Legacy ImageMagick Discussions Archive

Thank you fwm42 - I have found the problem - wrong use of the 'Grey option with -separate - silly mistake. can I improve on the following? convert images -separate %d.tiff process all three channels as in previous post then as suggested convert images -set colorspace sRGB -combine output_image.tiff ...

I am having trouble recovering color data from a set of RGB images, following some complex processing. It's experimental at this stage to compare the results of individual channel processing and processing without separating the RGB channels. I have four RGB images (16 bit .tiff) - b d f and l. Proc...

I think this is solved. The order of the operators is important. This is an effective method of creating a master flat that does not over correct or under correct the light frame pixel values during division.

From what I read, the idea of dividing the flats by mode is to correct the multiplicative errors in the flat frames, before combining them. My application, above, is not correct because I am dividing the master flat (all the combined flats) by the mode. I realise now that the individual flats should...

This writes the histogram to /tmp/mode.txt and cuts the mode value, as well as removing the leading whitespace to write mode as a variable $MODE convert *.tiff -evaluate-sequence median combined_flat.tiff >/dev/null 2>&1 convert combined_flat.tiff -format "%c" histogram:info: | sort -r...

That's no problem. Thanks again. Appreciate the assistance. Still working on the master_flat/mode method which is a bit of challenge. In the meantime I need a work around that produces clean light frames with reasonable pixel values. This works quite well - keep the processing linear. I found includ...

Apologies. The value of the light frame pixels is reduced when dividing the lights by the auto-leveled master flat. I am then normalizing the lights to increase the pixel values. I will try the other operators - so far median and auto-level produce flat frames that divide correctly and don't over or...

This is a work around, for the time being, which may satisfy the need. Pixel values and appearance indicates its not far off. This median combines the flats for noise reduction and auto-levels the master_flat, which produces a nice clean division of the light frames. Problem is it also creates very ...

Thanks again. I think this can be made to work. Something like this in my bash script mode=$(convert image -format "%c" histogram:info:  | sort -r -k1 | head -n 1) convert master_flat -format "%[fx:$mode]" info: | something here to pipe result I suspect this is not quite correct....

All the files are 16 bit integer CFA monochrome tiff files Source IRAF image processing "If during flat field exposure, the light source flickered or faded, the individual flats would have slightly different average values throughout the image. This would throw off the median combine in that it...

In astronomical image processing, a flat is an image taken at infinity illuminated by an even/flat light source to reveal dust, vignetting and other artifacts in the optical train. Probably, you know it by another name. To isolate the signal in an image from noise and other artifacts we can apply th...

I am working on a method of combining flat frames (3 at this stage) for flat division of a number of images. Following subtraction of the offset/bias from the flat frames, they are averaged into a single master flat; as follows convert -average -auto-level 3xflats.tiff master_flat.tiff this produces...

Thanks fwm42. I must admit to getting a little bit lost in the jargon. Using a real world example, I came up with the following using convert. I think this is correct; that is, the bias is subtracted from the frame (light, flat whichever) leaving the frame minus its bias. convert frame.tiff bias.tif...

Hi. I am attempting to show the difference between two files, image1 and image2, where image1 contains image2. Image1 is "the image" and image2 is fixed pattern noise. I want to remove the fixed pattern noise with a template, which is image2 I'm new to imagemagick and this has me stumped. ...