Why does the GETFRAME function capture only the last object that was drawn in MATLAB 7.0 (R14)?

I have set the 'EraseMode' property of my figure to 'none' in order to retain points that I have already drawn. When I use the GETFRAME function to capture the image, only the last area that was drawn is captured. For example, try:

axis([0 10 0 10]);

% Set up a triangle patch with 'EraseMode' set to 'none'

V = [0 0 0; 0.5 1 0; 1 0 0];

F = [1 2 3];

p1 = patch('vertices',V,'faces',F,'EraseMode','none','facecolor','r');

% Make more triangles by moving the existing triangle

for i=1:10   

      set(p1,'vertices',V);

      drawnow;

      V = V+1;

end

% Now capture the image

im = getframe(gcf);

clf;

image(im.cdata);

set(gca,'position',[0 0 1 1])

I expect the image to include all of the triangle locations, as it appeared on the screen when GETFRAME is called, rather than containing only the last triangle.

Answer 1

[MathWorks Support Team]

We have verified that there is a bug in MATLAB 7.0 (R14) in the way that the GETFRAME function handles capturing figures when the 'EraseMode' property is set to 'none'.

To work around this issue, add successive objects to the image rather than placing only the most recent object in the figure and retaining the rest using the 'EraseMode' property, as shown in this modification of the example:

axis([0 10 0 10]);

% Set up a triangle patch with

% EraseMode set to None

V = [0 0 0; 0.5 1 0; 1 0 0];

F = [1 2 3];

p1 = patch('vertices',V,'faces',F,'facecolor','r');

hold on;

% Move the triangle around

for i=1:10   

      patch('vertices',V,'faces',F,'facecolor','r');

      drawnow;

      V = V+1;

end

% Now capture the image

im = getframe(gcf);

clf;

image(im.cdata);

set(gca,'position',[0 0 1 1])