is to define a RemapTable
ColorMap colorMap = new ColorMap();
//My watermark was defined with a background of 100% Green this will
//be the color we search for and replace with transparency
colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);
colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);
ColorMap[] remapTable = {colorMap};
imageAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);
//The second color manipulation is used to change the opacity of the
//watermark. This is done by applying a 5x5 matrix that contains the
//coordinates for the RGBA space. By setting the 3rd row and 3rd column
//to 0.3f we achive a level of opacity
float[][] colorMatrixElements = {
new float[] {1.0f, 0.0f, 0.0f, 0.0f, 0.0f},
new float[] {0.0f, 1.0f, 0.0f, 0.0f, 0.0f},
new float[] {0.0f, 0.0f, 1.0f, 0.0f, 0.0f},
new float[] {0.0f, 0.0f, 0.0f, 0.3f, 0.0f},
new float[] {0.0f, 0.0f, 0.0f, 0.0f, 1.0f}};
ColorMatrix wmColorMatrix = new ColorMatrix(colorMatrixElements);
imageAtt
