% SL Script to filter text by color in PDF
% PStill 1.72.7+ needed to run
%
% You can define 'intercept' functions here:
% interceptShow()   -   is called for each text processed
% interceptFill()   -   is called for each fill processed
% interceptStroke()   -   is called for each stroke processed
% interceptImage()   -   is called for each image (mask) processed
%
% We are using only interceptShow here, for we are only interested in text for now

define interceptShow() {

	variable colorspace;
	variable cyan, yellow, magenta, black;
	
	% logprint("Calling interceptShow\n");
	
	% get the current colorspace, return values are
	% GRAY     == 1
	% RGB/HSB  == 2
	% CMYK     == 3
	% INDEXED  == 4
	% SPOT     == 5
	% PATTERN  == 6
	% DEVICEN  == 7
	
	colorspace = currentColorspace();
	
	% logprintint(colorspace);
	
	% get the current color as CMYK
	
	(cyan,magenta,yellow,black) = currentCMYKColor();
	
	if (colorspace < 4) {  	 % we process only plain DEVICEGRAY,RGB and CMYK Colorspaces
		
		% INFO: uncomment next line for debug color output as CMYK
		% logprint(sprintf("%f %f %f %f",cyan,magenta,yellow,black,4));

		% looking for a color of cyan 0 magenta 0.01 yellow 0.02 black 0.58
		
		if ((black > 0.57 and black < 0.59) and 
		    (cyan == 0.0) and 
        (magenta > 0.0 and magenta < 0.03) and 
		    (yellow > 0.01 and yellow < 0.03)) {	
		      % text in matching color, now convert to pure white
		    	setRGBColor(1.0,1.0,1.0);
		}
	}
}