Replace color operation is used to replace a color with another color. E.g. you can replace white color with transparency or replace transparency with red color.
Add Replace color operation:
“Replace color” list is used to specify the color to be replaced. Available values are transparency, black color, white color. If any other color is needed, select User defined line and choose the needed color from the dialog box that appears. “With color” list is used to specify the color which will replace the color selected in “Replace color” list.
“With tolerance” option is used to specify precision of the source color. Besides replacing one color, you can specify color precision with the help of “with tolerance” option. If its value is set to 0, only one precise color will be replaced. if the value is increased, the precise color will be replaced together with its neighboring gradations in accordance with the value specified in percent.
“Smoothing” flag is used to specify color replacement algorithm. If it is unchecked, only corresponding pixels will be replaced. If it is checked, first the corresponding pixels will be replaced and then borders of modified areas will be blurred.