flutter::ImageDescriptor Class Reference

Creates an image descriptor for encoded or decoded image data, describing the width, height, and bytes per pixel for that image. This class will hold a reference on the underlying image data, and in the case of compressed data, an ImageGenerator for the data. The Codec initialization actually happens in initEncoded, making initstantiateCodec a lightweight operation. More...

#include <image_descriptor.h>

Inheritance diagram for flutter::ImageDescriptor:

Public Types
enum	PixelFormat { kRGBA8888 , kBGRA8888 , kRGBAFloat32 }
Public Types inherited from tonic::DartWrappable
enum	DartNativeFields { kPeerIndex , kNumberOfNativeFields }

Public Member Functions
	~ImageDescriptor () override=default
void	instantiateCodec (Dart_Handle codec, int target_width, int target_height)
	Associates a flutter::Codec object with the dart.ui Codec handle.
int	width () const
	The width of this image, EXIF oriented if applicable.
int	height () const
	The height of this image. EXIF oriented if applicable.
int	bytesPerPixel () const
	The bytes per pixel of the image.
int	row_bytes () const
	The byte length of the first row of the image. Defaults to width() * 4.
bool	should_resize (int target_width, int target_height) const
	Whether the given target_width or target_height differ from width() and height() respectively.
sk_sp< SkData >	data () const
	The underlying buffer for this image.
sk_sp< SkImage >	image () const
bool	is_compressed () const
	Whether this descriptor represents compressed (encoded) data or not.
const SkImageInfo &	image_info () const
	The orientation corrected image info for this image.
SkISize	get_scaled_dimensions (float scale)
	Gets the scaled dimensions of this image, if backed by an ImageGenerator that can perform efficient subpixel scaling.
bool	get_pixels (const SkPixmap &pixmap) const
	Gets pixels for this image transformed based on the EXIF orientation tag, if applicable.
void	dispose ()
Public Member Functions inherited from flutter::RefCountedDartWrappable< ImageDescriptor >
virtual void	RetainDartWrappableReference () const override
virtual void	ReleaseDartWrappableReference () const override
Public Member Functions inherited from fml::RefCountedThreadSafe< T >
void	Release () const
Public Member Functions inherited from fml::internal::RefCountedThreadSafeBase
void	AddRef () const
bool	HasOneRef () const
void	AssertHasOneRef () const
Public Member Functions inherited from tonic::DartWrappable
	DartWrappable ()
virtual const DartWrapperInfo &	GetDartWrapperInfo () const =0
Dart_Handle	CreateDartWrapper (DartState *dart_state)
void	AssociateWithDartWrapper (Dart_Handle wrappable)
void	ClearDartWrapper ()
Dart_WeakPersistentHandle	dart_wrapper () const

Static Public Member Functions
static Dart_Handle	initEncoded (Dart_Handle descriptor_handle, ImmutableBuffer *immutable_buffer, Dart_Handle callback_handle)
	Asynchronously initializes an ImageDescriptor for an encoded image, as long as the format is recognized by an encoder installed in the ImageGeneratorRegistry. Calling this method will create an ImageGenerator and read EXIF corrected dimensions from the image data.
static void	initRaw (Dart_Handle descriptor_handle, const fml::RefPtr< ImmutableBuffer > &data, int width, int height, int row_bytes, PixelFormat pixel_format)
	Synchronously initializes an ImageDescriptor for decompressed image data as specified by the PixelFormat.

Friends
class	ImageDecoderFixtureTest

Additional Inherited Members
Protected Member Functions inherited from fml::RefCountedThreadSafe< T >
	RefCountedThreadSafe ()
	~RefCountedThreadSafe ()
Protected Member Functions inherited from fml::internal::RefCountedThreadSafeBase
	RefCountedThreadSafeBase ()
	~RefCountedThreadSafeBase ()
bool	Release () const
void	Adopt ()
Protected Member Functions inherited from tonic::DartWrappable
virtual	~DartWrappable ()
Static Protected Member Functions inherited from tonic::DartWrappable
static Dart_PersistentHandle	GetTypeForWrapper (tonic::DartState *dart_state, const tonic::DartWrapperInfo &wrapper_info)

Detailed Description

Creates an image descriptor for encoded or decoded image data, describing the width, height, and bytes per pixel for that image. This class will hold a reference on the underlying image data, and in the case of compressed data, an ImageGenerator for the data. The Codec initialization actually happens in initEncoded, making initstantiateCodec a lightweight operation.

See also

ImageGenerator

Definition at line 32 of file image_descriptor.h.

Member Enumeration Documentation

PixelFormat

enum flutter::ImageDescriptor::PixelFormat

Enumerator
kRGBA8888
kBGRA8888
kRGBAFloat32

Definition at line 37 of file image_descriptor.h.

                   {
    kRGBA8888,
    kBGRA8888,
    kRGBAFloat32,
  };

Constructor & Destructor Documentation

~ImageDescriptor()

flutter::ImageDescriptor::~ImageDescriptor ( )

overridedefault

Member Function Documentation

bytesPerPixel()

int flutter::ImageDescriptor::bytesPerPixel ( ) const

inline

The bytes per pixel of the image.

Definition at line 72 of file image_descriptor.h.

{ return image_info_.bytesPerPixel(); }

data()

sk_sp< SkData > flutter::ImageDescriptor::data ( ) const

inline

The underlying buffer for this image.

Definition at line 88 of file image_descriptor.h.

{ return buffer_; }

dispose()

void flutter::ImageDescriptor::dispose ( )

inline

Definition at line 113 of file image_descriptor.h.

                 {
    buffer_.reset();
    generator_.reset();
    ClearDartWrapper();
  }

get_pixels()

bool flutter::ImageDescriptor::get_pixels

(

const SkPixmap &

pixmap

)

const

Gets pixels for this image transformed based on the EXIF orientation tag, if applicable.

Definition at line 128 of file image_descriptor.cc.

                                                             {
  FML_DCHECK(generator_);
  return generator_->GetPixels(pixmap.info(), pixmap.writable_addr(),
                               pixmap.rowBytes());
}

get_scaled_dimensions()

SkISize flutter::ImageDescriptor::get_scaled_dimensions ( float  scale )

inline

Gets the scaled dimensions of this image, if backed by an ImageGenerator that can perform efficient subpixel scaling.

See also

ImageGenerator::GetScaledDimensions

Definition at line 102 of file image_descriptor.h.

                                             {
    if (generator_) {
      return generator_->GetScaledDimensions(scale);
    }
    return image_info_.dimensions();
  }

height()

int flutter::ImageDescriptor::height ( ) const

inline

The height of this image. EXIF oriented if applicable.

Definition at line 69 of file image_descriptor.h.

{ return image_info_.height(); }

image()

sk_sp< SkImage > flutter::ImageDescriptor::image

(

)

const

Definition at line 124 of file image_descriptor.cc.

                                            {
  return generator_->GetImage();
}

image_info()

const SkImageInfo & flutter::ImageDescriptor::image_info ( ) const

inline

The orientation corrected image info for this image.

Definition at line 97 of file image_descriptor.h.

{ return image_info_; }

initEncoded()

Dart_Handle flutter::ImageDescriptor::initEncoded ( Dart_Handle  descriptor_handle, ImmutableBuffer *  immutable_buffer, Dart_Handle  callback_handle  )

static

Asynchronously initializes an ImageDescriptor for an encoded image, as long as the format is recognized by an encoder installed in the ImageGeneratorRegistry. Calling this method will create an ImageGenerator and read EXIF corrected dimensions from the image data.

See also

ImageGeneratorRegistry

Definition at line 40 of file image_descriptor.cc.

                                                                      {
  if (!Dart_IsClosure(callback_handle)) {
    return tonic::ToDart("Callback must be a function");
  }
 
  if (!immutable_buffer) {
    return tonic::ToDart("Buffer parameter must not be null");
  }
 
  // This has to be valid because this method is called from Dart.
  auto dart_state = UIDartState::Current();
  auto registry = dart_state->GetImageGeneratorRegistry();
 
  if (!registry) {
    return tonic::ToDart(
        "Failed to access the internal image decoder "
        "registry on this isolate. Please file a bug on "
        "https://github.com/flutter/flutter/issues.");
  }
 
  auto generator =
      registry->CreateCompatibleGenerator(immutable_buffer->data());
 
  if (!generator) {
    // No compatible image decoder was found.
    return tonic::ToDart("Invalid image data");
  }
 
  auto descriptor = fml::MakeRefCounted<ImageDescriptor>(
      immutable_buffer->data(), std::move(generator));
 
  FML_DCHECK(descriptor);
 
  descriptor->AssociateWithDartWrapper(descriptor_handle);
  tonic::DartInvoke(callback_handle, {Dart_TypeVoid()});
 
  return Dart_Null();
}

initRaw()

void flutter::ImageDescriptor::initRaw ( Dart_Handle  descriptor_handle, const fml::RefPtr< ImmutableBuffer > &  data, int  width, int  height, int  row_bytes, PixelFormat  pixel_format  )

static

Synchronously initializes an ImageDescriptor for decompressed image data as specified by the PixelFormat.

Definition at line 81 of file image_descriptor.cc.

                                                        {
  SkColorType color_type = kUnknown_SkColorType;
  SkAlphaType alpha_type = kPremul_SkAlphaType;
  switch (pixel_format) {
    case PixelFormat::kRGBA8888:
      color_type = kRGBA_8888_SkColorType;
      break;
    case PixelFormat::kBGRA8888:
      color_type = kBGRA_8888_SkColorType;
      break;
    case PixelFormat::kRGBAFloat32:
      // `PixelFormat.rgbaFloat32` is documented to not use premultiplied alpha.
      color_type = kRGBA_F32_SkColorType;
      alpha_type = kUnpremul_SkAlphaType;
      break;
  }
  FML_DCHECK(color_type != kUnknown_SkColorType);
  auto image_info = SkImageInfo::Make(width, height, color_type, alpha_type);
  auto descriptor = fml::MakeRefCounted<ImageDescriptor>(
      data->data(), std::move(image_info),
      row_bytes == -1 ? std::nullopt : std::optional<size_t>(row_bytes));
  descriptor->AssociateWithDartWrapper(descriptor_handle);
}

instantiateCodec()

void flutter::ImageDescriptor::instantiateCodec	(	Dart_Handle	codec,
		int	target_width,
		int	target_height
	)

Associates a flutter::Codec object with the dart.ui Codec handle.

Definition at line 110 of file image_descriptor.cc.

                                                          {
  fml::RefPtr<Codec> ui_codec;
  if (!generator_ || generator_->GetFrameCount() == 1) {
    ui_codec = fml::MakeRefCounted<SingleFrameCodec>(
        static_cast<fml::RefPtr<ImageDescriptor>>(this), target_width,
        target_height);
  } else {
    ui_codec = fml::MakeRefCounted<MultiFrameCodec>(generator_);
  }
  ui_codec->AssociateWithDartWrapper(codec_handle);
}

is_compressed()

bool flutter::ImageDescriptor::is_compressed ( ) const

inline

Whether this descriptor represents compressed (encoded) data or not.

Definition at line 94 of file image_descriptor.h.

{ return !!generator_; }

row_bytes()

int flutter::ImageDescriptor::row_bytes ( ) const

inline

The byte length of the first row of the image. Defaults to width() * 4.

Definition at line 76 of file image_descriptor.h.

                        {
    return row_bytes_.value_or(
        static_cast<size_t>(image_info_.width() * image_info_.bytesPerPixel()));
  }

should_resize()

bool flutter::ImageDescriptor::should_resize ( int  target_width, int  target_height  ) const

inline

Whether the given target_width or target_height differ from width() and height() respectively.

Definition at line 83 of file image_descriptor.h.

                                                                {
    return target_width != width() || target_height != height();
  }

width()

int flutter::ImageDescriptor::width ( ) const

inline

The width of this image, EXIF oriented if applicable.

Definition at line 66 of file image_descriptor.h.

{ return image_info_.width(); }

Friends And Related Symbol Documentation

ImageDecoderFixtureTest

friend class ImageDecoderFixtureTest

friend

Definition at line 137 of file image_descriptor.h.

---

The documentation for this class was generated from the following files:

• lib/ui/painting/image_descriptor.h
• lib/ui/painting/image_descriptor.cc