透明Png黑白图片上色（重新着色、改变成指定颜色）

场景：有时，我们需要给透明Png黑白图片改变成指定颜色（上色）。

前提：我们已经做好了带透明通道的PNG图片。

益处：使用此方法，只需要制作一张透明的黑色PNG图片即可，我们需要不同颜色的同样式图片时，直接使用本程序LOAD一个。

话不多说，直接上代码：

public static Bitmap ChangePngColor(string pngFileName, Color destColor)
        {
            Bitmap curBitmap = (Bitmap)Image.FromFile(pngFileName);
            if (curBitmap != null)
            {
                Rectangle rect = new Rectangle(0, 0, curBitmap.Width, curBitmap.Height);
                BitmapData bmpData = curBitmap.LockBits(rect, ImageLockMode.ReadWrite, curBitmap.PixelFormat);
                int c = curBitmap.PixelFormat == PixelFormat.Format32bppArgb ? 4 : 3;
                IntPtr ptr = bmpData.Scan0;
                int numBytes = bmpData.Stride * curBitmap.Height;
                byte[] rgbValues = new byte[numBytes];
                Marshal.Copy(ptr, rgbValues, 0, numBytes);
                for (int counter = 0; counter < rgbValues.Length; counter += c)
                {
                    if (c == 3)
                    {
                        if (rgbValues[counter] != destColor.R &&
                            rgbValues[counter + 1] != destColor.G &&
                            rgbValues[counter + 2] != destColor.B)
                        {
                            rgbValues[counter] = destColor.R;
                            rgbValues[counter + 1] = destColor.G;
                            rgbValues[counter + 2] = destColor.B;
                        }
                    }
                    else if (c == 4)
                    {
                        if (rgbValues[counter + 3] > 128 && rgbValues[counter] < 20)
                        {
                            rgbValues[counter] = destColor.B;
                            rgbValues[counter + 1] = destColor.G;
                            rgbValues[counter + 2] = destColor.R;
                            rgbValues[counter + 3] = destColor.A;
                        }
                    }
                }
                Marshal.Copy(rgbValues, 0, ptr, numBytes);
                curBitmap.UnlockBits(bmpData);
            }
            return curBitmap;
        }

调用方法：

   

private void menuItemPngToColorImage_Click(object sender, EventArgs e)
         {
             Color destColor = Color.FromArgb(255, Color.Red);
             string pngFileName = @"XXX.png";
             Bitmap curBitmap = ChangePngColor(pngFileName, destColor);
             using (Graphics gg = this.CreateGraphics())
             {
                 gg.Clear(Color.White);
                 gg.SmoothingMode = SmoothingMode.HighQuality;
                 gg.DrawImage(curBitmap, 0, 0, curBitmap.Width, curBitmap.Height);             
             }
         }

原图：

 改变颜色后的图片：

 注意：为了加快速度，需要允许不安全代码。

另：

也可以采用类似如下代码：

public static Bitmap ReplaceColor(string photoFileName, Color oldColor, Color newColor)
{
  Bitmap result=new Bitmap(1,1);
  using (Bitmap bmp = new Bitmap(@photoFileName))
  {
    result=new Bitmap(bmp.Width,bmp.Height);
    Graphics g = Graphics.FromImage(result);
    g.CompositingQuality = CompositingQuality.HighQuality;
    g.InterpolationMode = InterpolationMode.HighQualityBicubic;
    g.SmoothingMode = SmoothingMode.HighQuality;
    ColorMap[] colorMap = new ColorMap[1];
    colorMap[0] = new ColorMap();
    colorMap[0].OldColor = oldColor;
    colorMap[0].NewColor = newColor;
    ImageAttributes attr = new ImageAttributes();
    attr.SetRemapTable(colorMap);
    Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);        
    g.DrawImage(bmp, rect, 0, 0, rect.Width, rect.Height, g.PageUnit, attr);
  }
  return result;
}