[Digikam-users] Re: aspect ratio crop tool

[David Kerber]

On 5/16/2011 12:51 PM, Remco Viëtor wrote:
> on Monday 16 May 2011, David Kerber wrote:
>> On 5/16/2011 11:42 AM, Dan McDaniel wrote:
>>>
>>> I have noticed that very often the Aspect Ratio Crop Tool does not crop
>>> accurately, but will be off by pixel.  So, for example, if I want  a 5:4
>>> aspect ratio which should be 1.25 the crop will be off by a pixel and
>>> give a ratio of 1.2499 or such.
>>>
>>> This small difference does not affect the look of the image, but when I
>>> send it to the photo service to be printed the software detects that it
>>> is not in the correct ratio and each time I have to tell it that it's OK
>>> to crop the image.
>>>
>>> Has anyone else noticed this? I'm using 1.2.0 on Debian and 1.9.0 on
>>> Fedora and both exhibit this behavior.
>>>
>>
>> Are your originals' sizes such that 1.25 will give an exact pixel
>> result, and not have to be rounded either up or down to get to a whole
>> pixel?
>>
>
> the size of the original isn't important, the size of the crop is:
> if you take a length of 1003 pixels, there's no way you can get the 5:4 ratio
> exact on pixel level, as we only use whole pixels: you'd have to make the long
> edge either 1000 (giving 800 for the short side) or 1005 (804 for the short
> size).

Yes, true.  It looked to me like the OP was leaving on of the dimensions 
of his original image unchanged, and trying to crop only the other 
dimension.  That would work only if the original dimensions were such 
that a factor of multiplying or dividing by 1.25 would give an integer 
result.


> Already in 1.9.0 (and a few versions before iirc) there is the 'exact ratio'
> option, which indeed limits the sizes you can pick so that you get the exact
> ratio specified.

I didn't know that; it would be handy.