Eto.Drawing invert colors of bitmap or image?

clement · April 8, 2024, 1:03am

Hi there,

is it possible to invert the colors of a bitmap or image using Eto.Drawing ?

I mean without iterating pixel by pixel…

thanks,
clement

nathanletwory · April 8, 2024, 5:17am

Check this piece of code where I use System.Drawing.Bitmap to convert to grayscale

github.com

mcneel/RhinoCycles/blob/175a1c7e9d99dba99f1e8c110291e020188e0ae8/CyclesBackground.cs#L223


      
          
          		/// <summary>
          		/// Same as <see cref="HandleWallpaper(ViewInfo, bool)"/>, but re-use old scaletofit setting
          		/// </summary>
          		/// <param name="view"></param>
          		public void HandleWallpaper(ViewInfo view)
          		{
          			HandleWallpaper(view, m_old_scaletofit);
          		}
          
          		public void HandleWallpaper(ViewInfo view, bool scaleToFit)
          		{
          			var file = Rhino.Render.Utilities.FindFile(RhinoDoc.ActiveDoc, view.WallpaperFilename);
          
          			bool modifiedWallpaper = false;
          			modifiedWallpaper |= m_old_hidden != view.WallpaperHidden | m_old_grayscale != view.ShowWallpaperInGrayScale;
          			modifiedWallpaper |= m_old_scaletofit != scaleToFit;
          			modifiedWallpaper |= !m_old_wallpaper.Equals(file);
          			Modified |= modifiedWallpaper;
          
          			if (string.IsNullOrEmpty(file) || !File.Exists(file))

Specifically see the color conversion matrix starting on line 258 and it being applied on 277 to the image attributes and those attributes themselves in turn being used on 323.

clement · April 8, 2024, 9:14pm

Hi @nathanletwory, thank you. I guess there is no equivalent to this:

attr = System.Drawing.Imaging.ImageAttributes()
attr.SetRemapTable(my_color_map)

using Eto ?

_
c.

nathanletwory · April 9, 2024, 5:09am

I don’t think so, I would just use the System.Drawing and System.Drawing.Imaging namespaces, and then convert to an Eto bitmap when done.

clement · April 9, 2024, 11:02pm

Thanks @nathanletwory, i’m not sure if this needs to work on Mac in the future, hence my question for an Eto only way to accomplish it.

_
c.

nathanletwory · April 10, 2024, 3:46am

The code I linked you to also works on Mac as RhinoCycles runs there no problem.

clement · April 10, 2024, 4:11am

Thanks @nathanletwory, these are good news. I’ll use SetRemapTable then.

_
c.

gankeyu · April 10, 2024, 4:50am

SetRemapTable comes from gdiplus, which is kind of unsupported after .NET 6.0. I don’t know whether Rhino has hacks on macos.

clement · April 10, 2024, 4:56am

Hi @gankeyu, thank you for this information. I’ll try what i can do on mac. I’m also looking for a replacement of System.Drawing.Drawing2D.PathGradientBrush then…

_
c.

nathanletwory · April 10, 2024, 8:30am

I don’t know about hacks, that is something I can’t speak to, I just use what I can. Maybe @curtisw can tell more about that.

I just know that the code works in Rhino. Here Rhino 8.7 with a wallpaper set to grayscale, which uses the code that I showed: