flutter_flutter/packages/flutter/lib/src/rendering/image.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:ui' as ui show Image;

import 'package:flutter/animation.dart';

import 'box.dart';
import 'object.dart';

export 'package:flutter/painting.dart' show
  BoxFit,
  ImageRepeat;

/// An image in the render tree.
///
/// The render image attempts to find a size for itself that fits in the given
/// constraints and preserves the image's intrinsic aspect ratio.
///
/// The image is painted using [paintImage], which describes the meanings of the
/// various fields on this class in more detail.
class RenderImage extends RenderBox {
  /// Creates a render box that displays an image.
  ///
  /// The [scale], [alignment], [repeat], [matchTextDirection] and [filterQuality] arguments
  /// must not be null. The [textDirection] argument must not be null if
  /// [alignment] will need resolving or if [matchTextDirection] is true.
  RenderImage({
    ui.Image? image,
    this.debugImageLabel,
    double? width,
    double? height,
    double scale = 1.0,
    Color? color,
    Animation<double>? opacity,
    BlendMode? colorBlendMode,
    BoxFit? fit,
    AlignmentGeometry alignment = Alignment.center,
    ImageRepeat repeat = ImageRepeat.noRepeat,
    Rect? centerSlice,
    bool matchTextDirection = false,
    TextDirection? textDirection,
    bool invertColors = false,
    bool isAntiAlias = false,
    FilterQuality filterQuality = FilterQuality.low,
  }) : assert(scale != null),
       assert(repeat != null),
       assert(alignment != null),
       assert(filterQuality != null),
       assert(matchTextDirection != null),
       assert(isAntiAlias != null),
       _image = image,
       _width = width,
       _height = height,
       _scale = scale,
       _color = color,
       _opacity = opacity,
       _colorBlendMode = colorBlendMode,
       _fit = fit,
       _alignment = alignment,
       _repeat = repeat,
       _centerSlice = centerSlice,
       _matchTextDirection = matchTextDirection,
       _invertColors = invertColors,
       _textDirection = textDirection,
       _isAntiAlias = isAntiAlias,
       _filterQuality = filterQuality {
    _updateColorFilter();
  }

  Alignment? _resolvedAlignment;
  bool? _flipHorizontally;

  void _resolve() {
    if (_resolvedAlignment != null) {
      return;
    }
    _resolvedAlignment = alignment.resolve(textDirection);
    _flipHorizontally = matchTextDirection && textDirection == TextDirection.rtl;
  }

  void _markNeedResolution() {
    _resolvedAlignment = null;
    _flipHorizontally = null;
    markNeedsPaint();
  }

  /// The image to display.
  ui.Image? get image => _image;
  ui.Image? _image;
  set image(ui.Image? value) {
    if (value == _image) {
      return;
    }
    // If we get a clone of our image, it's the same underlying native data -
    // dispose of the new clone and return early.
    if (value != null && _image != null && value.isCloneOf(_image!)) {
      value.dispose();
      return;
    }
    _image?.dispose();
    _image = value;
    markNeedsPaint();
    if (_width == null || _height == null) {
      markNeedsLayout();
    }
  }

  /// A string used to identify the source of the image.
  String? debugImageLabel;

  /// If non-null, requires the image to have this width.
  ///
  /// If null, the image will pick a size that best preserves its intrinsic
  /// aspect ratio.
  double? get width => _width;
  double? _width;
  set width(double? value) {
    if (value == _width) {
      return;
    }
    _width = value;
    markNeedsLayout();
  }

  /// If non-null, require the image to have this height.
  ///
  /// If null, the image will pick a size that best preserves its intrinsic
  /// aspect ratio.
  double? get height => _height;
  double? _height;
  set height(double? value) {
    if (value == _height) {
      return;
    }
    _height = value;
    markNeedsLayout();
  }

  /// Specifies the image's scale.
  ///
  /// Used when determining the best display size for the image.
  double get scale => _scale;
  double _scale;
  set scale(double value) {
    assert(value != null);
    if (value == _scale) {
      return;
    }
    _scale = value;
    markNeedsLayout();
  }

  ColorFilter? _colorFilter;

  void _updateColorFilter() {
    if (_color == null) {
      _colorFilter = null;
    } else {
      _colorFilter = ColorFilter.mode(_color!, _colorBlendMode ?? BlendMode.srcIn);
    }
  }

  /// If non-null, this color is blended with each image pixel using [colorBlendMode].
  Color? get color => _color;
  Color? _color;
  set color(Color? value) {
    if (value == _color) {
      return;
    }
    _color = value;
    _updateColorFilter();
    markNeedsPaint();
  }

  /// If non-null, the value from the [Animation] is multiplied with the opacity
  /// of each image pixel before painting onto the canvas.
  Animation<double>? get opacity => _opacity;
  Animation<double>? _opacity;
  set opacity(Animation<double>? value) {
    if (value == _opacity) {
      return;
    }

    if (attached) {
      _opacity?.removeListener(markNeedsPaint);
    }
    _opacity = value;
    if (attached) {
      value?.addListener(markNeedsPaint);
    }
  }

  /// Used to set the filterQuality of the image.
  ///
  /// Use the [FilterQuality.low] quality setting to scale the image, which corresponds to
  /// bilinear interpolation, rather than the default [FilterQuality.none] which corresponds
  /// to nearest-neighbor.
  FilterQuality get filterQuality => _filterQuality;
  FilterQuality _filterQuality;
  set filterQuality(FilterQuality value) {
    assert(value != null);
    if (value == _filterQuality) {
      return;
    }
    _filterQuality = value;
    markNeedsPaint();
  }


  /// Used to combine [color] with this image.
  ///
  /// The default is [BlendMode.srcIn]. In terms of the blend mode, [color] is
  /// the source and this image is the destination.
  ///
  /// See also:
  ///
  ///  * [BlendMode], which includes an illustration of the effect of each blend mode.
  BlendMode? get colorBlendMode => _colorBlendMode;
  BlendMode? _colorBlendMode;
  set colorBlendMode(BlendMode? value) {
    if (value == _colorBlendMode) {
      return;
    }
    _colorBlendMode = value;
    _updateColorFilter();
    markNeedsPaint();
  }

  /// How to inscribe the image into the space allocated during layout.
  ///
  /// The default varies based on the other fields. See the discussion at
  /// [paintImage].
  BoxFit? get fit => _fit;
  BoxFit? _fit;
  set fit(BoxFit? value) {
    if (value == _fit) {
      return;
    }
    _fit = value;
    markNeedsPaint();
  }

  /// How to align the image within its bounds.
  ///
  /// If this is set to a text-direction-dependent value, [textDirection] must
  /// not be null.
  AlignmentGeometry get alignment => _alignment;
  AlignmentGeometry _alignment;
  set alignment(AlignmentGeometry value) {
    assert(value != null);
    if (value == _alignment) {
      return;
    }
    _alignment = value;
    _markNeedResolution();
  }

  /// How to repeat this image if it doesn't fill its layout bounds.
  ImageRepeat get repeat => _repeat;
  ImageRepeat _repeat;
  set repeat(ImageRepeat value) {
    assert(value != null);
    if (value == _repeat) {
      return;
    }
    _repeat = value;
    markNeedsPaint();
  }

  /// The center slice for a nine-patch image.
  ///
  /// The region of the image inside the center slice will be stretched both
  /// horizontally and vertically to fit the image into its destination. The
  /// region of the image above and below the center slice will be stretched
  /// only horizontally and the region of the image to the left and right of
  /// the center slice will be stretched only vertically.
  Rect? get centerSlice => _centerSlice;
  Rect? _centerSlice;
  set centerSlice(Rect? value) {
    if (value == _centerSlice) {
      return;
    }
    _centerSlice = value;
    markNeedsPaint();
  }

  /// Whether to invert the colors of the image.
  ///
  /// Inverting the colors of an image applies a new color filter to the paint.
  /// If there is another specified color filter, the invert will be applied
  /// after it. This is primarily used for implementing smart invert on iOS.
  bool get invertColors => _invertColors;
  bool _invertColors;
  set invertColors(bool value) {
    if (value == _invertColors) {
      return;
    }
    _invertColors = value;
    markNeedsPaint();
  }

  /// Whether to paint the image in the direction of the [TextDirection].
  ///
  /// If this is true, then in [TextDirection.ltr] contexts, the image will be
  /// drawn with its origin in the top left (the "normal" painting direction for
  /// images); and in [TextDirection.rtl] contexts, the image will be drawn with
  /// a scaling factor of -1 in the horizontal direction so that the origin is
  /// in the top right.
  ///
  /// This is occasionally used with images in right-to-left environments, for
  /// images that were designed for left-to-right locales. Be careful, when
  /// using this, to not flip images with integral shadows, text, or other
  /// effects that will look incorrect when flipped.
  ///
  /// If this is set to true, [textDirection] must not be null.
  bool get matchTextDirection => _matchTextDirection;
  bool _matchTextDirection;
  set matchTextDirection(bool value) {
    assert(value != null);
    if (value == _matchTextDirection) {
      return;
    }
    _matchTextDirection = value;
    _markNeedResolution();
  }

  /// The text direction with which to resolve [alignment].
  ///
  /// This may be changed to null, but only after the [alignment] and
  /// [matchTextDirection] properties have been changed to values that do not
  /// depend on the direction.
  TextDirection? get textDirection => _textDirection;
  TextDirection? _textDirection;
  set textDirection(TextDirection? value) {
    if (_textDirection == value) {
      return;
    }
    _textDirection = value;
    _markNeedResolution();
  }

  /// Whether to paint the image with anti-aliasing.
  ///
  /// Anti-aliasing alleviates the sawtooth artifact when the image is rotated.
  bool get isAntiAlias => _isAntiAlias;
  bool _isAntiAlias;
  set isAntiAlias(bool value) {
    if (_isAntiAlias == value) {
      return;
    }
    assert(value != null);
    _isAntiAlias = value;
    markNeedsPaint();
  }

  /// Find a size for the render image within the given constraints.
  ///
  ///  - The dimensions of the RenderImage must fit within the constraints.
  ///  - The aspect ratio of the RenderImage matches the intrinsic aspect
  ///    ratio of the image.
  ///  - The RenderImage's dimension are maximal subject to being smaller than
  ///    the intrinsic size of the image.
  Size _sizeForConstraints(BoxConstraints constraints) {
    // Folds the given |width| and |height| into |constraints| so they can all
    // be treated uniformly.
    constraints = BoxConstraints.tightFor(
      width: _width,
      height: _height,
    ).enforce(constraints);

    if (_image == null) {
      return constraints.smallest;
    }

    return constraints.constrainSizeAndAttemptToPreserveAspectRatio(Size(
      _image!.width.toDouble() / _scale,
      _image!.height.toDouble() / _scale,
    ));
  }

  @override
  double computeMinIntrinsicWidth(double height) {
    assert(height >= 0.0);
    if (_width == null && _height == null) {
      return 0.0;
    }
    return _sizeForConstraints(BoxConstraints.tightForFinite(height: height)).width;
  }

  @override
  double computeMaxIntrinsicWidth(double height) {
    assert(height >= 0.0);
    return _sizeForConstraints(BoxConstraints.tightForFinite(height: height)).width;
  }

  @override
  double computeMinIntrinsicHeight(double width) {
    assert(width >= 0.0);
    if (_width == null && _height == null) {
      return 0.0;
    }
    return _sizeForConstraints(BoxConstraints.tightForFinite(width: width)).height;
  }

  @override
  double computeMaxIntrinsicHeight(double width) {
    assert(width >= 0.0);
    return _sizeForConstraints(BoxConstraints.tightForFinite(width: width)).height;
  }

  @override
  bool hitTestSelf(Offset position) => true;

  @override
  Size computeDryLayout(BoxConstraints constraints) {
    return _sizeForConstraints(constraints);
  }

  @override
  void performLayout() {
    size = _sizeForConstraints(constraints);
  }

  @override
  void attach(covariant PipelineOwner owner) {
    super.attach(owner);
    _opacity?.addListener(markNeedsPaint);
  }

  @override
  void detach() {
    _opacity?.removeListener(markNeedsPaint);
    super.detach();
  }

  @override
  void paint(PaintingContext context, Offset offset) {
    if (_image == null) {
      return;
    }
    _resolve();
    assert(_resolvedAlignment != null);
    assert(_flipHorizontally != null);
    paintImage(
      canvas: context.canvas,
      rect: offset & size,
      image: _image!,
      debugImageLabel: debugImageLabel,
      scale: _scale,
      opacity: _opacity?.value ?? 1.0,
      colorFilter: _colorFilter,
      fit: _fit,
      alignment: _resolvedAlignment!,
      centerSlice: _centerSlice,
      repeat: _repeat,
      flipHorizontally: _flipHorizontally!,
      invertColors: invertColors,
      filterQuality: _filterQuality,
      isAntiAlias: _isAntiAlias,
    );
  }

  @override
  void dispose() {
    _image?.dispose();
    _image = null;
    super.dispose();
  }

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    properties.add(DiagnosticsProperty<ui.Image>('image', image));
    properties.add(DoubleProperty('width', width, defaultValue: null));
    properties.add(DoubleProperty('height', height, defaultValue: null));
    properties.add(DoubleProperty('scale', scale, defaultValue: 1.0));
    properties.add(ColorProperty('color', color, defaultValue: null));
    properties.add(DiagnosticsProperty<Animation<double>?>('opacity', opacity, defaultValue: null));
    properties.add(EnumProperty<BlendMode>('colorBlendMode', colorBlendMode, defaultValue: null));
    properties.add(EnumProperty<BoxFit>('fit', fit, defaultValue: null));
    properties.add(DiagnosticsProperty<AlignmentGeometry>('alignment', alignment, defaultValue: null));
    properties.add(EnumProperty<ImageRepeat>('repeat', repeat, defaultValue: ImageRepeat.noRepeat));
    properties.add(DiagnosticsProperty<Rect>('centerSlice', centerSlice, defaultValue: null));
    properties.add(FlagProperty('matchTextDirection', value: matchTextDirection, ifTrue: 'match text direction'));
    properties.add(EnumProperty<TextDirection>('textDirection', textDirection, defaultValue: null));
    properties.add(DiagnosticsProperty<bool>('invertColors', invertColors));
    properties.add(EnumProperty<FilterQuality>('filterQuality', filterQuality));
  }
}