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remove Sampling extensions from Flutter API, but remove as much relia…
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…nce on SkFilterQuality as can currently be achieved
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@flar
flar committed Mar 19, 2021
1 parent 7ee51f9 commit ef24722
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Showing 12 changed files with 132 additions and 362 deletions.
4 changes: 2 additions & 2 deletions lib/ui/compositing.dart
View file
Expand Up @@ -545,7 +545,7 @@ class SceneBuilder extends NativeFieldWrapperClass2 {
maskRect.top,
maskRect.bottom,
blendMode.index,
filterQuality._nativeIndex,
filterQuality.index,
oldLayer?._nativeLayer,
);
final ShaderMaskEngineLayer layer = ShaderMaskEngineLayer._(engineLayer);
Expand Down Expand Up @@ -731,7 +731,7 @@ class SceneBuilder extends NativeFieldWrapperClass2 {
FilterQuality filterQuality = FilterQuality.low,
}) {
assert(offset != null, 'Offset argument was null'); // ignore: unnecessary_null_comparison
_addTexture(offset.dx, offset.dy, width, height, textureId, freeze, filterQuality._nativeIndex);
_addTexture(offset.dx, offset.dy, width, height, textureId, freeze, filterQuality.index);
}

void _addTexture(double dx, double dy, double width, double height, int textureId, bool freeze,
Expand Down
5 changes: 2 additions & 3 deletions lib/ui/compositing/scene_builder.cc
View file
Expand Up @@ -232,8 +232,7 @@ void SceneBuilder::pushShaderMask(Dart_Handle layer_handle,
fml::RefPtr<EngineLayer> oldLayer) {
SkRect rect = SkRect::MakeLTRB(maskRectLeft, maskRectTop, maskRectRight,
maskRectBottom);
SkSamplingOptions sampling =
ImageFilter::fromFilterQualityIndex(filterQualityIndex);
auto sampling = ImageFilter::SamplingFromIndex(filterQualityIndex);
auto layer = std::make_shared<flutter::ShaderMaskLayer>(
shader->shader(sampling), rect, static_cast<SkBlendMode>(blendMode));
PushLayer(layer);
Expand Down Expand Up @@ -288,7 +287,7 @@ void SceneBuilder::addTexture(double dx,
int64_t textureId,
bool freeze,
int filterQualityIndex) {
auto sampling = ImageFilter::fromFilterQualityIndex(filterQualityIndex);
auto sampling = ImageFilter::SamplingFromIndex(filterQualityIndex);
auto layer = std::make_unique<flutter::TextureLayer>(
SkPoint::Make(dx, dy), SkSize::Make(width, height), textureId, freeze,
sampling);
Expand Down
207 changes: 41 additions & 166 deletions lib/ui/painting.dart
View file
Expand Up @@ -823,72 +823,19 @@ enum BlendMode {
luminosity,
}

/// Method for sampling bitmaps when the bitmap pixels do not line up exactly on device pixels.
enum BitmapFilterSampling {
// This list comes from SkFilterMode in SkSamplingOptions.h and the values (order) should
// be kept in sync.

/// Choose the nearest pixel to the sample location.
///
/// This technique can make the image look blocky when scaled up in size.
nearest,

/// Linearly blend between the nearest 2 or 4 pixels to the sample location.
///
/// This technique is much smoother than [nearest] with only a modest performance impact
/// on modern hardware.
bilinear,
}

/// Method for using an optional mipmap to improve quality when scaling an image to less
/// than half of its original size.
///
/// A mipmap is a series of images at multiple resolutions - typically each half of the
/// next larger resolution - that allows a sampling algorithm to choose an image that is
/// closer to the rendering scale to reduce the amount of missing detail when scaling
/// down by ratios a lot less than 50%.
enum MipmapFilterSampling {
// This list comes from SkMipmapMode in SkSamplingOptions.h and the values (order) should
// be kept in sync.

/// Do not use a mipmap.
///
/// All samples will come from the full-sized version of the bitmap using any associated
/// [BitmapFilterSampling] specified.
none,

/// Choose the nearest scale level in the bitmap's mipmap.
///
/// First the operation chooses the mipmap that is closest in scale to the 2D scale at
/// the given sample position and then uses the specified [BitmapFilterSampling] to sample
/// from that chosen bitmap.
nearest,

/// Choose the two nearest scale levels in the bitmap's mipmap and linearly blend
/// matching pixel samples from each into a single result.
///
/// First the operation chooses the two mipmap levels that bracket the 2D scale at the
/// given sample position, uses the specified [BitmapFilterSampling] to get a sample from
/// each of those chosen bitmaps, and then linear interpolates between those two mipmap
/// samples depending on how close the sample scale was to the scales of each mipmap level.
bilinear,
}

/// Quality levels for image sampling in [ImageFilter] and [Shader] objects that sample
/// images and for [Canvas] operations that render images.
///
/// A few instances of this class are provided as class constants to make it easier
/// to quickly dial in a reasonable level of quality for most operations.
///
/// When scaling up typically the quality is lowest at [none], higher at [low] and [medium],
/// and the highest at [high].
/// and for very large scale factors (over 10x) the highest at [high].
///
/// When scaling down, the higher the scale factor the less effective the [high]
/// level is. Beyond a certain scale level [medium] may provide better visual
/// result than [high].
/// When scaling down, [medium] provides the best quality especially when scaling an
/// image to less than half its size or for animating the scale factor between such
/// reductions. Otherwise, [low] and [high] provide similar effects for reductions of
/// between 50% and 100% but the image may lose detail and have dropouts below 50%.
///
/// To get high quality when scaling images up and down, or when the scale is
/// unknown, [medium] is typically a good enough choice.
/// unknown, [medium] is typically a good balanced choice.
///
/// ![](https://flutter.github.io/assets-for-api-docs/assets/dart-ui/filter_quality.png)
///
Expand All @@ -906,120 +853,52 @@ enum MipmapFilterSampling {
/// * [Canvas.drawImageRect].
/// * [Canvas.drawImageNine].
/// * [Canvas.drawAtlas].
abstract class FilterQuality {
enum FilterQuality {
// This list and the values (order) should be kept in sync with the equivalent list
// in lib/ui/painting/image_filter.cc

/// The fastest filtering method, albeit also the lowest quality.
///
/// This value is equivalent to a mipmap filter using
/// [BitmapFilterSampling.nearest] and [MipmapFilterSampling.none].
static const FilterQuality none = FilterQuality.mipmap(
bitmapSampling: BitmapFilterSampling.nearest,
mipmapSampling: MipmapFilterSampling.none,
);
/// This value results in a "Nearest Neighbor" algorithm which just
/// repeats or eliminates pixels as an image is scaled up or down.
none,

/// Better quality than [none], faster than [medium].
///
/// This value is equivalent to a mipmap filter using
/// [BitmapFilterSampling.bilinear] and [MipmapFilterSampling.none].
static const FilterQuality low = FilterQuality.mipmap(
bitmapSampling: BitmapFilterSampling.bilinear,
mipmapSampling: MipmapFilterSampling.none,
);
/// This value results in a "Bilinear" algorithm which smoothly
/// interpolates between pixels in an image.
low,

/// When scaling down images, this is frequently better than [high].
/// The best all around filtering method that is only worse than [high]
/// at extremely large scale factors.
///
/// This value is equivalent to a mipmap filter using
/// [BitmapFilterSampling.bilinear] and [MipmapFilterSampling.bilinear].
/// This value improves upon the "Bilinear" algorithm specified by [low]
/// by utilizing a Mipmap that pre-computes high quality lower resolutions
/// of the image at half (and quarter and eighth, etc.) sizes and then
/// blends between those to prevent loss of detail at small scale sizes.
///
/// {@template dart.ui.filterQuality.seeAlso}
/// See also:
///
/// * [FilterQuality] class-level documentation that goes into detail about
/// relative qualities of the constant values.
/// {@endtemplate}
static const FilterQuality medium = FilterQuality.mipmap(
bitmapSampling: BitmapFilterSampling.bilinear,
mipmapSampling: MipmapFilterSampling.bilinear,
);
medium,

/// Best possible quality when scaling up images.
/// Best possible quality when scaling up images by scale factors larger than
/// 5-10x.
///
/// When images are scaled down, this can be worse than [medium] for scales
/// smaller than 0.5x.
/// smaller than 0.5x, or when animating the scale factor.
///
/// This option is the slowest.
/// This option is also the slowest.
///
/// This value is equivalent to [FilterQuality.cubic].
/// This value results in a standard "Bicubic" algorithm which uses a 3rd order
/// equation to smooth the abrupt transitions between pixels while preserving
/// some of the sense of an edge and avoiding sharp peaks in the result.
///
/// {@macro dart.ui.filterQuality.seeAlso}
static const FilterQuality high = FilterQuality.cubic();

/// Creates a FilterQuality with the specified [BitmapFilterSampling] method and
/// an optional [MipmapFilterSampling] method.
const factory FilterQuality.mipmap({
required BitmapFilterSampling bitmapSampling,
MipmapFilterSampling mipmapSampling,
}) = _MipmapFilterQuality;

/// Creates a FilterQuality that specifies the use of a [Mitchell-Netravali cubic interpolation
/// function](https://en.wikipedia.org/wiki/Mitchell%E2%80%93Netravali_filters) with the standard
/// coefficients recommended by the authors of `(B=1.0/3.0, C=1.0/3.0)`.
const factory FilterQuality.cubic() = _CubicFilterQuality;

int get _nativeIndex;
}

// This list and the values (order) should be kept in sync with the equivalent list
// in lib/ui/painting/paint.cc
const List<FilterQuality> _filterQualitiesFromNative = <FilterQuality>[
FilterQuality.mipmap(bitmapSampling: BitmapFilterSampling.nearest, mipmapSampling: MipmapFilterSampling.none),
FilterQuality.mipmap(bitmapSampling: BitmapFilterSampling.bilinear, mipmapSampling: MipmapFilterSampling.none),
FilterQuality.mipmap(bitmapSampling: BitmapFilterSampling.nearest, mipmapSampling: MipmapFilterSampling.nearest),
FilterQuality.mipmap(bitmapSampling: BitmapFilterSampling.bilinear, mipmapSampling: MipmapFilterSampling.nearest),
FilterQuality.mipmap(bitmapSampling: BitmapFilterSampling.nearest, mipmapSampling: MipmapFilterSampling.bilinear),
FilterQuality.mipmap(bitmapSampling: BitmapFilterSampling.bilinear, mipmapSampling: MipmapFilterSampling.bilinear),
FilterQuality.cubic(),
];

class _MipmapFilterQuality implements FilterQuality {
const _MipmapFilterQuality({ required this.bitmapSampling, this.mipmapSampling = MipmapFilterSampling.none });

final BitmapFilterSampling bitmapSampling;
final MipmapFilterSampling mipmapSampling;

@override
int get _nativeIndex {
final int index = mipmapSampling.index * 2 + bitmapSampling.index;
assert(_filterQualitiesFromNative[index] == this);
return index;
}

@override
bool operator ==(Object other) =>
identical(this, other) ||
other is _MipmapFilterQuality &&
runtimeType == other.runtimeType &&
bitmapSampling == other.bitmapSampling &&
mipmapSampling == other.mipmapSampling;

@override
int get hashCode => bitmapSampling.hashCode ^ mipmapSampling.hashCode;
}

class _CubicFilterQuality implements FilterQuality {
const _CubicFilterQuality();

@override
int get _nativeIndex {
assert(_filterQualitiesFromNative[6] == this);
return 6;
}

@override
bool operator ==(Object other) =>
identical(this, other) || other is _CubicFilterQuality && runtimeType == other.runtimeType;

@override
int get hashCode => 0;
high,
}

/// Styles to use for line endings.
Expand Down Expand Up @@ -1507,11 +1386,11 @@ class Paint {
/// Defaults to [FilterQuality.none].
// TODO(ianh): verify that the image drawing methods actually respect this
FilterQuality get filterQuality {
return _filterQualitiesFromNative[_data.getInt32(_kFilterQualityOffset, _kFakeHostEndian)];
return FilterQuality.values[_data.getInt32(_kFilterQualityOffset, _kFakeHostEndian)];
}
set filterQuality(FilterQuality value) {
assert(value != null); // ignore: unnecessary_null_comparison
final int encoded = value._nativeIndex;
final int encoded = value.index;
_data.setInt32(_kFilterQualityOffset, encoded, _kFakeHostEndian);
}

Expand Down Expand Up @@ -3475,7 +3354,7 @@ class _ImageFilter extends NativeFieldWrapperClass2 {
if (filter.data.length != 16)
throw ArgumentError('"matrix4" must have 16 entries.');
_constructor();
_initMatrix(filter.data, filter.filterQuality._nativeIndex);
_initMatrix(filter.data, filter.filterQuality.index);
}
void _initMatrix(Float64List matrix4, int filterQuality) native 'ImageFilter_initMatrix';

Expand Down Expand Up @@ -3830,7 +3709,7 @@ class ImageShader extends Shader {
if (matrix4.length != 16)
throw ArgumentError('"matrix4" must have 16 entries.');
_constructor();
_initWithImage(image._image, tmx.index, tmy.index, filterQuality?._nativeIndex ?? -1, matrix4);
_initWithImage(image._image, tmx.index, tmy.index, filterQuality?.index ?? -1, matrix4);
}
void _constructor() native 'ImageShader_constructor';
void _initWithImage(_Image image, int tmx, int tmy, int filterQualityIndex, Float64List matrix4) native 'ImageShader_initWithImage';
Expand Down Expand Up @@ -4434,7 +4313,7 @@ class Canvas extends NativeFieldWrapperClass2 {
assert(image != null); // image is checked on the engine side
assert(_offsetIsValid(offset));
assert(paint != null); // ignore: unnecessary_null_comparison
_drawImage(image._image, offset.dx, offset.dy, paint._objects, paint._data, paint.filterQuality._nativeIndex);
_drawImage(image._image, offset.dx, offset.dy, paint._objects, paint._data, paint.filterQuality.index);
}
void _drawImage(_Image image,
double x,
Expand Down Expand Up @@ -4469,7 +4348,7 @@ class Canvas extends NativeFieldWrapperClass2 {
dst.bottom,
paint._objects,
paint._data,
paint.filterQuality._nativeIndex);
paint.filterQuality.index);
}
void _drawImageRect(_Image image,
double srcLeft,
Expand Down Expand Up @@ -4503,10 +4382,6 @@ class Canvas extends NativeFieldWrapperClass2 {
assert(_rectIsValid(center));
assert(_rectIsValid(dst));
assert(paint != null); // ignore: unnecessary_null_comparison
final BitmapFilterSampling sampling = (paint.filterQuality is _MipmapFilterQuality)
? (paint.filterQuality as _MipmapFilterQuality).bitmapSampling
: BitmapFilterSampling.bilinear;
// TODO: add filtering to public API, since native paint's quality is deprecated
_drawImageNine(image._image,
center.left,
center.top,
Expand All @@ -4518,7 +4393,7 @@ class Canvas extends NativeFieldWrapperClass2 {
dst.bottom,
paint._objects,
paint._data,
sampling.index);
paint.filterQuality.index);
}
void _drawImageNine(_Image image,
double centerLeft,
Expand All @@ -4531,7 +4406,7 @@ class Canvas extends NativeFieldWrapperClass2 {
double dstBottom,
List<dynamic>? paintObjects,
ByteData paintData,
int bitmapSamplingIndex) native 'Canvas_drawImageNine';
int filterQualityIndex) native 'Canvas_drawImageNine';

/// Draw the given picture onto the canvas. To create a picture, see
/// [PictureRecorder].
Expand Down Expand Up @@ -4796,7 +4671,7 @@ class Canvas extends NativeFieldWrapperClass2 {

final Int32List? colorBuffer = (colors == null || colors.isEmpty) ? null : _encodeColorList(colors);
final Float32List? cullRectBuffer = cullRect?._value32;
final int qualityIndex = paint.filterQuality._nativeIndex;
final int qualityIndex = paint.filterQuality.index;

_drawAtlas(
paint._objects, paint._data, qualityIndex, atlas._image, rstTransformBuffer, rectBuffer,
Expand Down Expand Up @@ -4966,7 +4841,7 @@ class Canvas extends NativeFieldWrapperClass2 {
throw ArgumentError('"rstTransforms" and "rects" lengths must be a multiple of four.');
if (colors != null && colors.length * 4 != rectCount)
throw ArgumentError('If non-null, "colors" length must be one fourth the length of "rstTransforms" and "rects".');
final int qualityIndex = paint.filterQuality._nativeIndex;
final int qualityIndex = paint.filterQuality.index;

_drawAtlas(
paint._objects, paint._data, qualityIndex, atlas._image, rstTransforms, rects,
Expand Down
11 changes: 4 additions & 7 deletions lib/ui/painting/canvas.cc
View file
Expand Up @@ -326,8 +326,7 @@ void Canvas::drawImage(const CanvasImage* image,
ToDart("Canvas.drawImage called with non-genuine Image."));
return;
}
SkSamplingOptions sampling =
ImageFilter::fromFilterQualityIndex(filterQualityIndex);
auto sampling = ImageFilter::SamplingFromIndex(filterQualityIndex);
canvas_->drawImage(image->image(), x, y, sampling, paint.paint());
}

Expand All @@ -353,8 +352,7 @@ void Canvas::drawImageRect(const CanvasImage* image,
}
SkRect src = SkRect::MakeLTRB(src_left, src_top, src_right, src_bottom);
SkRect dst = SkRect::MakeLTRB(dst_left, dst_top, dst_right, dst_bottom);
SkSamplingOptions sampling =
ImageFilter::fromFilterQualityIndex(filterQualityIndex);
auto sampling = ImageFilter::SamplingFromIndex(filterQualityIndex);
canvas_->drawImageRect(image->image(), src, dst, sampling, paint.paint(),
SkCanvas::kFast_SrcRectConstraint);
}
Expand Down Expand Up @@ -384,7 +382,7 @@ void Canvas::drawImageNine(const CanvasImage* image,
SkIRect icenter;
center.round(&icenter);
SkRect dst = SkRect::MakeLTRB(dst_left, dst_top, dst_right, dst_bottom);
SkFilterMode filter = static_cast<SkFilterMode>(bitmapSamplingIndex);
auto filter = ImageFilter::FilterModeFromIndex(bitmapSamplingIndex);
canvas_->drawImageNine(image->image().get(), icenter, dst, filter,
paint.paint());
}
Expand Down Expand Up @@ -459,8 +457,7 @@ void Canvas::drawAtlas(const Paint& paint,
static_assert(sizeof(SkRect) == sizeof(float) * 4,
"SkRect doesn't use floats.");

SkSamplingOptions sampling =
ImageFilter::fromFilterQualityIndex(filterQualityIndex);
auto sampling = ImageFilter::SamplingFromIndex(filterQualityIndex);

canvas_->drawAtlas(
skImage.get(), reinterpret_cast<const SkRSXform*>(transforms.data()),
Expand Down

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