AirScout/ScoutBase/ScoutBase.Core/BitmapHelpers.cs

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Linq;
using System.Text;

namespace ScoutBase.Core
{
    public static class BitmapHelpers
    {

        public static Image SetOpacity(this Image image, float opacity)
        {
            var colorMatrix = new ColorMatrix();
            colorMatrix.Matrix33 = opacity;
            var imageAttributes = new ImageAttributes();
            imageAttributes.SetColorMatrix(
                colorMatrix,
                ColorMatrixFlag.Default,
                ColorAdjustType.Bitmap);
            var output = new Bitmap(image.Width, image.Height);
            using (var gfx = Graphics.FromImage(output))
            {
                gfx.SmoothingMode = SmoothingMode.AntiAlias;
                gfx.DrawImage(
                    image,
                    new Rectangle(0, 0, image.Width, image.Height),
                    0,
                    0,
                    image.Width,
                    image.Height,
                    GraphicsUnit.Pixel,
                    imageAttributes);
            }
            return output;
        }
    }
}