Legacy ImageMagick Discussions Archive

I have a script that generates and image and such and I want to overlay this on Google Maps.

The only problem I have now is that I want to make the image (PNG) something like 65% transparent. Can this be done? I'm not sure if I am doing something wrong, as every argument I've tried either gives me no result or something I do not want.

try

convert image.png -alpha set -channel a -evaluate set 65% +channel newimage.png

see http://www.imagemagick.org/Usage/transf ... aluate_set

what IM version, platform and OS?

can you post a link to your image(s)?

Thank you very much for the response.

This is the image I want to make transparent.
http://inxwireless.com/work/outage-orig.png

the -alpha argument doesn't take:
-> convert outage-orig.png -alpha set -channel a -evaluate set 65% +channel outage.png
convert: unrecognized option `-alpha'.

convert outage-orig.png -channel a -evaluate set 65% +channel outage.png
http://inxwireless.com/work/output.png

ImageMagick.i386 6.2.8.0-4.el5_5.3
-> cat /etc/redhat-release
CentOS release 5 (Final)
32-bit

Your input image does not look like the correct link. The page is missing all images.

Your version of IM is too old (over 400 versions old) to use -alpha set and perhaps -evaluate set

If you cannot upgrade IM (highly recommended!), then

try

convert image.png -matte -channel a -evaluate set 65% +channel newimage.png

or

convert image.png -matte -channel a -evaluate set 35% +channel newimage.png

as the alpha channel at that time might be really opacity and not transparency

if that fails, try

convert image.png \( -clone 0 -fill "gray(65%)" -colorize 100% \) -compose copy_opacity -composite result.png

or

convert image.png \( -clone 0 -fill "gray(35%)" -colorize 100% \) -compose copy_opacity -composite result.png

I fixed both links to images above, they should work now. Sorry about that.

I tried the first two commands and I don't see any differences between the output images and original.

The third command is missing a quote somewhere, so I did:
-> convert outage-orig.png \( -clone 0 -fill grey -colorize 100% \) -compose copy_opacity -composite result.png
Of which I don't see any change in the image either.

http://inxwireless.com/work/newimage.png
http://inxwireless.com/work/result.png

I'm guessing it has something to do with how the image is colored (alpha, palette, something of that sort). Total guess, mind you!

try this (I fixed the quote and added +matte to turn off any existing alpha channel, sorry about the quote)


convert newimage.png \( -clone 0 -fill "gray(35%)" -colorize 100% \) +matte -compose copy_opacity -composite newimage_result.png

or


convert newimage.png \( -clone 0 -fill "gray(65%)" -colorize 100% \) +matte -compose copy_opacity -composite newimage_result.png


Then drop it on your browser's white background and you should see it look somewhat whiter as it is overlaid on the white background.

This also works for me:

convert newimage.png -matte -channel a -evaluate set 35% +channel newimage_result2.png

I upgraded versions as your initial suggestion put. Since there is no repo for it, I had to do it semi-manually. This guide was used and was flawless short of the version (I used 6.6.9)
http://en.citizendium.org/wiki/User:Dan ... k_6.6.2-10

-> convert --version
Version: ImageMagick 6.6.9-8 2011-05-10 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2011 ImageMagick Studio LLC
Features: OpenMP

This worked! Thanks so so much!
convert outage-orig.png \( -clone 0 -fill "gray(35%)" -colorize 100% \) +matte -compose copy_opacity -composite newimage_result.png

With your new release, the other method should work also and is shorter and faster.

convert newimage.png -alpha set -channel a -evaluate set 35% +channel newimage_result2.png

or


convert newimage.png -alpha opaque -channel a -evaluate set 35% +channel newimage_result2.png

fmw42 wrote:try

convert image.png -alpha set -channel a -evaluate set 65% +channel newimage.png

see http://www.imagemagick.org/Usage/transf ... aluate_set

what IM version, platform and OS?

can you post a link to your image(s)?

It works, but there is one problem.
It replaces the "already present transperency" my pictures have with "black".

Any way to keep that transparancy aswell ?

So what do you want to happen? You want to reduce the opacity of all pixels from whatever they have by 65%. If so, try this

Perfect