rowSpan after Image.Load<Bgr24>(filename.bmp) fails on Linux, same image file + code work on Windows

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of ImageSharp
• I have verified if the problem exist in both DEBUG and RELEASE mode
• I have searched open and closed issues to ensure it has not already been reported

Description

For me the unit test below works for Windows, but fails for Linux.
When i change "Image.Load<Bgr24>(sourceFilePath)" to Image.Load(sourceFilePath) it works for both.

Steps to Reproduce

    [Theory]
    [InlineData("TestData/Screens/white.bmp", 255)]
    public void DummyTest(string sourceFilePath, byte expected_rgb)
    {
        using (var image = Image.Load<Bgr24>(sourceFilePath))
        {
            for (int y = 0; y < image.Height; y++)
            {
                var rowSpan = image.GetRowSpan(y);
                for (int x = 0; x < image.Width; x++)
                {
                    if (expected_rgb != rowSpan[x].R ||
                        expected_rgb != rowSpan[x].G ||
                        expected_rgb != rowSpan[x].B)
                    {
                        output.WriteLine(string.Format("failed at y={0} x={1}", y, x));
                        output.WriteLine(string.Format("r={0} g={1} b={2}", rowSpan[x].R, rowSpan[x].G, rowSpan[x].B));
                    }

                    Assert.Equal(expected_rgb, rowSpan[x].R);
                    Assert.Equal(expected_rgb, rowSpan[x].G);
                    Assert.Equal(expected_rgb, rowSpan[x].B);
                }
            }
        }
    }

System Configuration

• Linux: Ubuntu-Server 14.04.1 LTS Trusty Tahr (3.13.0-85-generic #129-Ubuntu SMP Thu Mar 17 20:50:15 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux)

• Windows: Windwos 10 64bit

• ImageSharp version: ImageSharp 1.0.0-alpha9-00182

• Other ImageSharp packages and versions:

• Environment (Operating system, version and so on):

• .NET Framework version: .Net Core 2.0, failed with .Net Core 1.1 as well

• Additional information:

white.zip

GetRowSpan is no longer part of the public API, so this issue makes no longer sense

[JimBobSquarePants]

It will most likely be for v1 though so I'd like to keep it open and see if anything has changed by then.

[antonfirsov]

@pammann-work Is this about assertions failing (and not Span-related exceptions and crashes) right?
Can you do a favor for us, and try changing your test to use the image[x, y] indexer instead of row span? :)

If my assumptions are right right, this has nothing to do with Span<T>. It is a strange pixel-type conversion issue we experience on Linux. I'm quite sure we already had an open issue for this, but I was unable to find it. @JimBobSquarePants @dlemstra do you remember which one is it?

[antonfirsov]

Wait ... I just realized this issue has been opened in August. So .. this is the issue I was talking about. I need more cofee.

[antonfirsov]

This has been most likely fixed by #591 (possible duplicate of #576).

We plan to expose .GetRowSpan() again soon (see #565)