Resizing with IrfanView

ASCII wrote:
>Dudley Hanks wrote:
>>I've noticed that, when cropping pics with IrfanView, strange
>>things can happen.
>>
>>For instance, when set to crop to a specific dimension, like 3000
>>x 2400, the end result isn't usually what is asked
>>for.
>>
>>In my latest pic, Winter Night, I tried cropping the pic to those
>>dimensions, but IrfanView kept cropping to 3001 x 2400. So I had
>>to get a sighted person to crop the pic in Adobe for
>>me.
>>
>>Is this a nag feature in the software? Or is there some other
>>reason for this behaviour?
>>
>>Take Care,
>>Dudley
>
>Do a [ctrl+r] to get to the resize field and see if the box to
>preserve aspect ratio is checked, toggle [alt+a] to clear it.
>

I haven't noticed it so much when doing a straight resize of a
whole image, as I'm not looking for a specific size in that
case, usually just cutting the pic down to a small enough size
to post on the net.

Rather, it's when I want a specific dimension, like an 8 x 10
at 300 dpi.

I tend to crop using the "Create Custom Selection" menu item,
and then throwing away everything outside the selection.


For the Winter Night pic, I had checked the use 5 x 4 aspect
ratio, which should have given me a straight 3000 x 2400 image.
Instead, it opted for 3001 x 2400. Even after redoing the
selection from differing starting points, the result was
always the same.

Of course, I found this a bit strange.

Take Care,
Dudley
 >> Stay informed about: Resizing with IrfanView 

Dudley Hanks wrote:
> I've noticed that, when cropping pics with IrfanView, strange
> things can happen.
>
> For instance, when set to crop to a specific dimension, like 3000
> x 2400, the end result isn't usually what is asked
> for.
>
> In my latest pic, Winter Night, I tried cropping the pic to those
> dimensions, but IrfanView kept cropping to 3001 x 2400.

I think I've had that problem too, I sometimes batch process for time
lapse video and it'll occasionally do that when resizing as well, which
breaks the ability of VirtualDub to make a single AVI from the results.
If you have a specific example, email them and maybe they'll fix it.

I suspect it's a rounding error.


> So I had
> to get a sighted person to crop the pic in Adobe for
> me.
>
> Is this a nag feature in the software? Or is there some other
> reason for this behaviour?
>
> Take Care,
> Dudley
 >> Stay informed about: Resizing with IrfanView 

On Tue, 15 Mar 2011 17:49:05 -0500, Dudley Hanks
wrote:
: ASCII wrote:
: >Dudley Hanks wrote:
: >>I've noticed that, when cropping pics with IrfanView, strange
: >>things can happen.
: >>
: >>For instance, when set to crop to a specific dimension, like 3000
: >>x 2400, the end result isn't usually what is asked
: >>for.
: >>
: >>In my latest pic, Winter Night, I tried cropping the pic to those
: >>dimensions, but IrfanView kept cropping to 3001 x 2400. So I had
: >>to get a sighted person to crop the pic in Adobe for
: >>me.
: >>
: >>Is this a nag feature in the software? Or is there some other
: >>reason for this behaviour?
: >>
: >>Take Care,
: >>Dudley
: >
: >Do a [ctrl+r] to get to the resize field and see if the box to
: >preserve aspect ratio is checked, toggle [alt+a] to clear it.
: >
:
: I haven't noticed it so much when doing a straight resize of a
: whole image, as I'm not looking for a specific size in that
: case, usually just cutting the pic down to a small enough size
: to post on the net.
:
: Rather, it's when I want a specific dimension, like an 8 x 10
: at 300 dpi.
:
: I tend to crop using the "Create Custom Selection" menu item,
: and then throwing away everything outside the selection.
:
:
: For the Winter Night pic, I had checked the use 5 x 4 aspect
: ratio, which should have given me a straight 3000 x 2400 image.
: Instead, it opted for 3001 x 2400. Even after redoing the
: selection from differing starting points, the result was
: always the same.
:
: Of course, I found this a bit strange.

The roundoff error probably occurs when the program tries to convert inches to
pixels. If you specify the dimensions in pixels instead of inches, the error
shouldn't occur. Or you can specify the aspect ratio and one dimension, but
make sure that you choose a value (in pixels) for that dimension that will
result in the other dimension also having an integral number of pixels.

Bob
 >> Stay informed about: Resizing with IrfanView