CODEWITHSUNDEEP
c#bitmap
talsegal
talsegal

Reputation: 543

How to set and retrieve pixels from a Bitmap

Why is the following conditional failing?

brush = new Bitmap(10, 10);
brush.SetPixel(1, 1, Color.Black);
if (brush.GetPixel(1, 1) == Color.Black)
{          
    MessageBox.Show("hello");
}

// Will not show "hello"

Upvotes: 0

Views: 149

Answers (2)

Rudis
Rudis

Reputation: 1217

The == operator has following definition:

public static bool operator ==(Color left, Color right)
{
  if (left.value != right.value || (int) left.state != (int) right.state || (int) left.knownColor != (int) right.knownColor)
    return false;
  if (left.name == right.name)
    return true;
  if (left.name == null || right.name == null)
    return false;
  else
    return left.name.Equals(right.name);
}

If you look at Color.Black and result from GetPixel in debug mode you will see differences.

Upvotes: 0

Pierre-Luc Pineault
Pierre-Luc Pineault

Reputation: 9191

Your pixel is indeed black, but it seems to fail because Color.Black is a KnownColor and NamedColor while ff000000 (the result of your GetPixel) is not. You can change the condition to verify directly the ARGB values instead :

if (brush.GetPixel(1, 1).ToArgb() == Color.Black.ToArgb())
{          
    MessageBox.Show("hello");
}

Upvotes: 3

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