How to avoid curved corners in rectangular patch element in matlab figure?

问题

When I generate a set of rectangular patches in a matlab figure, some of the rectangle edges are rendered curved or clipped rather than sharp, which is unwanted. This depends on the scale, zooming into the image tends to eliminate the effect. I thought this might have to do with an aliasing/compression effect. Curiously, using rectangle the problem seems to go away.

Here is an example of the problem at intermediate magnification (other problems such as dashed borders which shouldn't be there are also evident):

The code is from an answer to another question:

H=Hadamard(48); %# now to row-double the matrix 
A=(1+H)/2;
B=(1-H)/2;
C=[A; B]; %# the code below randomly permutes elements within the rows of the matrix 
[nRows,nCols] = size(C); 
[junk,idx] = sort(rand(nRows,nCols),2); %# convert column indices into linear indices 
idx = (idx-1)*nRows + ndgrid(1:nRows,1:nCols); %# rearrange whatever matrix 
E = C; 
E(:) = E(idx);
[X Y] = find(logical(E));
xl = length(X);
yl = length(Y);
figure, hold on
for ii=1:xl
     patch(X(ii) + [0 0 1 1],Y(ii) + [0.15 0.9 0.9 0.1],[1 1 1],'Edgecolor',[1 1 1])
end
axis([0 max(X)+1 0 max(Y)+1])
axis('square')
set(gca,'color',[0 0 0])
set(gca,'XTickLabel',[],'YTickLabel',[],'XTick',[],'YTick',[])

My questions are: (1) Is it possible (and how) to get rid of the curved corners and other glitches of patch objects seen in the example shown, at low to intermediate degrees of magnification used to display the entire figure on screen. (2) Most important is to be able to generate an image file (jpg, png, pdf...) which lacks the curved corners. All formats I looked into appear to conserve the unwanted effect. Answering 2 makes answering (1) essentially unimportant, and answering (1) presumably solves (2).

Edit

Since the problem goes away when rectangle is used, this appears to be a problem with the matlab rendering engine? Note: the example was generated with R14 but the OP of the question linked to had similar problems (matlab version unknown).

I went through the various lighting and edge representation options available for patch objects but no improvement was observed.

回答1:

The question is a likely repeat, for instance a similar questions was asked here.

The answer appears to be to avoid explicit use of patch when drawing rectangles. Use either fill or just rectangle instead. The following ways of generating the figure provide nearly equivalent results, as far as I could tell:

load had.mat % <-- load the data containing the matrix of interest in array E
[X Y] = find(logical(E));
xl = length(X);
yl = length(Y);
figure, hold on
for ii=1:xl
      rectangle('Position',[X(ii) Y(ii)+.2 1 0.8],'facecolor',[1 1 1],'edgecolor',[1 1 1])
%     fill([X(ii) X(ii) X(ii)+1 X(ii)+1], [Y(ii)+0.2 Y(ii)+0.8 Y(ii)+0.8 Y(ii)+0.2],[1 1 1],'edgecolor',[1 1 1],'marker','.','markersize',1)
end
set(gca,'color',[0 0 0])
set(gca,'XTickLabel',[],'YTickLabel',[],'XTick',[],'YTick',[])
set(gcf,'Renderer','zbuffer')

来源：https://stackoverflow.com/questions/18067304/how-to-avoid-curved-corners-in-rectangular-patch-element-in-matlab-figure

标签

matlab

graphics

rendering