(3.48) Fixed -transparency color artifacts, set default bgcolor tolerance of +-0.1 (issue #400)

Author: altmany

export_fig.m

@@ -117,9 +117,12 @@
 %   -transparent=<color> convert all pixels in the specified color (RGB tripplet
 %             or a Matlab predefined color string e.g. 'r'). Usage examples:
 %             -transparent=g or -transparent=[1,.5,.2] or -transparent=80,65,235
-%             Optional suffix +-<value> adds tolerance to pixels color matching
-%             for example: -transparent=g+-30 or -transparent=[1,.5,.2]+-0.1
-%             Note: only supported by PNG,GIF,TIF formats.
+%   -transparent=<color>+-<value> adds optional tolerance to bgcolor matching.
+%             For example: -transparent=g+-30 or -transparent=[1,.5,.2]+-0.1
+%             <color> may be omitted, e.g. -transparent+-8 or -transparent=+-.03
+%             Default tolerance is 0.1 (or 25 in [0,255] units), to reduce color
+%             artifacts around letters and line edges. Note: transparent color
+%             customization is only supported by PNG,GIF,TIF formats.
 %   -nocrop - option indicating that empty margins should not be cropped.
 %   -c[<val>,<val>,<val>,<val>] - option indicating crop amounts. Must be
 %             a 4-element vector of numeric values: [top,right,bottom,left]
@@ -406,6 +409,7 @@
 % 02/05/24: (3.45) Display the builtin error message when uifigure cannot be exported (issue #387); fixed contour labels with non-default FontName incorrectly exported as Courier (issue #388)
 % 09/05/24: (3.46) Added -xkcd option (thanks @slayton); added .fig input and output format (previously undocumented & buggy); redirect .tex output to matlab2tikz utility
 % 05/11/24: (3.47) Fixed -transparency in case the default bgcolor is already used in the figure (issue #398); enabled specifying non-default transparency color via -transparency parameter; suppress warnings about setting figure position; multiple -xkcd fixes
+% 06/03/25: (3.48) Fixed -transparency color artifacts, set default bgcolor tolerance of +-0.1 (issue #400)
 %}
 
     if nargout
@@ -443,7 +447,7 @@
     [fig, options] = parse_args(nargout, fig, argNames, varargin{:});
 
     % Check for newer version and exportgraphics/copygraphics compatibility
-    currentVersion = 3.47;
+    currentVersion = 3.48;
     if options.version  % export_fig's version requested - return it and bail out
         imageData = currentVersion;
         return
@@ -1709,7 +1713,7 @@ function notify(filename)
         'crop_amounts',    nan(1,4), ...  % auto-crop all 4 image sides
         'transparent',     false, ...
         'tcol',            [], ...
-        'ttol',            0, ...
+        'ttol',            uint8(25), ... % in [0,255] RGB color units
         'renderer',        0, ...         % 0: default, 1: OpenGL, 2: ZBuffer, 3: Painters
         'pdf',             false, ...
         'eps',             false, ...
@@ -1791,7 +1795,7 @@ function notify(filename)
         else %if ischar(thisArg) && ~isempty(thisArg)
             if thisArg(1) == '-'
                 addToOptionsStr = true;
-                [thisArg,extra] = strtok(thisArg,'=');
+                [thisArg,extra] = strtok(thisArg,{'=','+'});
                 switch lower(thisArg(2:end))
                     case 'nocrop'
                         options.crop = false;
@@ -1816,11 +1820,18 @@ function notify(filename)
                                 options.tcol = defaultColors(colIdx,:);
                             else
                                 tcol = str2num(extra); %#ok<ST2NM>
-                                assert(isequal(size(tcol),[1,3]),'export_fig:invalid_tcol','Invalid transparent color %s specified',extra);
-                                if all(tcol <= 1) %fractional values
-                                    tcol = 255 * tcol; %[0-1] => [0-255]
+                                if numel(tcol)==1 && isempty(tol)
+                                    if tcol <= 1 %fractional value
+                                        tcol = 255 * tcol; %[0-1] => [0-255]
+                                    end
+                                    options.ttol = uint8(tcol);
+                                else
+                                    assert(isequal(size(tcol),[1,3]),'export_fig:invalid_tcol','Invalid transparent color %s specified',extra);
+                                    if all(tcol <= 1) %fractional values
+                                        tcol = 255 * tcol; %[0-1] => [0-255]
+                                    end
+                                    options.tcol = uint8(tcol);
                                 end
-                                options.tcol = uint8(tcol);
                             end
                             if length(tol) > 2
                                 tol = tol(3:end);  % discard '+-'
@@ -2400,12 +2411,14 @@ function eps_remove_background(fname, count)
     if options.transparent
         % Modify the figure's bgcolor to off-white
         if isempty(options.tcol)
-            bgcol = uint8(254*[1,1,1]);  %default bgcolor =off-white
+            bgcol = uint8([255,255,254]);  %default bgcolor =off-white
+            white = uint8([255,255,255]);
 
             % Determine off-white shade not already used in the fig - issue #398
             A = getFigImage2(fig, magnify, renderer, options);  % get RGB tripplets
-            A = unique(reshape(A,[],3),'rows');    % reshape [m,n,3] => [m*n,3]
-            A = sum(double(A).*(256.^[2,1,0]),2);  % convert RGB tripplets => int
+            A = reshape(A,[],3);    % reshape [m,n,3] => [m*n,3]
+            A = unique([A; white], 'rows'); % add pure white  %issue #400
+            A = sort(sum(double(A).*(256.^[2,1,0]),2)); % convert RGB tripplets => int
             d = A(find(diff(A)>1,1,'last')+1) - 1; %=largest RGB value -1 (off-white)
             if ~isempty(d)
                 n=2; while n>=0, p=256^n; bgcol(3-n)=floor(d/p); d=rem(d,p); n=n-1; end %int => RGB tripplet