blob: 038ed0f985a15e7ebfd57ee75def98f322dbd640 [file] [log] [blame]
// 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:async';
import 'dart:typed_data';
import 'dart:ui' as ui;
import 'package:flutter/foundation.dart';
import 'package:flutter/painting.dart';
import 'test_async_utils.dart';
final Map<int, ui.Image> _cache = <int, ui.Image>{};
/// Creates an arbitrarily sized image for testing.
/// If the [cache] parameter is set to true, the image will be cached for the
/// rest of this suite. This is normally desirable, assuming a test suite uses
/// images with the same dimensions in most tests, as it will save on memory
/// usage and CPU time over the course of the suite. However, it should be
/// avoided for images that are used only once in a test suite, especially if
/// the image is large, as it will require holding on to the memory for that
/// image for the duration of the suite.
/// This method requires real async work, and will not work properly in the
/// [FakeAsync] zones set up by [testWidgets]. Typically, it should be invoked
/// as a setup step before [testWidgets] are run, such as [setUp] or [setUpAll].
/// If needed, it can be invoked using [WidgetTester.runAsync].
Future<ui.Image> createTestImage({
int width = 1,
int height = 1,
bool cache = true,
}) => TestAsyncUtils.guard(() async {
assert(width != null && width > 0);
assert(height != null && height > 0);
assert(cache != null);
final int cacheKey = hashValues(width, height);
if (cache && _cache.containsKey(cacheKey)) {
return _cache[cacheKey]!.clone();
final ui.Image image = await _createImage(width, height);
if (cache) {
_cache[cacheKey] = image.clone();
return image;
Future<ui.Image> _createImage(int width, int height) async {
if (kIsWeb) {
return await _webCreateTestImage(
width: width,
height: height,
final Completer<ui.Image> completer = Completer<ui.Image>();
Uint8List.fromList(List<int>.filled(width * height * 4, 0, growable: false)),
(ui.Image image) {
return await completer.future;
/// Web doesn't support [decodeImageFromPixels]. Instead, generate a 1bpp BMP
/// and just use [instantiateImageCodec].
// TODO(dnfield): Remove this when
// is resolved.
Future<ui.Image> _webCreateTestImage({
required int width,
required int height,
}) async {
// See for format examples.
final int bufferSize = 0x36 + (width * height);
final ByteData bmpData = ByteData(bufferSize);
// 'BM' header
bmpData.setUint8(0x00, 0x42);
bmpData.setUint8(0x01, 0x4D);
// Size of data
bmpData.setUint32(0x02, bufferSize, Endian.little);
// Offset where pixel array begins
bmpData.setUint32(0x0A, 0x36, Endian.little);
// Bytes in DIB header
bmpData.setUint32(0x0E, 0x28, Endian.little);
// width
bmpData.setUint32(0x12, width, Endian.little);
// height
bmpData.setUint32(0x16, height, Endian.little);
// Color panes
bmpData.setUint16(0x1A, 0x01, Endian.little);
// bpp
bmpData.setUint16(0x1C, 0x01, Endian.little);
// no compression
bmpData.setUint32(0x1E, 0x00, Endian.little);
// raw bitmap data size
bmpData.setUint32(0x22, width * height, Endian.little);
// print DPI width
bmpData.setUint32(0x26, width, Endian.little);
// print DPI height
bmpData.setUint32(0x2A, height, Endian.little);
// colors in the palette
bmpData.setUint32(0x2E, 0x00, Endian.little);
// important colors
bmpData.setUint32(0x32, 0x00, Endian.little);
// rest of data is zeroed as black pixels.
final ui.Codec codec = await ui.instantiateImageCodec(
final ui.FrameInfo frameInfo = await codec.getNextFrame();
return frameInfo.image;