Replace System.Drawing with SixLabors.ImageSharp

[ahouts]

Microsoft recommends switching to a third party library for cross platform image manipulation:
https://docs.microsoft.com/en-us/dotnet/core/compatibility/core-libraries/6.0/system-drawing-common-windows-only

I implemented the Save/Load bitmap functions with SixLabors.ImageSharp, all examples seem to work on my system now.

closes #3

Feel free to close this if you want to take a different approach, I was mostly interested in getting it to work on my system.

[alexdmiller]

I am still seeing this error on macOS:

Unhandled exception. System.TypeInitializationException: The type initializer for 'GUI' threw an exception.
 ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at GUI..cctor() in /Users/alex/projects/MarkovJunior-2/source/GUI.cs:line 30
   --- End of inner exception stack trace ---
   at GUI.Draw(String name, Branch root, Branch current, Int32[] bitmap, Int32 WIDTH, Int32 HEIGHT, Dictionary`2 palette)
   at Program.Main() in /Users/alex/projects/MarkovJunior-2/source/Program.cs:line 67

[ersinesen]

You should clone the correct branch:
git clone --branch replace-System.Drawing-with-SixLabors.ImageSharp https://github.com/ahouts/MarkovJunior.git

And check the branch:
git branch -a

[PaulusParssinen]

I wonder if you can use Bgra32 directly so you don't need to swap the endianness manually 🤔

[ahouts]

I wonder if you can use Bgra32 directly so you don't need to swap the endianness manually 🤔

Yeah that would probably be a better approach. I assumed the inverted byte order was endian shenanigans, so I didn't even think to check if the library supported it.
I'll switch to using that when I get home.

[ajzaff]

Works great on Debian Linux. Thanks for writing it.

[Sergio0694]

Love ImageSharp being used! 😄
I've left with some performance/memory improvements that can be done though.

[Sergio0694]

You can use a using to avoid the explicit call to Dispose.
But most importantly, you can vectorize all this with the built-in API to copy the pixel buffer:

Suggested change

	var image = Image.Load<Bgra32>(filename);
	int width = image.Width, height = image.Height;
	var result = new int[width * height];
	for (var j = 0; j < height; j += 1)
	{
	for (var i = 0; i < width; i += 1)
	{
	result[j * width + i] = unchecked((int) image[i, j].Bgra);
	}
	}
	image.Dispose();
	using var image = Image.Load<Bgra32>(filename);
	int width = image.Width;
	int height = image.Height;
	int[] result = new int[width * height];
	image.CopyPixelDataTo(MemoryMarshal.Cast<int, Bgra32>(result));

[Sergio0694]

You can use a using and skip the whole allocation + copy by wrapping the source directly:

Suggested change

	var formattedData = new Bgra32[data.Length];
	for (var i = 0; i < data.Length; i += 1)
	{
	formattedData[i] = new Bgra32
	{
	Bgra = unchecked((uint) data[i])
	};
	}
	var image = Image.WrapMemory(Configuration.Default, new Memory<Bgra32>(formattedData), width, height);
	image.SaveAsPng(filename);
	image.Dispose();
	fixed (int* pData = data)
	{
	using var image = Image.WrapMemory<Bgra32>(pData, width, height);
	image.SaveAsPng(filename);
	}

A couple notes:

• Need to add <AllowUnsafeBlocks>true</AllowUnsafeBlocks> to the .csproj for this
• Make sure to add width/height validation as well before this suggested code.

[JimBobSquarePants]

Strongly recommend that this advice is followed. @Sergio0694 helped a lot to design and optimize the ImageSharp APIs

[mxgmn]

Thanks @Sergio0694 and @JimBobSquarePants, I updated it!

[ahouts]

Love ImageSharp being used! smile I've left with some performance/memory improvements that can be done though.

Doesn't seem likely this PR will be merged given @mxgmn's response on #3 and here: #9 (comment). TBH I can appreciate the zero dependency approach @mxgmn seems to be going for given the only dependency this project had has caused issues.

I'll leave this PR open though so in the interim it has visibility until the permanent solution is implemented.