From octave-maintainers-request at bevo dot che dot wisc dot edu Wed Mar 10 01:10:19 2004
Subject: Re: imread image sizing
From: JD Cole <listguy at transientresearch dot com>
To: Ross Vandegrift <ross at willow dot seitz dot com>
CC: help-octave at bevo dot che dot wisc dot edu, octave-maintainers@bevo.che.wisc.edu
Date: Tue, 09 Mar 2004 23:40:22 -0800

Hi Ross,
    I've come across this before too. If you follow the trail of 
functions that 'imshow' actually uses, you'd see that after it creates a 
colormap and an indexed image from the r/g/b parameters, it uses the 
'image' command to display them. 'image' takes  a scale parameter, but 
in this case, imshow doesn't pass one, in the case of no scale 
parameter, 'image' decides to make a scaled image, hence, your 320x240. 
You got a couple of choices, you could create you're own version of 
'imshow' and add a scale parameter, something like this

imshow (a1, a2, a3, scale)
....
....
image (a1, scale)
....
....
or at the very least

....
image (a1, 1)
....

This problem bothers me often too, but I'm not sure what the mainstream 
solution would be since changing the definition for 'imshow', as 
distributed with octave, would break from compatibility with other 
numerical programs which shall remain un-named.

Maintainers have any thoughts?

JD
Ross Vandegrift wrote:

>Hello everyone,
>
>	I'm working on an image analysis project, and am using imread to
>read in a color 640x480 JPEG file and sample some points.
>
>	Oddly though, when read in and displayed, the graphic is
>displayed as 320x240.  If I manually run "display eye.jpg", the image is
>loaded as 640x480.  I've tried setting "-size 640x480" and "-sample
>640x480" in the options, neither one helps.
>
>	Here's how I'm loading/displaying my image:
>
>[red, green, blue] = imread('jpg:eye.jpg', ["-size 640x480";]);
>red = red / 255;
>blue = blue / 255;
>green = green / 255;
>imshow(red, green, blue)
>
>	It's not a critical problem or anything - I'm still able to work
>on the project at 320x240, but is there something I can do to get
>640x480?
>
>Thanks!
>  
>