Legacy ImageMagick Discussions Archive

Hi,

I'm new to this forum, but I would like to know how I can use image magick to improve an sequence of images taken at night with a time lapse camera (Rasberry PI) so I can improve the overall quality of the video.

Thanks for your help.
Lionel

What don't you like about the quality? What do you want to improve? Adjusting levels or colour balance are two common needs. If you put up a sample image to somewhere like dropbox.com we can be more specific.

With images for a video, we generally want to adjust all the frames in the same way, so some features like "-auto-level" don't work well, but there are workarounds.

Here is the context:
I'm taking many pictures (with different shutter speed) every 5 min
at night I use a shutter speed of 5 sec and here are two sample picture:



note that I would like to process them with convert version
graphickmagick 1.3.21 2015-02-08 Q16

It says:

Sorry I changed it.

Here are my two samples
https://drive.google.com/open?id=0B0u3v ... HYtM2kzM2s
https://drive.google.com/open?id=0B0u3v ... UZaWVRSU2c

I don't see the -auto-level as an option in convert or mogrify, but I need to normalize (I guess) the level from picture 50 to 120 for example. It this feasible ?

note that I would like to process them with convert version
graphickmagick 1.3.21 2015-02-08 Q16

This is an Imagemagick forum. Graphicsmagick is not the same as Imagemagick. The Imagemagick developers do not maintain GraphicsMagick.

They started out the same, but split off a long time ago and Graphicsmagick has not kept up with the improvements in Imagemagick. So it is likely they do not have -auto-level.

Sorry I'm not too familiar with Imagemagick, How do I check the version from bash in UbuntuStudio 15.04, since I have both installed ?

If if it does not say Imagemagick, then try

Thanks, I updated my version and now I'm at the proper level.

Version: ImageMagick 6.8.9-9 Q16 i686 2015-01-06 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2014 ImageMagick Studio LLC
Features: DPC Modules OpenMP
Delegates: bzlib djvu fftw fontconfig freetype jbig jng jpeg lcms lqr ltdl lzma openexr pangocairo png tiff wmf x xml zlib


It seems to work well on multiple pictures.
But is there a way to average the level for multiple consecutive picture which are not all at the same exposure ?

Thanks for your help.

Use the mean and standard deviation from the image statistics to match all the images to one common image statistics. See snibgo's page at http://im.snibgo.com/gainbias.htm for the math and examples. You could also get the average of the mean and std from all the images and match each image to that set of statistics

I also have a histmatch script for unix at my link below. It attempts to match the histograms. But I suspect the mean and std technique might be the quickest and safest.

There are many possible ways of improving the images, depending on what you want or like. For example, converting to HCL and applying a gamma to lightness works well. While in HCL space, increasing Chroma a little also looks good:
You can use "-gamma X" to change all images to have the same mean, where X is a number:

X = log(old_mean)/log(new_mean)

snibgo wrote:
You can use "-gamma X" to change all images to have the same mean, where X is a number:

X = log(old_mean)/log(new_mean)

-auto-gamma does just that for a desired mean of 50%

I wish there was a -define to set the desired mean. But Anthony did not want to add that originally.

My script autogamma allows an arbitrary desired mean.

I tried both options above and they degrade the original picture. Part of it is better and part of it is degraded.
I tried a few options (auto-level, equalize, auto-gamma, normalize) but none of them is perfect because I work under different light scenarios.
Here is the original captured time-lapse video after ffmpeg put it together, I recorded for 3 days, 24hours, every 3 mins:
https://drive.google.com/file/d/0B0u3vN ... sp=sharing
the normalize gave the best result.
Thanks for your help.
Lionel