Legacy ImageMagick Discussions Archive

This works convert 0.tif 1.tif 2.tif min.tif max.tif -poly "1,1,1,1,1,1,-1,1,-1,1" nr.tif This is not working, though it probably should convert 0.tif 1.tif 2.tif min.tif max.tif -function Polynomial "1,1,1,1,1,1,1,-1,1,-1" nr.tif My next question is how should I write this for 3...

Thanks. The syntax makes sense now... Output with your command produces high pixel values Colorspace: sRGB Depth: 16-bit Channel depth: red: 16-bit green: 16-bit blue: 16-bit alpha: 1-bit Channel statistics: Pixels: 11793570 Red: min: 48158 (0.734844) max: 65535 (1) mean: 58314.6 (0.889824) standard...

Version: ImageMagick 6.8.9-9 Q16 x86_64 2017-05-26 http://www.imagemagick.org xubuntu 16.04 If I reword my question. I have 3 sRGB images and the min and max of the image set to combine using -poly. The idea is to reject outliers and reduce noise in the image stack. I am unsure of the correct syntax...

I'm interested in what is happening in the polynomial below. I am not sure that the expression is correct, given the following image set 0.tif 1.tif 2.tif max.tif min.tif - where convert 0.tif 1.tif 2.tif -evaluate-sequence Min min.tiff convert 0.tif 1.tif 2.tif -evaluate-sequence Max max.tiff With ...

Thanks Fred. That's what I thought. Saved me a lot of playing around.

-auto-level might be necessary then.

A short query.

Having applied -evaluate min=% and -evaluate max=%

where % = a chosen value

Is quantum range restored to the image automatically with the new values applied or is it necessary to normalize or auto-level the image.

I may be missing a salient point about IM operation.

I think gray level is correct.

Winsorizing would be very handy.

I'm looking for a way of implementing a Winsorized Sigma Clipping routine in IM and perhaps the thread has steered away from that to finding hot and cold pixels by other means. So, getting back on track and referring to the link is there a way to do this in IM or perhaps something similar. In a nuts...

Thanks fwm42. I will have a look again. I have tried many of your scripts. That makes sense. But looking at the magnitude of the slopes in your supplied image, I can't see any changes in brightness. This is a crop from the combined sRGB image. The isolated bright red green and blue pixels are artefa...

I have not gone to any length to correct the terminology used so far. So this is probably a good time to reiterate my second post. Hot pixels cosmic ray hits and other unwanted signal is characterized by a sudden change in contrast and/or brightness, whereas the transition around stars is gradual. I...

try converting anything less than 50% brightness to full black. Adjust the 50% as desired convert RCrop.tiff -black-threshold 50% RCrop_bt50.tiff Does that do what you want? To retain image features I need to do something like this, it's partly effective, but all over the image rather than to an is...

The scripts produce different effects and several produce very good noise reduction. I think the solution I am looking for is a pixel comparison and add or subtract from the pixel as required - defined by surrounding pixels of 'normal' exposure values. Normal meaning they could be any value but repr...

I have tried the methods suggested and this has helped clarify what I am trying to achieve. Hot pixels cosmic ray hits and other unwanted signal is characterized by a sudden change in contrast and/or brightness, whereas the transition around stars is gradual. I need to find the offending pixels and ...

Does the average exclueing min/max routine clip min/max values or reassign new mean values to those pixels.

Similarly, would a winsorizing routine be possible with IM. Winsorizing is perhaps a better choice for dealing with outliers in astronomical images.