testing/dart/canvas_test.dart

// Copyright 2013 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.

// @dart = 2.6
import 'dart:async';
import 'dart:io';
import 'dart:typed_data';
import 'dart:ui';
import 'package:image/image.dart' as dart_image;

import 'package:path/path.dart' as path;
import 'package:test/test.dart';

typedef CanvasCallback = void Function(Canvas canvas);

Future<Image> createImage(int width, int height) {
  final Completer<Image> completer = Completer<Image>();
  decodeImageFromPixels(
    Uint8List.fromList(List<int>.generate(
      width * height * 4,
      (int pixel) => pixel % 255,
    )),
    width,
    height,
    PixelFormat.rgba8888,
    (Image image) {
      completer.complete(image);
    },
  );

  return completer.future;
}

void testCanvas(CanvasCallback callback) {
  try {
    callback(Canvas(PictureRecorder(), const Rect.fromLTRB(0.0, 0.0, 0.0, 0.0)));
  } catch (error) { } // ignore: empty_catches
}

void testNoCrashes() {
  test('canvas APIs should not crash', () async {
    final Paint paint = Paint();
    const Rect rect = Rect.fromLTRB(double.nan, double.nan, double.nan, double.nan);
    final RRect rrect = RRect.fromRectAndCorners(rect);
    const Offset offset = Offset(double.nan, double.nan);
    final Path path = Path();
    const Color color = Color(0);
    final Paragraph paragraph = ParagraphBuilder(ParagraphStyle()).build();

    final PictureRecorder recorder = PictureRecorder();
    final Canvas recorderCanvas = Canvas(recorder);
    recorderCanvas.scale(1.0, 1.0);
    final Picture picture = recorder.endRecording();
    final Image image = await picture.toImage(1, 1);

    try { Canvas(null, null); } catch (error) { } // ignore: empty_catches
    try { Canvas(null, rect); } catch (error) { } // ignore: empty_catches
    try { Canvas(PictureRecorder(), null); } catch (error) { } // ignore: empty_catches
    try { Canvas(PictureRecorder(), rect); } catch (error) { } // ignore: empty_catches

    try {
      PictureRecorder()
        ..endRecording()
        ..endRecording()
        ..endRecording();
    } catch (error) { } // ignore: empty_catches

    testCanvas((Canvas canvas) => canvas.clipPath(path));
    testCanvas((Canvas canvas) => canvas.clipRect(rect));
    testCanvas((Canvas canvas) => canvas.clipRRect(rrect));
    testCanvas((Canvas canvas) => canvas.drawArc(rect, 0.0, 0.0, false, paint));
    testCanvas((Canvas canvas) => canvas.drawAtlas(image, <RSTransform>[], <Rect>[], <Color>[], BlendMode.src, rect, paint));
    testCanvas((Canvas canvas) => canvas.drawCircle(offset, double.nan, paint));
    testCanvas((Canvas canvas) => canvas.drawColor(color, BlendMode.src));
    testCanvas((Canvas canvas) => canvas.drawDRRect(rrect, rrect, paint));
    testCanvas((Canvas canvas) => canvas.drawImage(image, offset, paint));
    testCanvas((Canvas canvas) => canvas.drawImageNine(image, rect, rect, paint));
    testCanvas((Canvas canvas) => canvas.drawImageRect(image, rect, rect, paint));
    testCanvas((Canvas canvas) => canvas.drawLine(offset, offset, paint));
    testCanvas((Canvas canvas) => canvas.drawOval(rect, paint));
    testCanvas((Canvas canvas) => canvas.drawPaint(paint));
    testCanvas((Canvas canvas) => canvas.drawParagraph(paragraph, offset));
    testCanvas((Canvas canvas) => canvas.drawPath(path, paint));
    testCanvas((Canvas canvas) => canvas.drawPicture(picture));
    testCanvas((Canvas canvas) => canvas.drawPoints(PointMode.points, <Offset>[], paint));
    testCanvas((Canvas canvas) => canvas.drawRawAtlas(image, Float32List(0), Float32List(0), Int32List(0), BlendMode.src, rect, paint));
    testCanvas((Canvas canvas) => canvas.drawRawPoints(PointMode.points, Float32List(0), paint));
    testCanvas((Canvas canvas) => canvas.drawRect(rect, paint));
    testCanvas((Canvas canvas) => canvas.drawRRect(rrect, paint));
    testCanvas((Canvas canvas) => canvas.drawShadow(path, color, double.nan, null));
    testCanvas((Canvas canvas) => canvas.drawShadow(path, color, double.nan, false));
    testCanvas((Canvas canvas) => canvas.drawShadow(path, color, double.nan, true));
    testCanvas((Canvas canvas) => canvas.drawVertices(Vertices(VertexMode.triangles, <Offset>[]), null, paint));
    testCanvas((Canvas canvas) => canvas.getSaveCount());
    testCanvas((Canvas canvas) => canvas.restore());
    testCanvas((Canvas canvas) => canvas.rotate(double.nan));
    testCanvas((Canvas canvas) => canvas.save());
    testCanvas((Canvas canvas) => canvas.saveLayer(rect, paint));
    testCanvas((Canvas canvas) => canvas.saveLayer(null, null));
    testCanvas((Canvas canvas) => canvas.scale(double.nan, double.nan));
    testCanvas((Canvas canvas) => canvas.skew(double.nan, double.nan));
    testCanvas((Canvas canvas) => canvas.transform(null));
    testCanvas((Canvas canvas) => canvas.translate(double.nan, double.nan));
  });
}

/// @returns true When the images are resonably similar.
/// @todo Make the search actually fuzzy to a certain degree.
Future<bool> fuzzyCompareImages(Image golden, Image img) async {
  if (golden.width != img.width || golden.height != img.height) {
    return false;
  }
  int getPixel(ByteData data, int x, int y) => data.getUint32((x + y * golden.width) * 4);
  final ByteData goldenData = await golden.toByteData();
  final ByteData imgData = await img.toByteData();
  for (int y = 0; y < golden.height; y++) {
    for (int x = 0; x < golden.width; x++) {
      if (getPixel(goldenData, x, y) != getPixel(imgData, x, y)) {
        return false;
      }
    }
  }
  return true;
}

/// @returns true When the images are resonably similar.
Future<bool> fuzzyGoldenImageCompare(
    Image image, String goldenImageName) async {
  final String imagesPath = path.join('flutter', 'testing', 'resources');
  final File file = File(path.join(imagesPath, goldenImageName));

  bool areEqual = false;

  if (file.existsSync()) {
    final Uint8List goldenData = await file.readAsBytes();

    final Codec codec = await instantiateImageCodec(goldenData);
    final FrameInfo frame = await codec.getNextFrame();
    expect(frame.image.height, equals(image.width));
    expect(frame.image.width, equals(image.height));

    areEqual = await fuzzyCompareImages(frame.image, image);
  }

  if (!areEqual) {
    final ByteData pngData = await image.toByteData();
    final ByteBuffer buffer = pngData.buffer;
    final dart_image.Image png = dart_image.Image.fromBytes(
        image.width, image.height, buffer.asUint8List());
    final String outPath = path.join(imagesPath, 'found_' + goldenImageName);
    File(outPath)..writeAsBytesSync(dart_image.encodePng(png));
    print('wrote: ' + outPath);
  }
  return areEqual;
}

void main() {
  testNoCrashes();

  test('Simple .toImage', () async {
    final PictureRecorder recorder = PictureRecorder();
    final Canvas canvas = Canvas(recorder);
    final Path circlePath = Path()
      ..addOval(
          Rect.fromCircle(center: const Offset(40.0, 40.0), radius: 20.0));
    final Paint paint = Paint()
      ..isAntiAlias = false
      ..style = PaintingStyle.fill;
    canvas.drawPath(circlePath, paint);
    final Picture picture = recorder.endRecording();
    final Image image = await picture.toImage(100, 100);
    expect(image.width, equals(100));
    expect(image.height, equals(100));

    final bool areEqual =
        await fuzzyGoldenImageCompare(image, 'canvas_test_toImage.png');
    expect(areEqual, true);
  });

  Gradient makeGradient() {
    return Gradient.linear(
      Offset.zero,
      const Offset(100, 100),
      const <Color>[Color(0xFF4C4D52), Color(0xFF202124)],
    );
  }

  test('Simple gradient', () async {
    Paint.enableDithering = false;
    final PictureRecorder recorder = PictureRecorder();
    final Canvas canvas = Canvas(recorder);
    final Paint paint = Paint()..shader = makeGradient();
    canvas.drawPaint(paint);
    final Picture picture = recorder.endRecording();
    final Image image = await picture.toImage(100, 100);
    expect(image.width, equals(100));
    expect(image.height, equals(100));

    final bool areEqual =
        await fuzzyGoldenImageCompare(image, 'canvas_test_gradient.png');
    expect(areEqual, true);
  }, skip: !Platform.isLinux); // https://github.com/flutter/flutter/issues/53784

  test('Simple dithered gradient', () async {
    Paint.enableDithering = true;
    final PictureRecorder recorder = PictureRecorder();
    final Canvas canvas = Canvas(recorder);
    final Paint paint = Paint()..shader = makeGradient();
    canvas.drawPaint(paint);
    final Picture picture = recorder.endRecording();
    final Image image = await picture.toImage(100, 100);
    expect(image.width, equals(100));
    expect(image.height, equals(100));

    final bool areEqual =
        await fuzzyGoldenImageCompare(image, 'canvas_test_dithered_gradient.png');
    expect(areEqual, true);
  }, skip: !Platform.isLinux); // https://github.com/flutter/flutter/issues/53784

  test('Image size reflected in picture size for image*, drawAtlas, and drawPicture methods', () async {
    final Image image = await createImage(100, 100);
    final PictureRecorder recorder = PictureRecorder();
    final Canvas canvas = Canvas(recorder);
    const Rect rect = Rect.fromLTWH(0, 0, 100, 100);
    canvas.drawImage(image, Offset.zero, Paint());
    canvas.drawImageRect(image, rect, rect, Paint());
    canvas.drawImageNine(image, rect, rect, Paint());
    canvas.drawAtlas(image, <RSTransform>[], <Rect>[], <Color>[], BlendMode.src, rect, Paint());
    final Picture picture = recorder.endRecording();

    // Some of the numbers here appear to utilize sharing/reuse of common items,
    // e.g. of the Paint() or same `Rect` usage, etc.
    // The raw utilization of a 100x100 picture here should be 53333:
    // 100 * 100 * 4 * (4/3) = 53333.333333....
    // To avoid platform specific idiosyncrasies and brittleness against changes
    // to Skia, we just assert this is _at least_ 4x the image size.
    const int minimumExpected = 53333 * 4;
    expect(picture.approximateBytesUsed, greaterThan(minimumExpected));

    final PictureRecorder recorder2 = PictureRecorder();
    final Canvas canvas2 = Canvas(recorder2);
    canvas2.drawPicture(picture);
    final Picture picture2 = recorder2.endRecording();

    expect(picture2.approximateBytesUsed, greaterThan(minimumExpected));
  });

  test('Vertex buffer size reflected in picture size for drawVertices', () async {
    final PictureRecorder recorder = PictureRecorder();
    final Canvas canvas = Canvas(recorder);

    const int uint16max = 65535;

    final Int32List colors = Int32List(uint16max);
    final Float32List coords = Float32List(uint16max * 2);
    final Uint16List indices = Uint16List(uint16max);
    final Float32List positions = Float32List(uint16max * 2);
    colors[0] = const Color(0xFFFF0000).value;
    colors[1] = const Color(0xFF00FF00).value;
    colors[2] = const Color(0xFF0000FF).value;
    colors[3] = const Color(0xFF00FFFF).value;
    indices[1] = indices[3] = 1;
    indices[2] = indices[5] = 3;
    indices[4] = 2;
    positions[2] = positions[4] = positions[5] = positions[7] = 250.0;

    final Vertices vertices = Vertices.raw(
      VertexMode.triangles,
      positions,
      textureCoordinates: coords,
      colors: colors,
      indices: indices,
    );
    canvas.drawVertices(vertices, BlendMode.src, Paint());
    final Picture picture = recorder.endRecording();


    const int minimumExpected = uint16max * 4;
    expect(picture.approximateBytesUsed, greaterThan(minimumExpected));

    final PictureRecorder recorder2 = PictureRecorder();
    final Canvas canvas2 = Canvas(recorder2);
    canvas2.drawPicture(picture);
    final Picture picture2 = recorder2.endRecording();

    expect(picture2.approximateBytesUsed, greaterThan(minimumExpected));
  });

  test('Path reflected in picture size for drawPath, clipPath, and drawShadow', () async {
    final PictureRecorder recorder = PictureRecorder();
    final Canvas canvas = Canvas(recorder);
    final Path path = Path();
    for (int i = 0; i < 10000; i++) {
      path.lineTo(5, 9);
      path.lineTo(i.toDouble(), i.toDouble());
    }
    path.close();
    canvas.drawPath(path, Paint());
    canvas.drawShadow(path, const Color(0xFF000000), 5.0, false);
    canvas.clipPath(path);
    final Picture picture = recorder.endRecording();

    // Slightly fuzzy here to allow for platform specific differences
    // Measurement on macOS: 541078
    expect(picture.approximateBytesUsed, greaterThan(530000));
  });
}