageInfo width, height, Image Color Type, Image Alpha Type, Color Space, of Raster Surface; width, or height, or both, may be zero

Return Value

Surface if all parameters are valid; otherwise, nullptr

Example

See Also

MakeFromBackendRenderTarget MakeFromBackendTextureAsRenderTarget


MakeNull

static sk_sp<SkSurface> MakeNull(int width, int height)

Returns Surface without backing pixels. Drawing to Canvas returned from Surface has no effect. Calling makeImageSnapshot on returned Surface returns nullptr.

Parameters

width one or greater
height one or greater

Return Value

Surface if width and height are positive; otherwise, nullptr

Example

#### Example Output ~~~~ SkSurface::MakeNull(0, 0) == nullptr surf->makeImageSnapshot() == nullptr ~~~~

See Also

MakeRaster MakeRenderTarget


width

int width() const

Returns pixel count in each row; may be zero or greater.

Return Value

number of pixel columns

Example

#### Example Output ~~~~ surface width=37 canvas width=37 ~~~~

See Also

height


height

int height() const

Returns pixel row count; may be zero or greater.

Return Value

number of pixel rows

Example

#### Example Output ~~~~ surface height=1000 canvas height=1000 ~~~~

See Also

width


generationID

uint32_t generationID()

Returns unique value identifying the content of Surface. Returned value changes each time the content changes. Content is changed by drawing, or by calling notifyContentWillChange.

Return Value

unique content identifier

Example

#### Example Output ~~~~ surface generationID: 1 surface generationID: 2 surface generationID: 3 ~~~~

See Also

notifyContentWillChange ContentChangeMode getCanvas


Enum SkSurface::ContentChangeMode

enum ContentChangeMode {
kDiscard ContentChangeMode,
kRetain ContentChangeMode,
};

ContentChangeMode members are parameters to notifyContentWillChange.

Constants

SkSurface::kDiscard_ContentChangeMode Pass to notifyContentWillChange to discard surface contents whenthe surface is cleared or overwritten.
SkSurface::kRetain_ContentChangeMode Pass to notifyContentWillChange when to preserve surface contents.If a snapshot has been generated, this copies the Surface contents.

See Also

notifyContentWillChange generationID

notifyContentWillChange

void notifyContentWillChange(ContentChangeMode mode)

Notifies that Surface contents will be changed by code outside of Skia. Subsequent calls to generationID return a different value.

mode is normally passed as kRetain ContentChangeMode.

Parameters

mode one of: kDiscard ContentChangeMode, kRetain ContentChangeMode

Example

See Also

ContentChangeMode generationID


Enum SkSurface::BackendHandleAccess

enum BackendHandleAccess {
kFlushRead BackendHandleAccess,
kFlushWrite BackendHandleAccess,
kDiscardWrite BackendHandleAccess,
};

Constants

SkSurface::kFlushRead_BackendHandleAccess 0Caller may read from the back-end object.
SkSurface::kFlushWrite_BackendHandleAccess 1Caller may write to the back-end object.
SkSurface::kDiscardWrite_BackendHandleAccess 2Caller must overwrite the entire back-end object.

Example

See Also

getTextureHandle getRenderTargetHandle

getTextureHandle

GrBackendObject getTextureHandle(BackendHandleAccess backendHandleAccess)

Returns the GPU back-end reference of the texture used by Surface, or zero if Surface is not backed by a GPU texture.

The returned texture handle is only valid until the next draw into Surface, or when Surface is deleted.

Parameters

backendHandleAccess one of: kFlushRead BackendHandleAccess, kFlushWrite BackendHandleAccess, kDiscardWrite BackendHandleAccess

Return Value

GPU texture reference

Example

See Also

getRenderTargetHandle GrBackendObject BackendHandleAccess


getRenderTargetHandle

bool getRenderTargetHandle(GrBackendObject* backendObject, BackendHandleAccess backendHandleAccess)

Returns true and stores the GPU back-end reference of the render target used by Surface in backendObject.

Return false if Surface is not backed by a GPU render target, and leaves backendObject unchanged.

The returned render target handle is only valid until the next draw into Surface, or when Surface is deleted.

In OpenGL this returns the frame buffer object ID.

Parameters

backendObject GPU intermediate memory buffer
backendHandleAccess one of: kFlushRead BackendHandleAccess, kFlushWrite BackendHandleAccess, kDiscardWrite BackendHandleAccess

Return Value

true if Surface is backed by GPU texture

Example

See Also

getTextureHandle GrBackendObject BackendHandleAccess


getCanvas

SkCanvas* getCanvas()

Returns Canvas that draws into Surface. Subsequent calls return the same Canvas. Canvas returned is managed and owned by Surface, and is deleted when Surface is deleted.

Return Value

drawing Canvas for Surface

Example

See Also

makeSurface makeImageSnapshot draw


makeSurface

sk_sp<SkSurface> makeSurface(const SkImageInfo& imageInfo)

Returns a compatible Surface, or nullptr. Returned Surface contains the same raster, GPU, or null properties as the original. Returned Surface does not share the same pixels.

Returns nullptr if imageInfo width or height are zero, or if imageInfo is incompatible with Surface.

Parameters

imageInfo width, height, Image Color Type, Image Alpha Type, Color Space, of Surface; width and height must be greater than zero

Return Value

compatible Surface or nullptr

Example

See Also

makeImageSnapshot getCanvas draw


makeImageSnapshot

sk_sp<SkImage> makeImageSnapshot()

Returns Image capturing Surface contents. Subsequent drawing to Surface contents are not captured. Image allocation is accounted for if Surface was created with SkBudgeted::kYes.

Return Value

Image initialized with Surface contents

Example

See Also

draw getCanvas


draw

void draw(SkCanvas* canvas, SkScalar x, SkScalar y, const SkPaint* paint)

Draws Surface contents to canvas, with its top-left corner at (x, y).

If Paint paint is not nullptr, apply Color Filter, Color Alpha, Image Filter, Blend Mode, and Draw Looper.

Parameters

canvas Canvas drawn into
x horizontal offset in Canvas
y vertical offset in Canvas
paint Paint containing Blend Mode, Color Filter, Image Filter, and so on; or nullptr

Example

See Also

makeImageSnapshot getCanvas


peekPixels

bool peekPixels(SkPixmap* pixmap)

Copies Surface pixel address, row bytes, and Image Info to Pixmap, if address is available, and returns true. If pixel address is not available, return false and leave Pixmap unchanged.

pixmap contents become invalid on any future change to Surface.

Parameters

pixmap storage for pixel state if pixels are readable; otherwise, ignored

Return Value

true if Surface has direct access to pixels

Example

See Also

readPixels


readPixels

bool readPixels(const SkPixmap& dst, int srcX, int srcY)

Copies Rect of pixels to dst.

Source Rect corners are (srcX, srcY) and (this->width, this->height). Destination Rect corners are (0, 0) and (dst.width, dst.height). Copies each readable pixel intersecting both rectangles, without scaling, converting to dst.colorType() and dst.alphaType() if required.

Pixels are readable when Surface is raster, or backed by a GPU.

The destination pixel storage must be allocated by the caller.

Pixel values are converted only if Image Color Type and Image Alpha Type do not match. Only pixels within both source and destination rectangles are copied. dst contents outside Rect intersection are unchanged.

Pass negative values for srcX or srcY to offset pixels across or down destination.

Does not copy, and returns false if:

Source and destination rectangles do not intersect.
Pixmap pixels could not be allocated.
dst.rowBytes() is too small to contain one row of pixels.

Parameters

dst storage for pixels copied from Surface
srcX offset into readable pixels in x; may be negative
srcY offset into readable pixels in y; may be negative

Return Value

true if pixels were copied

Example

See Also

peekPixels


bool readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes, int srcX, int srcY)

Copies Rect of pixels from Canvas into dstPixels.

Source Rect corners are (srcX, srcY) and (this->width, this->height). Destination Rect corners are (0, 0) and (dstInfo.width, dstInfo.height). Copies each readable pixel intersecting both rectangles, without scaling, converting to dstInfo.colorType() and dstInfo.alphaType() if required.

Pixels are readable when Surface is raster, or backed by a GPU.

The destination pixel storage must be allocated by the caller.

Pixel values are converted only if Image Color Type and Image Alpha Type do not match. Only pixels within both source and destination rectangles are copied. dstPixels contents outside Rect intersection are unchanged.

Pass negative values for srcX or srcY to offset pixels across or down destination.

Does not copy, and returns false if:

Source and destination rectangles do not intersect.
Surface pixels could not be converted to dstInfo.colorType() or dstInfo.alphaType().
dstRowBytes is too small to contain one row of pixels.

Parameters

dstInfo width, height, Image Color Type, and Image Alpha Type of dstPixels
dstPixels storage for pixels; dstInfo.height times dstRowBytes, or larger
dstRowBytes size of one destination row; dstInfo.width times pixel size, or larger
srcX offset into readable pixels in x; may be negative
srcY offset into readable pixels in y; may be negative

Return Value

true if pixels were copied

Example

A black oval drawn on a red background provides an image to copy. readPixels copies one quarter of the Surface into each of the four corners. The copied quarter ovals overdraw the original oval.

See Also

peekPixels


bool readPixels(const SkBitmap& dst, int srcX, int srcY)

Copies Rect of pixels from Surface into bitmap.

Source Rect corners are (srcX, srcY) and (this->width, this->height). Destination Rect corners are (0, 0) and (bitmap.width, bitmap.height). Copies each readable pixel intersecting both rectangles, without scaling, converting to bitmap.colorType() and bitmap.alphaType() if required.

Pixels are readable when Surface is raster, or backed by a GPU.

The destination pixel storage must be allocated by the caller.

Pixel values are converted only if Image Color Type and Image Alpha Type do not match. Only pixels within both source and destination rectangles are copied. dst contents outside Rect intersection are unchanged.

Pass negative values for srcX or srcY to offset pixels across or down destination.

Does not copy, and returns false if:

Source and destination rectangles do not intersect.
Surface pixels could not be converted to dst.colorType() or dst.alphaType().
dst pixels could not be allocated.
dst.rowBytes() is too small to contain one row of pixels.

Parameters

dst storage for pixels copied from Surface
srcX offset into readable pixels in x; may be negative
srcY offset into readable pixels in y; may be negative

Return Value

true if pixels were copied

Example

See Also

peekPixels


props

const SkSurfaceProps& props() const

Returns Surface Properties for surface.

Return Value

LCD striping orientation and setting for device independent fonts

Example

#### Example Output ~~~~ surf.props(): kRGB_H_SkPixelGeometry ~~~~

See Also

SkSurfaceProps


prepareForExternalIO

void prepareForExternalIO()

To be deprecated.


flush

void flush()

Issues pending Surface commands to the GPU-backed API and resolves any Surface MSAA.

Skia flushes as needed, so it is not necessary to call this if Skia manages drawing and object lifetime. Call when interleaving Skia calls with native GPU calls.

See Also

GrBackendSemaphore


flushAndSignalSemaphores

GrSemaphoresSubmitted flushAndSignalSemaphores(int numSemaphores,
                                               GrBackendSemaphore signalSemaphores[])

Issues pending Surface commands to the GPU-backed API and resolves any Surface MSAA. After issuing all commands, signalSemaphores of count numSemaphores semaphores are signaled by the GPU.

For each GrBackendSemaphore in signalSemaphores: if GrBackendSemaphore is initialized, the GPU back-end uses the semaphore as is; otherwise, a new semaphore is created and initializes GrBackendSemaphore.

The caller must delete the semaphores created and returned in signalSemaphores. GrBackendSemaphore can be deleted as soon as this function returns.

If the back-end API is OpenGL only uninitialized GrBackendSemaphores are supported.

If the back-end API is Vulkan semaphores may be initialized or uninitialized. If uninitialized, created semaphores are valid only with the VkDevice with which they were created.

If GrSemaphoresSubmitted::kNo is returned, the GPU back-end did not create or add any semaphores to signal on the GPU; the caller should not instruct the GPU to wait on any of the semaphores.

Pending surface commands are flushed regardless of the return result.

Parameters

numSemaphores size of signalSemaphores array
signalSemaphores array of semaphore containers

Return Value

one of: GrSemaphoresSubmitted::kYes, GrSemaphoresSubmitted::kNo

See Also

wait GrBackendSemaphore


wait

bool wait(int numSemaphores, const GrBackendSemaphore* waitSemaphores)

Inserts a list of GPU semaphores that the current GPU-backed API must wait on before executing any more commands on the GPU for this surface. Skia will take ownership of the underlying semaphores and delete them once they have been signaled and waited on. If this call returns false, then the GPU back-end will not wait on any passed in semaphores, and the client will still own the semaphores.

Parameters

numSemaphores size of waitSemaphores array
waitSemaphores array of semaphore containers

Return Value

true if GPU is waiting on semaphores

Example

See Also

flushAndSignalSemaphores GrBackendSemaphore


characterize

bool characterize(SkSurfaceCharacterization* characterization) const

Initializes Surface Characterization that can be used to perform GPU back-end pre-processing in a separate thread. Typically this is used to divide drawing into multiple tiles. DeferredDisplayListRecorder records the drawing commands for each tile.

Return true if Surface supports characterization. Raster Surface returns false.

Parameters

characterization properties for parallel drawing

Return Value

true if supported

Example

See Also

draw SkSurfaceCharacterization SkDeferredDisplayList


void draw(SkDeferredDisplayList* deferredDisplayList)

Draws deferred display list created using SkDeferredDisplayListRecorder. The draw has no effect if Surface Characterization stored in deferredDisplayList is not compatible with Surface.

Parameters

deferredDisplayList drawing commands

Example

See Also

characterize SkSurfaceCharacterization SkDeferredDisplayList