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    <pre><code> public static Bitmap getGrayscale(Bitmap hc){ Bitmap result = new Bitmap(hc.Width, hc.Height); ColorMatrix colorMatrix = new ColorMatrix(new float[][]{ new float[]{0.5f,0.5f,0.5f,0,0}, new float[]{0.5f,0.5f,0.5f,0,0}, new float[]{0.5f,0.5f,0.5f,0,0}, new float[]{0,0,0,1,0,0}, new float[]{0,0,0,0,1,0}, new float[]{0,0,0,0,0,1}}); using (Graphics g = Graphics.FromImage(result)) { ImageAttributes attributes = new ImageAttributes(); attributes.SetColorMatrix(colorMatrix); g.DrawImage(hc, new Rectangle(0, 0, hc.Width, hc.Height), 0, 0, hc.Width, hc.Height, GraphicsUnit.Pixel, attributes); } return result; } </code></pre> <p>That is actually quite complex problem. In my example, basically I create a filter and apply it to the existing bitmap, with some nifty matrix calculation. I solved it while ago, trying to solve <a href="https://stackoverflow.com/questions/3983508/verify-image-sequence">this</a> problem. </p> <h2>Edit</h2> <p>VB people like full examples, maybe do C# as well.</p> <p><img src="https://i.stack.imgur.com/g7ZAs.png" alt="enter image description here"></p> <p>Drop 2 buttons and a picture box onto a form, and use code:</p> <pre><code>using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Drawing.Imaging; namespace gray { public partial class Example : Form { public Example() { InitializeComponent(); } public static Bitmap getGrayscale(Bitmap hc) { Bitmap result = new Bitmap(hc.Width, hc.Height); ColorMatrix colorMatrix = new ColorMatrix(new float[][]{ new float[]{0.5f,0.5f,0.5f,0,0}, new float[]{0.5f,0.5f,0.5f,0,0}, new float[]{0.5f,0.5f,0.5f,0,0}, new float[]{0,0,0,1,0,0}, new float[]{0,0,0,0,1,0}, new float[]{0,0,0,0,0,1}}); using (Graphics g = Graphics.FromImage(result)) { ImageAttributes attributes = new ImageAttributes(); attributes.SetColorMatrix(colorMatrix); g.DrawImage(hc, new Rectangle(0, 0, hc.Width, hc.Height), 0, 0, hc.Width, hc.Height, GraphicsUnit.Pixel, attributes); } return result; } private void button1_Click(object sender, EventArgs e) { OpenFileDialog fDialog = new OpenFileDialog(); fDialog.Title = "Open Image File"; fDialog.Filter = "PNG Files|*.png|Bitmap Files|*.bmp"; fDialog.InitialDirectory = @"C:\"; if (fDialog.ShowDialog() == DialogResult.OK) this.pictureBox1.ImageLocation = fDialog.FileName.ToString(); } private void button2_Click(object sender, EventArgs e) { if (this.pictureBox1.Image == null) { MessageBox.Show("Sorry no image to alter."); return; } this.pictureBox1.Image = getGrayscale((Bitmap)this.pictureBox1.Image); } } } </code></pre> <p>Yes, this works and colors are balanced correctly. </p> <p>But if you want an alternative, that has effective luminance, then:</p> <pre><code> ColorMatrix colorMatrix = new ColorMatrix(new float[][]{ new float[]{ 0.3f, 0.3f, 0.3f,0,0}, new float[]{0.59f,0.59f,0.59f,0,0}, new float[]{0.11f,0.11f,0.11f,0,0}, new float[]{ 0, 0, 0,1,0,0}, new float[]{ 0, 0, 0,0,1,0}, new float[]{ 0, 0, 0,0,0,1}}); </code></pre> <h2>Edit 2: @Hans Passant.</h2> <p>Bitmap consists of pixels, that have color value <strong>RGBA</strong> {<strong>R</strong> ed, <strong>G</strong> reen, <strong>B</strong> lue, <strong>A</strong> lpha transparency}. To get grayscaled image from colored one, I multiply each pixel color value with my defined <code>colorMatrix</code>. </p> <p>Normal <a href="http://en.wikipedia.org/wiki/Matrix_multiplication" rel="nofollow noreferrer">2 matrix multiplying</a> speed is Θ(n^2), but this GDI+ linear conversion uses <a href="http://mathworld.wolfram.com/FastFourierTransform.html" rel="nofollow noreferrer">Fast Fourier Transform</a> to do it in Θ(n log(n)). This means for larger images, its vastly faster then other methods. </p> <p>Lets say I have input pixels <code>In</code>, with values <strong>{R, G, B, A}</strong> and I would like to get the formula for pixel values after matrix multiplication, and lets call it <code>Out</code> with values <strong>{A<sub>out</sub>, B<sub>out</sub>, C<sub>out</sub>, D<sub>out</sub>}</strong>.</p> <p><img src="https://i.stack.imgur.com/k9Xue.png" alt="enter image description here"></p> <p>Out:</p> <ul> <li>A<sub>out</sub> = r(4) A + r(3) B + r(2) G + r(1) R</li> <li>B<sub>out</sub> = g(4) A + g(3) B + g(2) G + g(1) R</li> <li>C<sub>out</sub> = b(4) A + b(3) B + b(2) G + b(1) R</li> <li>D<sub>out</sub> = a(4) A + a(3) B + a(2) G + a(1) R</li> </ul> <p>Or in this case:</p> <p><img src="https://i.stack.imgur.com/sKLMd.png" alt="enter image description here"></p> <pre><code>Out = { 0.11 B + 0.59 G + 0.3 R, 0.11 B + 0.59 G + 0.3 R, 0.11 B + 0.59 G + 0.3 R, A, 0, 0 } </code></pre> <p>Where formula of effective luminance of grayscale image is <code>0.11 blue + 0.59 green + 0.3 red</code>. So it's correct.</p>
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    2. CO0 down vote accept hi, but the problem is, that I dont have a .bmp in the beginning. I now the resolution and I have my greyscale values given in a ushort array. And from this I need to create a bitmap.
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