Archive of posts filed under the Images category.

Showing images from database in in Silverlight

Posted by Sergey Barskiy on 6 January 2009, 8:22 pm

You can show images in Silverlight using Image control.  You can furthermore bind Source property of the image to byte[] type property of a business object.  You would think this is sufficient, but it is not.  You will need a converter to convert byte array into image source.

Here is the class for converter

public class ImageSourceConverter : IValueConverter
{

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        BitmapImage bitmap = new BitmapImage();
        bitmap.SetSource(new MemoryStream((Byte[])value));
        return bitmap;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

Here is how this class is used in a control:

<UserControl.Resources>
       <helpers:ImageConverter x:Key="ConvertImage"/>
   </UserControl.Resources>

<Image Source="{Binding Path=MyByteArrayPropertyName, Converter={StaticResource ConvertImage}}" />

Filed under Images, Silverlight.
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How to draw bitmaps in code

Posted by Sergey Barskiy on 16 October 2008, 2:07 pm

So, I had a task to create a graph in code

Not an easy task at you can see.  It took me about 12 hours to get it done from scratch.  My class takes the following parameters: 4 values – one for each color and bitmap size (width and height).

Here are some code samples:

Create a bitmap

Bitmap returnValue = new Bitmap(width, height);

Draw axes:

private static void DrawAxes(Bitmap result)
    {
      Pen axesPen = new Pen(Color.Black, 1);
      Graphics worker = Graphics.FromImage(result);
      worker.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
      // draw diagonal axis lines
      worker.DrawLine(axesPen, GetTopLeftCorner(result), GetBottomRightCorner(result));

To draw red color polygon:

PointF[] coordinates = new PointF[] {
          GetRedCorner(result, red),
          redYellowIntersect,
          middle,
          greenRedIntersect};
worker.DrawLine(graphPen, redYellowIntersect, GetRedCorner(result, red));
worker.DrawLine(graphPen, greenRedIntersect, GetRedCorner(result, red));
worker.FillPolygon(redBrush, coordinates);

One fun part was to write a code to determine where two lines intersect.  Here is entire function:

/// <summary>
    /// Find a point at which two lines intersect
    /// </summary>
    /// <param name="line1">First line</param>
    /// <param name="line2">Second line</param>
    /// <param name="middle">Coordinates of the middle of the bitmap</param>
    /// <param name="intersectionType">Does this intersect cross x or y axis</param>
    /// <returns></returns>
    private static PointF LinesIntersect(Line line1, Line line2, PointF middle, IntersectType intersectionType)
    {
      PointF returnValue = new PointF();
      float a1, a2, b1, b2;
      if (line1.End.X == line1.Start.X)
        b1 = (line1.End.Y – line1.Start.Y);
      else
        b1 = (line1.End.Y – line1.Start.Y) / (line1.End.X – line1.Start.X);

      if (line2.End.X == line2.Start.X)
        b2 = (line2.End.Y – line2.Start.Y);
      else
        b2 = (line2.End.Y – line2.Start.Y) / (line2.End.X – line2.Start.X);

      a1 = line1.Start.Y – b1 * line1.Start.X;
      a2 = line2.Start.Y – b2 * line2.Start.X;
      returnValue.X = -(a1 – a2) / (b1 – b2);
      returnValue.Y = a1 + b1 * returnValue.X;

      switch (intersectionType)
      {
        case IntersectType.Horizontal:
          returnValue.Y = middle.Y;
          break;
        case IntersectType.Vertical:
          returnValue.X = middle.X;
          break;
        default:
          throw new Exception("Invalid type");

      }
      return returnValue;
    }

Here are internal classes used in it: 

/// <summary>
    /// Definition for a line - start and end points
    /// </summary>
    private struct Line
    {
      public PointF Start;
      public PointF End;

      public Line(PointF start, PointF end)
      {
        Start = start;
        End = end;
      }
    }

    /// <summary>
    /// Type of intersection - does cross y or x axis
    /// </summary>
    private enum IntersectType
    {
      Horizontal,
      Vertical
    }
Filed under Images.
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