How to change the color of a pixel use Magick.NET?

Question

How to change pixel color on the image use the lib Magick.NET. I use the following code:

MagickImage img = new MagickImage(@"d:\TEST\110706M01000509.jpg");
WritablePixelCollection pc = img.GetWritablePixels(100, 100, 50, 50);

foreach (Pixel p in pc)
{
    p.SetChannel(0, 255);
    p.SetChannel(1, 0);
    p.SetChannel(2, 0);
}

pc.Write();

img.Write(@"d:\TEST\110706M01000509_.jpg");

But on the output image the color of the pixels no red.

Example:

Why the color of figures is not red?

Answer 1

In 7.4, the above answers are largely correct, but, the method for getting the pixels is now

magick.GetPixels()

not

magick.GetWritablePixels()

They return IPixelCollection

Answer 2

With the current version of Magick.NET (7.0.0.0014) you will need to do this:

using (WritablePixelCollection pc = img.GetWritablePixels(100, 100, 50, 50))
{
  foreach (Pixel p in pc)
  {
    p.SetChannel(0, 255);
    p.SetChannel(1, 0);
    p.SetChannel(2, 0);
    pc.Set(p) // This will update the PixelCollection
  }
}

With Magick.NET 7.0.0.0015 the call to pc.Set will be done automatically and your example above will work.