public static void OutputIsCloseTo(this Graphics graphics,
string pathToReferenceImage,
float tolerance = 0.05f)
{
if (!File.Exists(pathToReferenceImage))
{
graphics.SaveAsPng(pathToReferenceImage);
throw new FileNotFoundException("No reference present, generated one");
}
var reference = SurfaceFactory.FromFile(pathToReferenceImage);
if (reference.Size != graphics.OutputSize)
{
throw new ArgumentException("Wrong reference image size");
}
var refPixels = new ColorRGB888[reference.PixelCount];
reference.ReadPixels(ref refPixels);
var ms = new MemoryStream();
graphics.SaveAsPng(ms);
ms.Seek(0, SeekOrigin.Begin);
var actual = SurfaceFactory.FromStream(ms, new PngDecoder());
var actualPixels = new ColorRGB888[reference.PixelCount];
actual.ReadPixels(ref actualPixels);
reference.Dispose();
actual.Dispose();
var difference = 0.0f;
for (int i = 0; i < refPixels.Length; i++)
{
var refColor = refPixels[i];
var actualColor = actualPixels[i];
if (refColor.Equals(actualColor))
{
continue;
}
difference += Math.Abs(refColor.R - actualColor.R) / 255.0f;
difference += Math.Abs(refColor.G - actualColor.G) / 255.0f;
difference += Math.Abs(refColor.B - actualColor.B) / 255.0f;
}
difference /= reference.PixelCount;
difference.Should().BeLessOrEqualTo(tolerance);
}