[gdal-dev] creating overview image wit gdaladdo

[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,
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