imresize incorrectly clips output to [0,1]

[Stefan Gustavson]

Bug report for Octave 3.0.3 configured for i686-pc-msdosmsvc

Description:
-----------

The function imresize(img, [w h], interp), when using double input,
incorrectly clips its output to the range [0,1]. This is both wrong and
inconsistent with what Matlab does. Many image processing applications
use a wider range of values than [0,1]. Negative values are only to be
disallowed in images representing pictures, and even those have no
inherent upper limit. Clipping to a certain range is an issue with image
file formats with a limited precision and range (e.g. 8-bit samples),
not with the image data as such.

If arbitrary clipping to [0,1] is performed for any other image
processing functions, they need to be fixed as well. I am sorry,
but I have not found the time to check the entire "image" package.

Repeat-By:
---------

img = 10*(rand([64, 64])-0.5); % Range of img is [-5, 5]
img2 = imresize(img, [64, 64]); % Essentially a no-op
% Range of img2 is clipped to [0,1], as demonstrated by:
min(img2(:))
max(img2(:))

Fix:
---

Remove the three lines marked with "->" from "imremap.m":

  ## Change the class of the results according to the class of the image
  c = class(im);
  if (strcmpi(c, "double"))
->    ## Remove overshooting caused by bicubic interpolation
->   warped(warped>1) = 1;
->   warped(warped<0) = 0;
  elseif (strcmpi(c, "uint8"))
    warped = uint8(warped);
  elseif (strcmpi(c, "uint16"))
    warped = uint16(warped);
  endif


Configuration (please do not edit this section):
-----------------------------------------------

uname output: Windows
configure opts:
Fortran compiler: fc-msvc
FFLAGS: -O2
F2C: @F2C@
F2CFLAGS: @F2CFLAGS@
FLIBS: -lhdf5 -lzlib -lf2c -lkernel32
CPPFLAGS: -I. -Ic:/Software/VCLibs/include
INCFLAGS: -I. -I. -I./liboctave -I./src -I./libcruft/misc
C compiler: cc-msvc, version
CFLAGS: -O2 -MD
CPICFLAG:
C++ compiler: cc-msvc, version
CXXFLAGS: -O2 -EHs -MD
CXXPICFLAG:
LD_CXX: cc-msvc
LDFLAGS:
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RLD_FLAG:
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