decoration_image.dart 23.6 KB
Newer Older
Ian Hickson's avatar
Ian Hickson committed
1
// Copyright 2014 The Flutter Authors. All rights reserved.
2 3 4
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

5

6
import 'dart:developer' as developer;
7 8 9
import 'dart:ui' as ui show Image;

import 'package:flutter/foundation.dart';
10
import 'package:flutter/scheduler.dart';
11

12
import 'alignment.dart';
13
import 'basic_types.dart';
14
import 'borders.dart';
15
import 'box_fit.dart';
16
import 'debug.dart';
17 18
import 'image_provider.dart';
import 'image_stream.dart';
19 20 21 22 23 24 25 26 27 28 29 30

/// How to paint any portions of a box not covered by an image.
enum ImageRepeat {
  /// Repeat the image in both the x and y directions until the box is filled.
  repeat,

  /// Repeat the image in the x direction until the box is filled horizontally.
  repeatX,

  /// Repeat the image in the y direction until the box is filled vertically.
  repeatY,

31
  /// Leave uncovered portions of the box transparent.
32
  noRepeat,
33 34 35 36 37 38 39 40 41 42
}

/// An image for a box decoration.
///
/// The image is painted using [paintImage], which describes the meanings of the
/// various fields on this class in more detail.
@immutable
class DecorationImage {
  /// Creates an image to show in a [BoxDecoration].
  ///
Ian Hickson's avatar
Ian Hickson committed
43 44
  /// The [image], [alignment], [repeat], and [matchTextDirection] arguments
  /// must not be null.
45
  const DecorationImage({
46
    required this.image,
47
    this.onError,
48 49
    this.colorFilter,
    this.fit,
50
    this.alignment = Alignment.center,
51
    this.centerSlice,
52 53
    this.repeat = ImageRepeat.noRepeat,
    this.matchTextDirection = false,
54
    this.scale = 1.0,
Ian Hickson's avatar
Ian Hickson committed
55 56 57
  }) : assert(image != null),
       assert(alignment != null),
       assert(repeat != null),
58 59
       assert(matchTextDirection != null),
       assert(scale != null);
60 61 62 63 64 65 66

  /// The image to be painted into the decoration.
  ///
  /// Typically this will be an [AssetImage] (for an image shipped with the
  /// application) or a [NetworkImage] (for an image obtained from the network).
  final ImageProvider image;

67
  /// An optional error callback for errors emitted when loading [image].
68
  final ImageErrorListener? onError;
69

70
  /// A color filter to apply to the image before painting it.
71
  final ColorFilter? colorFilter;
72 73 74 75 76 77 78

  /// How the image should be inscribed into the box.
  ///
  /// The default is [BoxFit.scaleDown] if [centerSlice] is null, and
  /// [BoxFit.fill] if [centerSlice] is not null.
  ///
  /// See the discussion at [paintImage] for more details.
79
  final BoxFit? fit;
80 81 82

  /// How to align the image within its bounds.
  ///
Ian Hickson's avatar
Ian Hickson committed
83
  /// The alignment aligns the given position in the image to the given position
84
  /// in the layout bounds. For example, an [Alignment] alignment of (-1.0,
85 86
  /// -1.0) aligns the image to the top-left corner of its layout bounds, while a
  /// [Alignment] alignment of (1.0, 1.0) aligns the bottom right of the
Ian Hickson's avatar
Ian Hickson committed
87
  /// image with the bottom right corner of its layout bounds. Similarly, an
88
  /// alignment of (0.0, 1.0) aligns the bottom middle of the image with the
Ian Hickson's avatar
Ian Hickson committed
89 90 91 92 93 94
  /// middle of the bottom edge of its layout bounds.
  ///
  /// To display a subpart of an image, consider using a [CustomPainter] and
  /// [Canvas.drawImageRect].
  ///
  /// If the [alignment] is [TextDirection]-dependent (i.e. if it is a
95
  /// [AlignmentDirectional]), then a [TextDirection] must be available
Ian Hickson's avatar
Ian Hickson committed
96
  /// when the image is painted.
97
  ///
98
  /// Defaults to [Alignment.center].
99 100 101 102 103 104 105
  ///
  /// See also:
  ///
  ///  * [Alignment], a class with convenient constants typically used to
  ///    specify an [AlignmentGeometry].
  ///  * [AlignmentDirectional], like [Alignment] for specifying alignments
  ///    relative to text direction.
106
  final AlignmentGeometry alignment;
107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122

  /// 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.
  ///
  /// The stretching will be applied in order to make the image fit into the box
  /// specified by [fit]. When [centerSlice] is not null, [fit] defaults to
  /// [BoxFit.fill], which distorts the destination image size relative to the
  /// image's original aspect ratio. Values of [BoxFit] which do not distort the
  /// destination image size will result in [centerSlice] having no effect
  /// (since the nine regions of the image will be rendered with the same
  /// scaling, as if it wasn't specified).
123
  final Rect? centerSlice;
124 125 126 127 128

  /// How to paint any portions of the box that would not otherwise be covered
  /// by the image.
  final ImageRepeat repeat;

Ian Hickson's avatar
Ian Hickson committed
129 130 131 132 133 134 135 136 137
  /// 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.
  final bool matchTextDirection;

138 139
  /// Defines image pixels to be shown per logical pixels.
  ///
140
  /// By default the value of scale is 1.0. The scale for the image is
141 142 143
  /// calculated by multiplying [scale] with `scale` of the given [ImageProvider].
  final double scale;

144 145 146 147 148 149 150
  /// Creates a [DecorationImagePainter] for this [DecorationImage].
  ///
  /// The `onChanged` argument must not be null. It will be called whenever the
  /// image needs to be repainted, e.g. because it is loading incrementally or
  /// because it is animated.
  DecorationImagePainter createPainter(VoidCallback onChanged) {
    assert(onChanged != null);
151
    return DecorationImagePainter._(this, onChanged);
152 153
  }

154
  @override
155
  bool operator ==(Object other) {
156 157
    if (identical(this, other))
      return true;
158
    if (other.runtimeType != runtimeType)
159
      return false;
160 161 162 163 164 165 166
    return other is DecorationImage
        && other.image == image
        && other.colorFilter == colorFilter
        && other.fit == fit
        && other.alignment == alignment
        && other.centerSlice == centerSlice
        && other.repeat == repeat
167 168
        && other.matchTextDirection == matchTextDirection
        && other.scale == scale;
169 170 171
  }

  @override
172
  int get hashCode => hashValues(image, colorFilter, fit, alignment, centerSlice, repeat, matchTextDirection, scale);
173 174 175

  @override
  String toString() {
176 177 178 179 180 181 182 183 184 185 186 187 188 189 190
    final List<String> properties = <String>[
      '$image',
      if (colorFilter != null)
        '$colorFilter',
      if (fit != null &&
          !(fit == BoxFit.fill && centerSlice != null) &&
          !(fit == BoxFit.scaleDown && centerSlice == null))
        '$fit',
      '$alignment',
      if (centerSlice != null)
        'centerSlice: $centerSlice',
      if (repeat != ImageRepeat.noRepeat)
        '$repeat',
      if (matchTextDirection)
        'match text direction',
191
      'scale: $scale',
192
    ];
193
    return '${objectRuntimeType(this, 'DecorationImage')}(${properties.join(", ")})';
194 195 196
  }
}

197 198 199 200 201 202 203 204 205 206 207 208
/// The painter for a [DecorationImage].
///
/// To obtain a painter, call [DecorationImage.createPainter].
///
/// To paint, call [paint]. The `onChanged` callback passed to
/// [DecorationImage.createPainter] will be called if the image needs to paint
/// again (e.g. because it is animated or because it had not yet loaded the
/// first time the [paint] method was called).
///
/// This object should be disposed using the [dispose] method when it is no
/// longer needed.
class DecorationImagePainter {
209
  DecorationImagePainter._(this._details, this._onChanged) : assert(_details != null);
210 211 212 213

  final DecorationImage _details;
  final VoidCallback _onChanged;

214 215
  ImageStream? _imageStream;
  ImageInfo? _image;
216

217 218 219 220 221 222 223 224 225 226 227 228 229 230
  /// Draw the image onto the given canvas.
  ///
  /// The image is drawn at the position and size given by the `rect` argument.
  ///
  /// The image is clipped to the given `clipPath`, if any.
  ///
  /// The `configuration` object is used to resolve the image (e.g. to pick
  /// resolution-specific assets), and to implement the
  /// [DecorationImage.matchTextDirection] feature.
  ///
  /// If the image needs to be painted again, e.g. because it is animated or
  /// because it had not yet been loaded the first time this method was called,
  /// then the `onChanged` callback passed to [DecorationImage.createPainter]
  /// will be called.
231
  void paint(Canvas canvas, Rect rect, Path? clipPath, ImageConfiguration configuration) {
232 233 234 235 236 237 238 239 240 241
    assert(canvas != null);
    assert(rect != null);
    assert(configuration != null);

    bool flipHorizontally = false;
    if (_details.matchTextDirection) {
      assert(() {
        // We check this first so that the assert will fire immediately, not just
        // when the image is ready.
        if (configuration.textDirection == null) {
242
          throw FlutterError.fromParts(<DiagnosticsNode>[
243
            ErrorSummary('DecorationImage.matchTextDirection can only be used when a TextDirection is available.'),
244 245
            ErrorDescription(
              'When DecorationImagePainter.paint() was called, there was no text direction provided '
246
              'in the ImageConfiguration object to match.',
247 248 249 250
            ),
            DiagnosticsProperty<DecorationImage>('The DecorationImage was', _details, style: DiagnosticsTreeStyle.errorProperty),
            DiagnosticsProperty<ImageConfiguration>('The ImageConfiguration was', configuration, style: DiagnosticsTreeStyle.errorProperty),
          ]);
251 252 253 254 255 256 257 258 259
        }
        return true;
      }());
      if (configuration.textDirection == TextDirection.rtl)
        flipHorizontally = true;
    }

    final ImageStream newImageStream = _details.image.resolve(configuration);
    if (newImageStream.key != _imageStream?.key) {
260 261 262 263
      final ImageStreamListener listener = ImageStreamListener(
        _handleImage,
        onError: _details.onError,
      );
264
      _imageStream?.removeListener(listener);
265
      _imageStream = newImageStream;
266
      _imageStream!.addListener(listener);
267 268 269 270 271 272 273 274 275 276 277 278
    }
    if (_image == null)
      return;

    if (clipPath != null) {
      canvas.save();
      canvas.clipPath(clipPath);
    }

    paintImage(
      canvas: canvas,
      rect: rect,
279 280 281
      image: _image!.image,
      debugImageLabel: _image!.debugLabel,
      scale: _details.scale * _image!.scale,
282 283 284 285 286 287
      colorFilter: _details.colorFilter,
      fit: _details.fit,
      alignment: _details.alignment.resolve(configuration.textDirection),
      centerSlice: _details.centerSlice,
      repeat: _details.repeat,
      flipHorizontally: flipHorizontally,
288
      filterQuality: FilterQuality.low,
289 290 291 292 293 294
    );

    if (clipPath != null)
      canvas.restore();
  }

295
  void _handleImage(ImageInfo value, bool synchronousCall) {
296 297
    if (_image == value)
      return;
298 299 300 301 302
    if (_image != null && _image!.isCloneOf(value)) {
      value.dispose();
      return;
    }
    _image?.dispose();
303 304 305 306 307 308 309 310 311 312 313 314 315
    _image = value;
    assert(_onChanged != null);
    if (!synchronousCall)
      _onChanged();
  }

  /// Releases the resources used by this painter.
  ///
  /// This should be called whenever the painter is no longer needed.
  ///
  /// After this method has been called, the object is no longer usable.
  @mustCallSuper
  void dispose() {
316 317 318 319
    _imageStream?.removeListener(ImageStreamListener(
      _handleImage,
      onError: _details.onError,
    ));
320 321
    _image?.dispose();
    _image = null;
322
  }
323 324 325

  @override
  String toString() {
326
    return '${objectRuntimeType(this, 'DecorationImagePainter')}(stream: $_imageStream, image: $_image) for $_details';
327
  }
328 329
}

330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348
/// Used by [paintImage] to report image sizes drawn at the end of the frame.
Map<String, ImageSizeInfo> _pendingImageSizeInfo = <String, ImageSizeInfo>{};

/// [ImageSizeInfo]s that were reported on the last frame.
///
/// Used to prevent duplicative reports from frame to frame.
Set<ImageSizeInfo> _lastFrameImageSizeInfo = <ImageSizeInfo>{};

/// Flushes inter-frame tracking of image size information from [paintImage].
///
/// Has no effect if asserts are disabled.
@visibleForTesting
void debugFlushLastFrameImageSizeInfo() {
  assert(() {
    _lastFrameImageSizeInfo = <ImageSizeInfo>{};
    return true;
  }());
}

349 350
/// Paints an image into the given rectangle on the canvas.
///
Ian Hickson's avatar
Ian Hickson committed
351 352
/// The arguments have the following meanings:
///
353
///  * `canvas`: The canvas onto which the image will be painted.
Ian Hickson's avatar
Ian Hickson committed
354
///
355 356 357
///  * `rect`: The region of the canvas into which the image will be painted.
///    The image might not fill the entire rectangle (e.g., depending on the
///    `fit`). If `rect` is empty, nothing is painted.
Ian Hickson's avatar
Ian Hickson committed
358
///
359
///  * `image`: The image to paint onto the canvas.
Ian Hickson's avatar
Ian Hickson committed
360
///
361 362
///  * `scale`: The number of image pixels for each logical pixel.
///
363 364
///  * `colorFilter`: If non-null, the color filter to apply when painting the
///    image.
Ian Hickson's avatar
Ian Hickson committed
365
///
366 367 368 369 370
///  * `fit`: How the image should be inscribed into `rect`. If null, the
///    default behavior depends on `centerSlice`. If `centerSlice` is also null,
///    the default behavior is [BoxFit.scaleDown]. If `centerSlice` is
///    non-null, the default behavior is [BoxFit.fill]. See [BoxFit] for
///    details.
Ian Hickson's avatar
Ian Hickson committed
371 372 373
///
///  * `alignment`: How the destination rectangle defined by applying `fit` is
///    aligned within `rect`. For example, if `fit` is [BoxFit.contain] and
374
///    `alignment` is [Alignment.bottomRight], the image will be as large
Ian Hickson's avatar
Ian Hickson committed
375
///    as possible within `rect` and placed with its bottom right corner at the
376
///    bottom right corner of `rect`. Defaults to [Alignment.center].
Ian Hickson's avatar
Ian Hickson committed
377
///
378 379 380 381 382 383 384 385 386 387
///  * `centerSlice`: The image is drawn in nine portions described by splitting
///    the image by drawing two horizontal lines and two vertical lines, where
///    `centerSlice` describes the rectangle formed by the four points where
///    these four lines intersect each other. (This forms a 3-by-3 grid
///    of regions, the center region being described by `centerSlice`.)
///    The four regions in the corners are drawn, without scaling, in the four
///    corners of the destination rectangle defined by applying `fit`. The
///    remaining five regions are drawn by stretching them to fit such that they
///    exactly cover the destination rectangle while maintaining their relative
///    positions.
Ian Hickson's avatar
Ian Hickson committed
388 389 390 391 392 393 394 395 396 397 398
///
///  * `repeat`: If the image does not fill `rect`, whether and how the image
///    should be repeated to fill `rect`. By default, the image is not repeated.
///    See [ImageRepeat] for details.
///
///  * `flipHorizontally`: Whether to flip the image horizontally. This is
///    occasionally used with images in right-to-left environments, for images
///    that were designed for left-to-right locales (or vice versa). Be careful,
///    when using this, to not flip images with integral shadows, text, or other
///    effects that will look incorrect when flipped.
///
399 400 401 402 403
///  * `invertColors`: 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.
///
404 405 406 407 408 409
///  * `filterQuality`: Use this to change the quality when scaling an 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.
///
/// The `canvas`, `rect`, `image`, `scale`, `alignment`, `repeat`, `flipHorizontally` and `filterQuality`
Ian Hickson's avatar
Ian Hickson committed
410
/// arguments must not be null.
411 412 413 414 415 416 417
///
/// See also:
///
///  * [paintBorder], which paints a border around a rectangle on a canvas.
///  * [DecorationImage], which holds a configuration for calling this function.
///  * [BoxDecoration], which uses this function to paint a [DecorationImage].
void paintImage({
418 419 420 421
  required Canvas canvas,
  required Rect rect,
  required ui.Image image,
  String? debugImageLabel,
422
  double scale = 1.0,
423 424
  ColorFilter? colorFilter,
  BoxFit? fit,
425
  Alignment alignment = Alignment.center,
426
  Rect? centerSlice,
427 428
  ImageRepeat repeat = ImageRepeat.noRepeat,
  bool flipHorizontally = false,
429
  bool invertColors = false,
430
  FilterQuality filterQuality = FilterQuality.low,
431
  bool isAntiAlias = false,
432 433 434
}) {
  assert(canvas != null);
  assert(image != null);
Ian Hickson's avatar
Ian Hickson committed
435 436 437
  assert(alignment != null);
  assert(repeat != null);
  assert(flipHorizontally != null);
438
  assert(isAntiAlias != null);
439 440 441 442
  assert(
    image.debugGetOpenHandleStackTraces()?.isNotEmpty ?? true,
    'Cannot paint an image that is disposed.\n'
    'The caller of paintImage is expected to wait to dispose the image until '
443
    'after painting has completed.',
444
  );
445 446 447
  if (rect.isEmpty)
    return;
  Size outputSize = rect.size;
448
  Size inputSize = Size(image.width.toDouble(), image.height.toDouble());
449
  Offset? sliceBorder;
450
  if (centerSlice != null) {
451
    sliceBorder = inputSize / scale - centerSlice.size as Offset;
452
    outputSize = outputSize - sliceBorder as Size;
453
    inputSize = inputSize - sliceBorder * scale as Size;
454 455 456
  }
  fit ??= centerSlice == null ? BoxFit.scaleDown : BoxFit.fill;
  assert(centerSlice == null || (fit != BoxFit.none && fit != BoxFit.cover));
457 458
  final FittedSizes fittedSizes = applyBoxFit(fit, inputSize / scale, outputSize);
  final Size sourceSize = fittedSizes.source * scale;
459 460
  Size destinationSize = fittedSizes.destination;
  if (centerSlice != null) {
461
    outputSize += sliceBorder!;
462 463 464 465 466
    destinationSize += sliceBorder;
    // We don't have the ability to draw a subset of the image at the same time
    // as we apply a nine-patch stretch.
    assert(sourceSize == inputSize, 'centerSlice was used with a BoxFit that does not guarantee that the image is fully visible.');
  }
467

468 469 470 471 472 473 474 475
  if (repeat != ImageRepeat.noRepeat && destinationSize == outputSize) {
    // There's no need to repeat the image because we're exactly filling the
    // output rect with the image.
    repeat = ImageRepeat.noRepeat;
  }
  final Paint paint = Paint()..isAntiAlias = isAntiAlias;
  if (colorFilter != null)
    paint.colorFilter = colorFilter;
476
  paint.filterQuality = filterQuality;
477 478 479 480 481 482 483 484 485 486 487
  paint.invertColors = invertColors;
  final double halfWidthDelta = (outputSize.width - destinationSize.width) / 2.0;
  final double halfHeightDelta = (outputSize.height - destinationSize.height) / 2.0;
  final double dx = halfWidthDelta + (flipHorizontally ? -alignment.x : alignment.x) * halfWidthDelta;
  final double dy = halfHeightDelta + alignment.y * halfHeightDelta;
  final Offset destinationPosition = rect.topLeft.translate(dx, dy);
  final Rect destinationRect = destinationPosition & destinationSize;

  // Set to true if we added a saveLayer to the canvas to invert/flip the image.
  bool invertedCanvas = false;
  // Output size and destination rect are fully calculated.
488 489 490 491 492 493 494
  if (!kReleaseMode) {
    final ImageSizeInfo sizeInfo = ImageSizeInfo(
      // Some ImageProvider implementations may not have given this.
      source: debugImageLabel ?? '<Unknown Image(${image.width}×${image.height})>',
      imageSize: Size(image.width.toDouble(), image.height.toDouble()),
      displaySize: outputSize,
    );
495 496 497 498 499 500 501 502 503 504
    assert(() {
      if (debugInvertOversizedImages &&
          sizeInfo.decodedSizeInBytes > sizeInfo.displaySizeInBytes + debugImageOverheadAllowance) {
        final int overheadInKilobytes = (sizeInfo.decodedSizeInBytes - sizeInfo.displaySizeInBytes) ~/ 1024;
        final int outputWidth = outputSize.width.toInt();
        final int outputHeight = outputSize.height.toInt();
        FlutterError.reportError(FlutterErrorDetails(
          exception: 'Image $debugImageLabel has a display size of '
            '$outputWidth×$outputHeight but a decode size of '
            '${image.width}×${image.height}, which uses an additional '
505
            '${overheadInKilobytes}KB.\n\n'
506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530
            'Consider resizing the asset ahead of time, supplying a cacheWidth '
            'parameter of $outputWidth, a cacheHeight parameter of '
            '$outputHeight, or using a ResizeImage.',
          library: 'painting library',
          context: ErrorDescription('while painting an image'),
        ));
        // Invert the colors of the canvas.
        canvas.saveLayer(
          destinationRect,
          Paint()..colorFilter = const ColorFilter.matrix(<double>[
            -1,  0,  0, 0, 255,
             0, -1,  0, 0, 255,
             0,  0, -1, 0, 255,
             0,  0,  0, 1,   0,
          ]),
        );
        // Flip the canvas vertically.
        final double dy = -(rect.top + rect.height / 2.0);
        canvas.translate(0.0, -dy);
        canvas.scale(1.0, -1.0);
        canvas.translate(0.0, dy);
        invertedCanvas = true;
      }
      return true;
    }());
531 532
    // Avoid emitting events that are the same as those emitted in the last frame.
    if (!_lastFrameImageSizeInfo.contains(sizeInfo)) {
533
      final ImageSizeInfo? existingSizeInfo = _pendingImageSizeInfo[sizeInfo.source];
534
      if (existingSizeInfo == null || existingSizeInfo.displaySizeInBytes < sizeInfo.displaySizeInBytes) {
535
        _pendingImageSizeInfo[sizeInfo.source!] = sizeInfo;
536
      }
537
      debugOnPaintImage?.call(sizeInfo);
538
      SchedulerBinding.instance!.addPostFrameCallback((Duration timeStamp) {
539 540 541 542 543 544
        _lastFrameImageSizeInfo = _pendingImageSizeInfo.values.toSet();
        if (_pendingImageSizeInfo.isEmpty) {
          return;
        }
        developer.postEvent(
          'Flutter.ImageSizesForFrame',
545
          <String, Object>{
546
            for (ImageSizeInfo imageSizeInfo in _pendingImageSizeInfo.values)
547
              imageSizeInfo.source!: imageSizeInfo.toJson(),
548 549 550 551 552 553 554
          },
        );
        _pendingImageSizeInfo = <String, ImageSizeInfo>{};
      });
    }
  }

555
  final bool needSave = centerSlice != null || repeat != ImageRepeat.noRepeat || flipHorizontally;
Ian Hickson's avatar
Ian Hickson committed
556
  if (needSave)
557
    canvas.save();
Ian Hickson's avatar
Ian Hickson committed
558
  if (repeat != ImageRepeat.noRepeat)
559
    canvas.clipRect(rect);
Ian Hickson's avatar
Ian Hickson committed
560 561 562 563 564
  if (flipHorizontally) {
    final double dx = -(rect.left + rect.width / 2.0);
    canvas.translate(-dx, 0.0);
    canvas.scale(-1.0, 1.0);
    canvas.translate(dx, 0.0);
565 566
  }
  if (centerSlice == null) {
Ian Hickson's avatar
Ian Hickson committed
567
    final Rect sourceRect = alignment.inscribe(
568
      sourceSize, Offset.zero & inputSize,
569
    );
570 571 572
    if (repeat == ImageRepeat.noRepeat) {
      canvas.drawImageRect(image, sourceRect, destinationRect, paint);
    } else {
573
      for (final Rect tileRect in _generateImageTileRects(rect, destinationRect, repeat))
574 575
        canvas.drawImageRect(image, sourceRect, tileRect, paint);
    }
576
  } else {
577
    canvas.scale(1 / scale);
578
    if (repeat == ImageRepeat.noRepeat) {
579
      canvas.drawImageNine(image, _scaleRect(centerSlice, scale), _scaleRect(destinationRect, scale), paint);
580
    } else {
581
      for (final Rect tileRect in _generateImageTileRects(rect, destinationRect, repeat))
582
        canvas.drawImageNine(image, _scaleRect(centerSlice, scale), _scaleRect(tileRect, scale), paint);
583
    }
584
  }
Ian Hickson's avatar
Ian Hickson committed
585
  if (needSave)
586
    canvas.restore();
587 588 589 590

  if (invertedCanvas) {
    canvas.restore();
  }
591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612
}

Iterable<Rect> _generateImageTileRects(Rect outputRect, Rect fundamentalRect, ImageRepeat repeat) sync* {
  int startX = 0;
  int startY = 0;
  int stopX = 0;
  int stopY = 0;
  final double strideX = fundamentalRect.width;
  final double strideY = fundamentalRect.height;

  if (repeat == ImageRepeat.repeat || repeat == ImageRepeat.repeatX) {
    startX = ((outputRect.left - fundamentalRect.left) / strideX).floor();
    stopX = ((outputRect.right - fundamentalRect.right) / strideX).ceil();
  }

  if (repeat == ImageRepeat.repeat || repeat == ImageRepeat.repeatY) {
    startY = ((outputRect.top - fundamentalRect.top) / strideY).floor();
    stopY = ((outputRect.bottom - fundamentalRect.bottom) / strideY).ceil();
  }

  for (int i = startX; i <= stopX; ++i) {
    for (int j = startY; j <= stopY; ++j)
613
      yield fundamentalRect.shift(Offset(i * strideX, j * strideY));
614 615
  }
}
616 617

Rect _scaleRect(Rect rect, double scale) => Rect.fromLTRB(rect.left * scale, rect.top * scale, rect.right * scale, rect.bottom * scale);