BitmapHelper.cs :  » GUI » TreeViewAdv » Aga » Controls » C# / CSharp Open Source

using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Drawing.Imaging;

namespace Aga.Controls{
  public static class BitmapHelper
  {
    [StructLayout(LayoutKind.Sequential)]
    private struct PixelData
    {
      public byte B;
      public byte G;
      public byte R;
      public byte A;
    }

    public static void SetAlphaChanelValue(Bitmap image, byte value)
    {
      if (image == null)
        throw new ArgumentNullException("image");
      if (image.PixelFormat != PixelFormat.Format32bppArgb)
        throw new ArgumentException("Wrong PixelFormat");

      BitmapData bitmapData = image.LockBits(new Rectangle(0, 0, image.Width, image.Height),
                   ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb);
      unsafe
      {
        PixelData* pPixel = (PixelData*)bitmapData.Scan0;
        for (int i = 0; i < bitmapData.Height; i++)
        {
          for (int j = 0; j < bitmapData.Width; j++)
          {
            pPixel->A = value;
            pPixel++;
          }
          pPixel += bitmapData.Stride - (bitmapData.Width * 4);
        }
      }
      image.UnlockBits(bitmapData);
    }
  }
}