scaling down an image gives red and blue shadows?

[espressocannon]

I am trying to scale down some of my images, but they end up with an ugly red and blue shadow after re-sampling (changing the ratio of pixel number)

https://imgur.com/a/k1SU4

example above

(edited for clarity)

[fmw42]

Please always post your IM version and platform when asking questions. Also your exact command line and both the input and output images. There is no example where you have "example here"


See the top-most post in this forum "IMPORTANT: Please Read This FIRST Before Posting" at viewtopic.php?f=1&t=9620

For novices, see

viewtopic.php?f=1&t=9620
http://www.imagemagick.org/script/comma ... essing.php
http://www.imagemagick.org/Usage/reference.html
http://www.imagemagick.org/Usage/

[espressocannon]

Hi, thanks for the reply.

The version I am using is whatever is latest from apt-get on ubuntu server. I ran a apt-get update right before downloading, and this was yesterday, so unless something has changed since yesterday, I have the latest version from APT

What I am doing is two seperate things.

1. I am converting from RAW to JPG and resizing (not the example image above) using the following command:

convert nef:/media/kandeNAS/2013/Katarina 60s Glam/_DSC9864.NEF -resize 75% /media/kandeNAS/2013/Katarina 60s Glam/optim/_DSC9864.jpg

the "nef" and path are generated by the script based on file type, etc etc.

2. Resizing JPGS (as in the above linked image - here for your convenience: https://imgur.com/a/k1SU4 ) using the following command.

convert /media/kandeNAS/2012/2012-March/IMG_5558.JPG -resize 75% /media/kandeNAS/2012/2012-March/optim/IMG_5558.jpg

This produces the above example. where the shadows have a blue and red haze in them, in underexposed images, the effect is more pronounced.

[fmw42]

Sorry, but I need to know the exact version of ImageMagick and the date associated with it. Use

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convert -version

I also need to be able to download your input and output image. I do not know how to get those from imgur. I only see one image. Also it appears that I have to login and I have no access.

[fmw42]

Which of the two commands are giving you trouble? Or are you running both commands on the same image taking the output from the first command and using it for the input of the second command.

[espressocannon]

sorry about the confusion. If the image is JPG I run the JPG command on them - and if the image is RAW I run the RAW command on them. never both commands.

=======================================================================

here is the exact command I ran on this RAW image:

convert cr2:/media/kandeNAS/2012/2012-12-24/_MG_9449.CR2 -resize 75% /media/kandeNAS/2012/2012-12-24/optim/_MG_9449.jpg

Raw image and JPG output can be downloaded from this public dropbox folder (just hit download, you do not need to log in)

https://www.dropbox.com/sh/u9lljwajto70 ... EB5la?dl=0

=======================================================================

output of "convert -version"

Version: ImageMagick 6.8.9-9 Q16 x86_64 2017-07-31 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2014 ImageMagick Studio LLC
Features: DPC Modules OpenMP
Delegates: bzlib cairo djvu fftw fontconfig freetype jbig jng jpeg lcms lqr ltdl lzma openexr pangocairo png rsvg tiff wmf x xml zlib

PS. CORRECTION: This does not seem to occur on JPG > JPG - Only RAW (cr2) > JPG

[fmw42]

I downloaded the example.nef from https://www.online-convert.com/file-format/nef and processing it on IM 6.9.9.23 Q16 Mac OSX with the following command:

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convert nef:example.nef -resize 75% example.jpg

The result was a bit darker than the new file, but the colors were good.

So I reprocessed as

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convert nef:example.nef -resize 75% -auto-level -gamma 1.5 example4.jpg

and get a better match of brightness and contrast.

I see no signs of color shifts

[fmw42]

I ran your cr2 image with your command on my IM 6.9.9.23 Q16 Mac OSX and got no red speckle distortion and you show in your output.

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convert cr2:"_MG_9449.CR2" -resize 75% test1.jpg

Also what version of dcraw and libjpeg?

I am using

dcraw @9.27.0_2
jpeg @9b_0

Perhaps you need to upgrade one or both.

[fmw42]

6.8.9.9 is over 100 versions old. You might consider upgrading IM also. However, it looks to be patched at July 2017. So it may be OK. Though you could check to see if there is a more current patch. My guess is it is your version of dcraw.

[espressocannon]

I ran your cr2 image with your command on my IM 6.9.9.23 Q16 Mac OSX and got no red speckle distortion and you show in your output.

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convert cr2:"_MG_9449.CR2" -resize 75% test1.jpg

Also what version of dcraw and libjpeg?

I am using

dcraw @9.27.0_2
jpeg @9b_0

Perhaps you need to upgrade one or both.

hello. I posted my results of convert -version above. Here it is again:

Version: ImageMagick 6.8.9-9 Q16 x86_64 2017-07-31 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2014 ImageMagick Studio LLC
Features: DPC Modules OpenMP
Delegates: bzlib cairo djvu fftw fontconfig freetype jbig jng jpeg lcms lqr ltdl lzma openexr pangocairo png rsvg tiff wmf x xml zlib

I do not know how to get the versions of dcraw or libjpeg

dcraw -version gives me "The program 'dcraw' is currently not installed."
libjpeg -version gives me "command not found"

[espressocannon]

6.8.9.9 is over 100 versions old. You might consider upgrading IM also. However, it looks to be patched at July 2017. So it may be OK. Though you could check to see if there is a more current patch. My guess is it is your version of dcraw.

shouldn't the version from APT be the most current version?

Why would there be a version that is 100 versions old on APT?

[fmw42]

Linux systems patch old version. Your version by number is old, but has been patched most recently in July 2017. So is likely current. But since I do not know what the latest patch is, I cannot say. Furthermore I dislike the process of patching, since patches can be bad or missed. Thus it is hard to really tell what version is being used. If you believe the patch date then it goes back to IM between 6.9.9.0 and 6.9.9.5, but current IM is as 6.9.9.23.

try

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convet -list format

JPEG* JPEG rw- Joint Photographic Experts Group JFIF format (90)
JPG* JPEG rw- Joint Photographic Experts Group JFIF format (90)

Also

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dcraw

Raw photo decoder "dcraw" v9.27

[espressocannon]

Linux systems patch old version. Your version by number is old, but has been patched most recently in July 2017. So is likely current. But since I do not know what the latest patch is, I cannot say. Furthermore I dislike the process of patching, since patches can be bad or missed. Thus it is hard to really tell what version is being used. If you believe the patch date then it goes back to IM between 6.9.9.0 and 6.9.9.5, but current IM is as 6.9.9.23.

try

Code: Select all

convet -list format

JPEG* JPEG rw- Joint Photographic Experts Group JFIF format (90)
JPG* JPEG rw- Joint Photographic Experts Group JFIF format (90)

Also

Code: Select all

dcraw

Raw photo decoder "dcraw" v9.27

my JPG results from convert -list format does not look the same: I get

JPEG* JPEG rw- Joint Photographic Experts Group JFIF format (80)
JPEG* JPEG rw- Joint Photographic Experts Group JFIF format (80)

Here are some more attempts to make things work:::

"dcraw -T nephew.CR2" provides the correct result. (outputs a TIFF file - not ideal)

trying to convert TIFF to JPG with imagemagick using: "convert nephew.tiff nephew-fromtiff.jpg" produces the correct result but throws a LOT of errors (not comfortable with errors when archiving thousands of files)

on UBUNTU - "convert cr2:nephew.CR2 nephew-ubuntu.jpg" provides the version with the glitched-out shadows (as above).

on WINDOWS - "magick nephew.CR2 nephew-windows.jpg" - Produces correct result (not ideal as I don't want my work system to be doing this - it's going to take about two months of full CPU to get thru my library)

Here is a dropbox folder with all above results and the source. as well as a text file with all the errors produced from "convert nephew.tiff to nephew-fromtiff.jpg"
https://www.dropbox.com/sh/4pk7ouwghkzf ... SqFza?dl=0

[fmw42]

All your messages are warnings. You can suppress them by adding -quiet to your command line after convert.

You might try upgrading JPEG. That version is old.

Using CR2 directly should produce a JPG if you use the proper arguments.

Did you check the dcraw version as I showed above?

[fmw42]

P.S. When using draw directly it probably know more about brightness corrections from its meta data that IM does not know. So that is likely why my IM conversion is darker than the cr2 original. Nevertheless you should not be getting any red speckles.

I am not an expert on raw formats such as NEF or CR2. So perhaps one of the photographer experts who use those formats can comment further on the differences in brightness between IM conversion and direct conversion.