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- % [ZOOM] = pixelAxes(DIMS, ZOOM)
- %
- % Set the axes of the current plot to cover a multiple of DIMS pixels,
- % thereby eliminating screen aliasing artifacts when displaying an
- % image of size DIMS.
- %
- % ZOOM (optional, default='same') expresses the desired number of
- % samples displayed per screen pixel. It should be a scalar, which
- % will be rounded to the nearest integer, or 1 over an integer. It
- % may also be the string 'same' or 'auto', in which case the value is chosen so
- % as to produce an image closest in size to the currently displayed
- % image. It may also be the string 'full', in which case the image is
- % made as large as possible while still fitting in the window.
- % Eero Simoncelli, 2/97.
- function [zoom] = pixelAxes(dims, zoom)
- %------------------------------------------------------------
- %% OPTIONAL ARGS:
- if (exist('zoom') ~= 1)
- zoom = 'same';
- end
- %% Reverse dimension order, since Figure Positions reported as (x,y).
- dims = dims(2:-1:1);
- %% Use MatLab's axis function to force square pixels, etc:
- axis('image');
- ax = gca;
- oldunits = get(ax,'Units');
- if strcmp(zoom,'full');
- set(ax,'Units','normalized');
- set(ax,'Position',[0 0 1 1]);
- zoom = 'same';
- end
- set(ax,'Units','pixels');
- pos = get(ax,'Position');
- ctr = pos(1:2)+pos(3:4)/2;
- if (strcmp(zoom,'same') | strcmp(zoom,'auto'))
- %% HACK: enlarge slightly so that floor doesn't round down
- zoom = min( pos(3:4) ./ (dims - 1) );
- elseif isstr(zoom)
- error(sprintf('Bad ZOOM argument: %s',zoom));
- end
- %% Force zoom value to be an integer, or inverse integer.
- if (zoom < 0.75)
- zoom = 1/ceil(1/zoom);
- %% Round upward, subtracting 0.5 to avoid floating point errors.
- newsz = ceil(zoom*(dims-0.5));
- else
- zoom = floor(zoom + 0.001); % Avoid floating pt errors
- if (zoom < 1.5) % zoom=1
- zoom = 1;
- newsz = dims + 0.5;
- else
- newsz = zoom*(dims-1) + mod(zoom,2);
- end
- end
- set(ax,'Position', [floor(ctr-newsz/2)+0.5, newsz] )
- % Restore units
- set(ax,'Units',oldunits);
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