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Re: Image aspect ratio
From: |
Ben Abbott |
Subject: |
Re: Image aspect ratio |
Date: |
Sun, 14 Aug 2011 15:04:23 -0400 |
On Aug 14, 2011, at 4:40 AM, Divakar Ramachandran wrote:
> On Saturday 13 August 2011 08:23 PM, Ben Abbott wrote:
>> On Aug 13, 2011, at 9:00 AM, Divakar Ramachandran wrote:
>>
>>
>>> I am using Octave 3.2.4 on Microsoft Windows 7.
>>>
>>> A = imread("A8.tif");
>>>
>>> followed by
>>>
>>> imshow(A) or imagesc(A)
>>>
>>> results in a Gnuplot window that displays the image stretched along x-axis.
>>> axis("square") or axis("image") improves the aspect ratio slightly, but not
>>> to 1:1 that I require.
>>>
>>> Is there any workaround for this?
>>>
>>> Thanks in advance,
>>> Divakar
>>>
>> My initial thought is that your image isn't square. What is its size ?
>>
>> size (A)
>>
>>
> The image is square, 1024 x 1024 pixels:
>
>> octave-3.2.4.exe:388>INFO = imfinfo("A8_1.tif")
>> INFO =
>> {
>> Filename = C:\Users\divakar\Documents\A8_1.tif
>> FileSize = 1048784
>> Height = 1024
>> Width = 1024
>> BitDepth = 8
>
>
>> Another possibility is that your display has a different number of pixels
>> per inch in the horizontal and vertical directions? (this is rather rare).
>>
>> If you type the commands below ...
>>
>> imshow (A)
>> axis on
>>
>> ... and then measure the physical size of the axes box, what does the
>> following return?
>>
>> dpi = [diff(get(gca,"xlim")), diff(get(gca,"ylim"))] ./
>> [axis_box_width, axis_box_height]
>>
>> ... where axis_box_width and axis_box_height are the physical sizes of the
>> plot.
>
> This seems true in my case on the Dell Inspiron 580 desktop running Win 7 Pro
> 64-bit:
>
>> octave-3.2.4.exe:386>imshow(A)
>> octave-3.2.4.exe:377>axis("square")
>> octave-3.2.4.exe:381>dpi = [diff(get(gca,"xlim")), diff(get(gca,"ylim"))] ./
>> [18, 11.2]
>> dpi =
>>
>> 56.833 91.339
>>
>> octave-3.2.4.exe:379>
>
> Is there a workaround for this? Maybe a display property I can set somewhere
> and invoke through startup.m? I have also tried drawing circles using
> SmallBasic - these look fine. Somehow, the display geometry is not being
> sensed in Octave.
>
> I do not have this problem on Octave 3.2.3 installed on my laptop running
> Ubuntu 10.04 LTS 64-bit.
This looks like a bug to me. If you're inclined please file a bug report.
https://savannah.gnu.org/bugs/?group=octave
As a work around, you can try to modify the dataaspectratio
set (gca, "dataaspectratio", [56.833 91.339 91.339])
If that doesn't give the result you are looking for, please attach a picture of
what you see when you try that.
Ben