Image masking

Image masking (simplified image segmentation) is the process of dividing image to background and foreground parts. It is widely used for recognition, diagnostics, computer vision.

Example of masked image with changed background is presented below.

Fig. 1 (a) Original image	(b) Manually masked image	(c) Automatically masked image with segmentation algorithm

Here we can observe on figures 1 - b, c image masking results - background and foreground of initial image 1 - a.

Aspose.Imaging supports the following types of masking.

• Manual Masking - Using a set of ROIs as the mask. The ROIs for each slice are used to define the mask. Needed additional user input.
• Auto Masking - Automatic mode that does not require from user lot of input data, but can be not so accurate.  

Aspose.Imaging supports few automatic masking algorithms, among them: K-means, Watershed and Graph Cut algorithm (one of proposed automatic methods).

Below we can observe masking results of original image.

Original image	1. K-means image segmentation algorithm (Value metric : Color intensity)	2. K-means image segmentation algorithm (Value metric : Color intensity), with indicating rectangular area for foreground	3. K-means image segmentation algorithm (Value metric : Color intensity * Euclidean distance)	4. Marker-controlled Watershed algorithm	5. Graph Cut algorithm (with indicating areas by user)

Manual masking

The following code snippet provided below demonstrates how to apply manual masking to a raster image.

using Aspose.Imaging;
using Aspose.Imaging.FileFormats.Png;
using Aspose.Imaging.ImageOptions;
using Aspose.Imaging.Masking;
using Aspose.Imaging.Masking.Options;
using Aspose.Imaging.Masking.Result;
using Aspose.Imaging.Shapes;
using Aspose.Imaging.Sources;
using System.IO;

string templatesFolder = @"c:\Users\USER\Downloads\templates\";
string dataDir = templatesFolder;

string sourceFileName = dataDir + "couple.png";
GraphicsPath manualMask = new GraphicsPath();
Figure firstFigure = new Figure();
firstFigure.AddShape(new EllipseShape(new RectangleF(100, 30, 40, 40)));
firstFigure.AddShape(new RectangleShape(new RectangleF(10, 200, 50, 30)));
manualMask.AddFigure(firstFigure);
GraphicsPath subPath = new GraphicsPath();
Figure secondFigure = new Figure();
secondFigure.AddShape(
    new PolygonShape(
     new PointF[]
     {
         new PointF(310, 100), new PointF(350, 200), new PointF(250, 200)

     }, true));

secondFigure.AddShape(new PieShape(new RectangleF(10, 10, 80, 80), 30, 120));
subPath.AddFigure(secondFigure);
manualMask.AddPath(subPath);
using (RasterImage image = (RasterImage)Image.Load(sourceFileName))
{
    MaskingOptions maskingOptions = new MaskingOptions()
    {
        Method = SegmentationMethod.Manual,
        Args = new ManualMaskingArgs
        {
            Mask = manualMask
        },
        Decompose = false,
        ExportOptions =
      new PngOptions()
      {
          ColorType = PngColorType.TruecolorWithAlpha,
          Source = new StreamSource(new MemoryStream())
      },
    };
    MaskingResult results = new ImageMasking(image).Decompose(maskingOptions);
    // Saving final masking result.
    using (RasterImage resultImage = (RasterImage)results[1].GetImage())
    {
        resultImage.Save(dataDir + "result.png", new PngOptions() { ColorType = PngColorType.TruecolorWithAlpha });
    }
}       

File.Delete(dataDir + "result.png");

Auto masking

The following code snippet provided below demonstrates how to apply auto masking to a raster image.

using Aspose.Imaging;
using Aspose.Imaging.FileFormats.Png;
using Aspose.Imaging.ImageOptions;
using Aspose.Imaging.Masking;
using Aspose.Imaging.Masking.Options;
using Aspose.Imaging.Masking.Result;
using Aspose.Imaging.Sources;
using System;
using System.IO;

string templatesFolder = @"c:\Users\USER\Downloads\templates\";
string dataDir = templatesFolder;

MaskingResult results;
using (RasterImage image = (RasterImage)Image.Load(dataDir + "couple.jpg"))
{
    // To use Graph Cut with auto calculated strokes, AutoMaskingGraphCutOptions is used.
    AutoMaskingGraphCutOptions options = new AutoMaskingGraphCutOptions
    {
        // Indicating that a new calculation of the default strokes should be performed during the image decomposition.
        CalculateDefaultStrokes = true,
        // Setting post-process feathering radius based on the image size.
        FeatheringRadius = (Math.Max(image.Width, image.Height) / 500) + 1,
        Method = SegmentationMethod.GraphCut,
        Decompose = false,
        ExportOptions =
                                                        new PngOptions()
                                                        {
                                                            ColorType = PngColorType.TruecolorWithAlpha,
                                                            Source = new FileCreateSource(dataDir + "result.png")
                                                        },
        BackgroundReplacementColor = Color.Transparent
    };

    results = new ImageMasking(image).Decompose(options);

    using (RasterImage resultImage = (RasterImage)results[1].GetImage())
    {
        resultImage.Save(dataDir + "result2.png", new PngOptions() { ColorType = PngColorType.TruecolorWithAlpha });
    }
}



File.Delete(dataDir + "result.png");
File.Delete(dataDir + "result2.png");