Swaps the alpha and value channels of a monochrome image. Transparent areas become black, and black areas become transparent. - CSharp System.Drawing

CSharp examples for System.Drawing:Bitmap

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Description

Swaps the alpha and value channels of a monochrome image. Transparent areas become black, and black areas become transparent.

Demo Code


using System.Windows.Forms;
using System.Text;
using System.Linq;
using System.Drawing;
using System.Collections.Generic;
using System;//  w ww  .j a va 2s .co  m

public class Main{
        /// <summary>
      /// Swaps the alpha and value channels of a monochrome image. Transparent areas become black, and black areas become transparent.
      /// </summary>
      public static Bitmap AlphaSwap(Bitmap source) {
         Color c;
         if (IsSolidColor(source, out c) && c.A == 0) {
            // fully transparent image
            return source;
         }
         Bitmap ret = new Bitmap(source.Width, source.Height);
         for (int x = 0; x < ret.Width; x++) {
            for (int y = 0; y < ret.Height; y++) {
               Color fromColor = source.GetPixel(x, y);
               int toColor = fromColor.A == 0 ? -0x01000000 : fromColor.A * 0x10101 + fromColor.R * 0x1000000;
               ret.SetPixel(x, y, Color.FromArgb(toColor));
            }
         }
         return ret;
      }
        /// <summary>
      /// Checks if the given bitmap is a single color. If the result is true, its color will be stored in the second parameter.
      /// </summary>
      public static bool IsSolidColor(Bitmap bmp, out Color c) {
         c = bmp.GetPixel(0, 0);
         for (int y = 0; y < bmp.Height; y++) {
            for (int x = 0; x < bmp.Width; x++) {
               if (bmp.GetPixel(x, y) != c) {
                  return false;
               }
            }
         }
         return true;
      }
}

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