[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: imread (repost)
From: |
Søren Hauberg |
Subject: |
Re: imread (repost) |
Date: |
Tue, 05 Aug 2008 06:53:26 +0200 |
man, 04 08 2008 kl. 21:57 -0400, skrev Thomas L. Scofield
> At least some png image files (BMP and PSD files as well, I believe)
> use 4 channels: red, green, blue and alpha. For those files, imread
> returns an array A satisfying size (A, 3) = 4.. (Would it do so as
> well for files using CMYK color space?) As such, the matrix A in
> which the image is stored cannot be sent off to imshow without
> limiting its 3rd coordinate, as in imshow (A(:, :, 1:3)). The changes
> John Eaton made to imread.m as I submitted it were quite necessary,
> but in the process code I had included for limiting this 3rd
> coordinate in imread before ever returning the image was lost. Should
> it be reinstated? Or, should imshow be modified to handle the
> occasional image like these png files? I don't mind making the
> changes, but lean towards altering imshow instead of imread if this
> doesn't result in an unacceptable incompatability with Matlab.
> Interestingly, when I read this same kind of png into Matlab, it
> returns a 2D matrix, not 3 like in Octave and, subsequently, it
> displays the image as grayscale when it was really a color image (the
> Octave call imshow(A(:, :, 1:3)) gets the color right). (Perhaps that
> is remedied in Matlab with optional arguments to imread.)
The matlab version of imread supports an extra output argument that
contains the alpha channel of an image. I don't think it is trivial (nor
a good idea) to change imshow to make it possible to show images with an
alpha channel. I mean, what should be to visual result when showing an
image that s 100% transparent? I'd stick with showing RGB only.
Søren
>
- imread (repost), Thomas L. Scofield, 2008/08/04
- Re: imread (repost),
Søren Hauberg <=
- Re: imread (repost), Thomas L. Scofield, 2008/08/05
- Re: imread (repost), Søren Hauberg, 2008/08/05
- Re: imread (repost), Søren Hauberg, 2008/08/05
- Re: imread (repost), Thomas L. Scofield, 2008/08/05
- Re: imread (repost), John W. Eaton, 2008/08/05
- Re: imread (repost), Thomas L. Scofield, 2008/08/05
- Re: imread (repost), John W. Eaton, 2008/08/05
- Re: imread (repost), John W. Eaton, 2008/08/06
- Re: imread (repost), Thomas L. Scofield, 2008/08/06
- Re: imread (repost), John W. Eaton, 2008/08/06