[gdal-dev] creating overview image wit gdaladdo

[Toni Pignataro]

Hi Frank,

I still did not try it out, i will give feedback as soon i have tried it 
out. The image is like you mentioned an 1bit black and white image.

Thanks and regards,
Toni


Am 31.05.2011 15:53, schrieb Frank Warmerdam:
> On 11-05-31 09:29 AM, Toni Pignataro wrote:
>> Hello,
>>
>> I am trying to create an overview image with gdaladdo and tried out
>> different
>> resampling parameter. My results looks fine on large scale, but
>> zooming out
>> (small scale) the image looks really poor. What I want to to achieve or
>> reproduce is an effect like in ArcMap. Here embedding an black and
>> white image
>> and enabling the 'create Pyramids' option, it generates a really
>> smooth image
>> on small scale. Any idea or suggestion how to achieve this effect? Or
>> is this
>> an special ArcMap effect?
>
> Toni,
>
> Is your base image a 1bit black and white image? If so, you might want
> to try AVERAGE_BIT2GRAYSCALE as the resampling algorithm. This is a
> special algorithm (implemented for ArcGIS) that produces greyscale
> overviews
> for one 1bit black and white images. Note that not all applications will
> handle the situation of greyscale overviews on a 1 bit base image
> gracefully.
>
> Best regards,