[XForms] subpixel sampling in image scaling - does it work?

[Michal Szymanski]

Hello,

I have a simple app displaying several images from a digital camera in
a 3x3 grid of small (230x170) canvases, with the main purpose of easy
choosing the images for hardcopy prints.

The original images are 1840x1232 JPEGs so before displaying I scale
them to the canvas' size. I have noticed that the quality of such
shrinked images is rather poor so I tried to employ subpixel sampling to
make them look better. Strangely, or-ing FLIMAGE_SUBPIXEL flag into the
basic flag used in flimage_scale(img[no], w, h, scale_flag) (which used
to be FLIMAGE_ASPECT | FLIMAGE_CENTER) DOES NOT change anything. When I
imported (ImageMagick's import) single image canvas into a TIFF image
file (first, with the flag added and then without it), the resulting two
files did not show ANY differences on byte-by-byte comparison (with the
one-byte exception at the file name which is also stored in a TIFF
image).

Any ideas what is wrong here? I can hardly imagine that a typical image
(two persons in a garden full of flowers) could yield no differences
after any pixel interpolation process.

regards, Michal.

-- 
  Michal Szymanski (msz at astrouw.edu.pl)
  Warsaw University Observatory, Warszawa, POLAND