From Wikipedia: hqx ("hq" stands for "high quality" and "x" stands for magnification) is one of the pixel art scaling algorithms developed by Maxim Stepin, used in emulators such as Nestopia, bsnes, ZSNES, Snes9x, FCE Ultra and many more. There are 3 hqx filters: hq2x, hq3x, and hq4x, which magnify by factor of 2, 3, and 4 respectively.
Hqx-dart is a Dart port of hqx-java, which is a port of hqxSharp for C#, which itself is a port of the original hqx C project.
ImageElement image = new ImageElement(src: "mushroom.png");
image.onLoad.listen((Event e){
Hqx.init();
context.drawImage(image, 10, 10);
context.drawImage(Hqx.defaultHq2x(image), 30, 10);
context.drawImage(Hqx.defaultHq3x(image), 70, 10);
context.drawImage(Hqx.defaultHq4x(image), 130, 10);
Hqx.deinit();
}