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private Bitmap ChangeColor(Image image, Color color)
{
    Bitmap pic = new Bitmap(image);
    Bitmap newPic = new Bitmap(pic.Width, pic.Height);

    ColorMap[] cMap = new ColorMap[1];

    cMap[0] = new ColorMap();
    cMap[0].OldColor = Color.Black;
    cMap[0].NewColor = color;

    ImageAttributes imageAtributes = new ImageAttributes();
    imageAtributes.SetRemapTable(cMap);

    using (Graphics g = Graphics.FromImage(newPic))
    {
        g.DrawImage(pic, new Rectangle(0, 0, pic.Width, pic.Height), 0, 0, pic.Width, pic.Height, GraphicsUnit.Pixel, imageAtributes);
    }

    return newPic;
}

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ColorMatrix colorMatrix = new ColorMatrix(new float[][] { new float[] { 0.299F, 0.299F, 0.299F, 0, 0 }, new float[] { 0.587F, 0.587F, 0.587F, 0, 0 }, new float[] { 0.114F, 0.114F, 0.114F, 0, 0 }, new float[] { 0, 0, 0, 1, 0 }, new float[] { 0, 0, 0, 0, 1 } });

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unsafe void Test(Bitmap image)
{
        Color color;

        for (Int32 y = 0; y < image.Height; y++)
        {
            for (Int32 x = 0; x < image.Width; x++)
            {
                color = image.GetPixel(x, y);
            }
        }
    }
}

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Bitmap oBitmap;

bitmapData data = oBitmap.LockBits( rBounds, ImageLockMode.Read, oBitmap.PixelFormat );

int iCurrentPosition = iY * data.Stride + (iX * 3);

Color color = Color.FromArgb(data[ iCurrentPosition+2 ],
                             data[ iCurrentPosition+1 ],
                             data[ iCurrentPosition ] );

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            var bmp = new Bitmap(8000, 6000, System.Drawing.Imaging.PixelFormat.Format24bppRgb);

            var fast = new FastBitmap(bmp, true);

            for (int x = 0; x < 8000; x++)
                for (int y = 0; y < 6000; y++)
                fast.SetPixel(x, y, Color.Blue);

            pictureBox1.Image = fast.Bitmap;;