PanoTools:
blending with ImageMagick (was Re: monopod)
Geraldine Joffre 2006-Feb-25 12:25:11
--- In #removed#, Yuval Levy <yuval_levy@...> wrote:
>
> michael crane wrote:
> > Sometimes I use a .bat file to run "convert" on the bracketed exposures
> > but this is not always successful.
>
> you mean the "convert" command line from ImageMagick as in convert
> image1.tif image2.tif -average resultingimage.tif ?
>
> I've tried this quickly yesterday and compared it with a simple but highly
> effective way of exposure blending in photoshop (put the two exposures
> on top of each other and use the sliders in the layer blending options).
>
> Unsurprisingly, the result in Photoshop is much better, especially in the
> darker areas. I believe this is because of the mask that makes sure that
> the noise associated with the underexposed areas does not come
> through the end result, while the average is still affected by this noise.
That's only part of the reason. The purpose of a blending mask is to ensure
that the overexposed photo is used for the shadow areas and the
underexposed photo for the highlights. This has for effect of increasing the
reproduced dynamic range, and therefore produces a better looking result
than a simple averaging (which just averages every pixels the same way,
regardless of whether the pixel is in the highlights or the shadows).
> So my question is whether it is possible to replicate this photoshop
behaviour with imagemagick, i.e. create a blending mask in imagemagick ?
Based on the ImageMagick documentation, this seems to be possible with the
-composite operator
http://www.imagemagick.org/script/command-line-options.php?#composite
But I'm not sure I understand why you would prefer using a command line
program such as ImageMagick instead of Photomatix for that purpose? I
would be interested to know your reasons for that.
Averaging images is free in Photomatix and also exposure blending with the
combination method limited to two images. The Photomatix Basic freeware
offers both in batch mode too.
Geraldine Joffre
HDR Imaging for Photography
www.hdrsoft.com
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