Thread Subject: Wavelet Color Conversion

Hi,
I want to do an image compression. I use the function:

      [xcCOIF,cxc,lxc,perf0,perfl2 = wdencmp
('gbl',c,s,'coif1',level,thr,'h',1);

and after:

                     image(xcCOIF);

to show the image. The problem is that all the colors are
changed at the display. The same problem for Daubechies or
Biorthogonal wavelets.

Why it changes the color? How can I fix it?

"Jonathan Garzon" <jonathangarzon@gmail.com> wrote in message
<flbadd$loj$1@fred.mathworks.com>...
> Hi,
> I want to do an image compression. I use the function:
>
> [xcCOIF,cxc,lxc,perf0,perfl2 = wdencmp
> ('gbl',c,s,'coif1',level,thr,'h',1);
>
> and after:
>
> image(xcCOIF);
>
> to show the image. The problem is that all the colors are
> changed at the display. The same problem for Daubechies or
> Biorthogonal wavelets.
>
> Why it changes the color? How can I fix it?
The reason is that you compress separatedly three color bands
(RGB). You should change to YUV color model or some other color
decorrelation techniques.

Anh Huy Phan
RIKEN - BSI

Another approach you can try is to convert the rgb image into an index image and a colormap. Do the wavelet compression or whatever on the index image and after reconstruction when you display the image, use imshow command with the colormap option.

Yumnam Kirani Singh <kirani.singh@gmail.com> wrote in
message
<64671.1199165103959.JavaMail.jakarta@nitrogen.mathforum.org>...
> Another approach you can try is to convert the rgb image
into an index image and a colormap. Do the wavelet
compression or whatever on the index image and after
reconstruction when you display the image, use imshow
command with the colormap option.


Hi,
Firs of all, thank you for helping.
I try to separate the index and the colormap, but it gives
me a problem with the input parameters.

I´m still with the same problem. Maybe you have another
option or know how to fix it. (reminder: undesirable color
from a png, gif image after wavelet).

Thank you again, Jonathan