Creating a copy of a figure in a higher resolution is time consuming, because a lot of work has to be done. You can reduce the time required by print by writing to a SSD or RAM-disk. Which OS are you using?
Another way is using the undocumented hardcopy, which is the core function of print. hardcopy replies an RGB array, but it demands for some specific modifications of the figure - otherwise Matlab crashs. I give a short example, which works with Matlab 6.5, 7.8 and 7.13 without any guarantee:
ResolutionStr = sprintf('-r%d', round(Resolution));
% Prepare figure for hardcopy:
drawnow;
fig_Renderer = get(FigH, 'Renderer');
fig_Paperposmode = get(FigH, 'PaperPositionMode');
fig_PaperOrient = get(FigH, 'PaperOrientation');
fig_Invhardcopy = get(FigH, 'InvertHardcopy');
set(FigH, ...
'PaperPositionMode', 'auto', ...
'PaperOrientation', 'portrait', ...
'InvertHardcopy', 'off');
% Create hard copy in high resolution:
% Simulate PRINT command (save time for writing and reading image file):
% Set units of axes and text from PIXELS to POINTS to keep their sizes
% independent from from the output resolution:
% See: graphics/private/preparehg.m
root_SHH = get(0, 'ShowHiddenHandles');
set(0, 'ShowHiddenHandles', 'on');
text_axes_H = [findobj(FigH, 'Type', 'axes'); ...
findobj(FigH, 'Type', 'text')];
pixelObj = findobj(text_axes_H, 'Units', 'pixels');
fontPixelObj = findobj(text_axes_H, 'FontUnits', 'pixels');
set(pixelObj, 'Units', 'points');
set(fontPixelObj, 'FontUnits', 'points');
% Set image driver:
if strcmpi(fig_Renderer, 'painters')
imageDriver = '-dzbuffer';
else
imageDriver = ['-d', fig_Renderer];
end
fig_ResizeFcn = get(FigH, 'ResizeFcn');
set(FigH, 'ResizeFcn', '');
% "Normal" is the only erasemode, which can be rendered!
% See: NOANIMATE.
EraseModeH = findobj(FigH, 'EraseMode', 'normal', '-not');
EraseMode = get(EraseModeH, {'EraseMode'});
set(EraseModeH, 'EraseMode', 'normal');
% Get image as RGB array:
high = hardcopy(FigH, imageDriver, ResolutionStr);
% Restore units of axes and text objects, and EraseMode:
set(pixelObj, 'Units', 'pixels');
set(fontPixelObj, 'FontUnits', 'pixels');
set(EraseModeH, {'EraseMode'}, EraseMode);
set(0, 'ShowHiddenHandles', root_SHH);
set(FigH, 'ResizeFcn', fig_ResizeFcn);
