Subject: [ggl] Quick question about bg::difference
From: V D (zedxz2)
Date: 2011-10-25 20:30:13
Hi Barend,
This is great! Thank you very much.
Any idea if there is an upcoming stable snapshot of the trunk ?
-v
On Oct 25, 2011, at 1:18 PM, Barend Gehrels wrote:
> Hi,
>
> I believe that the difference problem you reported is fixed now. I'm avoiding now the reversal of arguments (both in difference and in sym_difference, which calls difference). It initially caused failing of one (of many) unit tests, but it appeared that that test was wrong. So thanks again for the report.
>
> I added unit tests for your cases.
>
> I just also tested your additional case below and it is now going OK as well, fixed by the earlier fix.
>
> I added also a unit test for this case. See the image below.
>
>
> On 25-10-2011 20:10, V D wrote:
>>
>> Hi Barend,
>>
>> Just a follow-up on this issue.
>>
>> Let's consider the case where MP and P are not disjoint.
>> bg::difference(MP, P) will lose any polygon in MP that is disjoint with P.
>>
>>
>> Example with images:
>>
>> Say the MP is the 2 squares below and P is the blue-ish rectangle.
>>
>> <Mail Attachment.png>
>>
>>
>>
>> The output should be something similar to:
>>
>> <Mail Attachment.png>
>>
>> But the actual output will be:
>>
>> <Mail Attachment.png>
>>
>>
>
>
> Images of P-Q and Q-P (I had this already so used other colors, purple is the output)
> <bebdfbja.png>
>
> BTW all these kind of images are created by the SVG extension which we think of moving to non-extension.
>
> Regards, Barend
>
>
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