[37] | 1 | function J = imdown(I,method) |
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| 2 | % IMDOWN Downsample image |
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| 3 | % J = IMDOWN(I,'sample') downsamples the image I by half by |
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| 4 | % discarding each other pixel. |
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| 5 | % |
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| 6 | % IMDOWN(I,'avg') downsmples by averaging groups of four pixels. |
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| 7 | % |
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| 8 | % The image is always converted to double format. |
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| 9 | % |
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| 10 | % See also IMUP(). |
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| 11 | |
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| 12 | % AUTORIGHTS |
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| 13 | % Copyright (C) 2006 Andrea Vedaldi |
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| 14 | % |
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| 15 | % This file is part of VLUtil. |
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| 16 | % |
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| 17 | % VLUtil is free software; you can redistribute it and/or modify |
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| 18 | % it under the terms of the GNU General Public License as published by |
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| 19 | % the Free Software Foundation; either version 2, or (at your option) |
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| 20 | % any later version. |
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| 21 | % |
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| 22 | % This program is distributed in the hope that it will be useful, |
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| 23 | % but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 24 | % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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| 25 | % GNU General Public License for more details. |
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| 26 | % |
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| 27 | % You should have received a copy of the GNU General Public License |
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| 28 | % along with this program; if not, write to the Free Software Foundation, |
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| 29 | % Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
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| 30 | |
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| 31 | I = rgb2double(I) ; |
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| 32 | |
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| 33 | if nargin < 2 |
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| 34 | method = 'sample' ; |
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| 35 | end |
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| 36 | |
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| 37 | switch method |
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| 38 | case 'sample' |
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| 39 | J = I(1:2:end,1:2:end,:) ; |
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| 40 | |
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| 41 | case 'avg' |
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| 42 | J = ... |
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| 43 | I(1:2:end-1,1:2:end-1,:) + ... |
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| 44 | I(2:2:end,1:2:end-1,:) + ... |
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| 45 | I(1:2:end-1,2:2:end,:) + ... |
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| 46 | I(2:2:end,2:2:end,:) ; |
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| 47 | J = J / 4 ; |
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| 48 | end |
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