Question on Image > Scale

[Zhuo Wang-2]

Hi,

I was trying to use Image>Scale to downsample some autoradiographic images.
I set: X Scale = 0.5
        Y Scale = 0.5
        Interpolate unchecked
        Fill with Background Color unchecked
        Process Entire Stack checked
        Create New Window checked.

Could some one please explain to me what algorithm is used to scale the
image?  Averaging every four pixels into one?  Or sample one pixel out of
four?

Thanks in advance.

Sincerely,

Zhuo

[Wayne Rasband]

> I was trying to use Image>Scale to downsample some autoradiographic
> images.
> I set: X Scale = 0.5
>         Y Scale = 0.5
>         Interpolate unchecked
>         Fill with Background Color unchecked
>         Process Entire Stack checked
>         Create New Window checked.
>
> Could some one please explain to me what algorithm is used to scale the
> image?  Averaging every four pixels into one?  Or sample one pixel out
> of
> four?

It samples one pixel out of four. To create better looking thumbnails,
it does averaging if scale <= 0.25 and the image is in RGB format. The
averaging Reducer plugin
(http://rsb.info.nih.gov/ij/plugins/reducer.html) down sizes both
grayscale and RGB images using averaging.

-wayne