How to create a simple glass effect

Question

I am currently painting a light blue, partly transparent overlay over owner-drawn objects to indicate certain state. It's OK but I thought that it would be even nicer if I could at some sort of glass effect to further establish the idea that the particular object has "something" overlaid over the top of it.

I thought that some glass streaks, for example, in addition to the blue transparency would lend a nice effect.

I've Googled around for GDI+ (and others) algorithms to do simple things painting like this but have come up empty. Links to any (fairly simple) algorithms in any language would be appreciated. I prefer .NET but can figure out the painting from pseudo-code on up.

Sorry, shoul've also specified that I need to target WinXP and using .NET version 2.0 - So unable to use WPF or Vista/Win7 goodies.

Answer 1

You could try the Aero Glass function, if you are using Vista or Windows 7.

These might be helpful:

http://msdn.microsoft.com/en-us/library/aa969537%28VS.85%29.aspx#blurbehind http://msdn.microsoft.com/en-us/library/ms748975.aspx

Answer 2

I've not done this myself but, have used codeproject source to render a sample...Try this:

http://www.codeproject.com/KB/GDI-plus/Image-Glass-Reflection.aspx

public static Image DrawReflection(Image _Image, Color _BackgroundColor, int _Reflectivity)
{
    // Calculate the size of the new image
    int height = (int)(_Image.Height + (_Image.Height * ((float)_Reflectivity / 255)));
    Bitmap newImage = new Bitmap(_Image.Width, height, PixelFormat.Format24bppRgb);
    newImage.SetResolution(_Image.HorizontalResolution, _Image.VerticalResolution);

    using (Graphics graphics = Graphics.FromImage(newImage))
    {
        // Initialize main graphics buffer
        graphics.Clear(_BackgroundColor);
        graphics.DrawImage(_Image, new Point(0, 0));
        graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
        Rectangle destinationRectangle = new Rectangle(0, _Image.Size.Height, 
                                         _Image.Size.Width, _Image.Size.Height);

        // Prepare the reflected image
        int reflectionHeight = (_Image.Height * _Reflectivity) / 255;
        Image reflectedImage = new Bitmap(_Image.Width, reflectionHeight);

        // Draw just the reflection on a second graphics buffer
        using (Graphics gReflection = Graphics.FromImage(reflectedImage))
        {
            gReflection.DrawImage(_Image, 
               new Rectangle(0, 0, reflectedImage.Width, reflectedImage.Height),
               0, _Image.Height - reflectedImage.Height, reflectedImage.Width, 
               reflectedImage.Height, GraphicsUnit.Pixel);
        }
        reflectedImage.RotateFlip(RotateFlipType.RotateNoneFlipY);
        Rectangle imageRectangle = 
            new Rectangle(destinationRectangle.X, destinationRectangle.Y,
            destinationRectangle.Width, 
            (destinationRectangle.Height * _Reflectivity) / 255);

        // Draw the image on the original graphics
        graphics.DrawImage(reflectedImage, imageRectangle);

        // Finish the reflection using a gradiend brush
        LinearGradientBrush brush = new LinearGradientBrush(imageRectangle,
               Color.FromArgb(255 - _Reflectivity, _BackgroundColor),
                _BackgroundColor, 90, false);
        graphics.FillRectangle(brush, imageRectangle);
    }

    return newImage;
}

Answer 3

I was actually able to achieve a basic glass effect by overlaying my image with a rectangle about one third the size of the image below that contains a gradient fill of white that starts at 25% opacity and goes to 75% opacity. This is single bit of painting produces a glassy "streak" that I was happy with. The same idea could be repeated a number of times with a variety of rect widths to produce several "streaks" that will give the illusion of a glass overlay.