combining 2 images NOK windows last version but OK linux

[willemijns2]

Hello,

took any image like https://imagemagick.org/image/wizard.png

I created an empty page to combine images on it and i began by the first :

Result:
- (abnormal) B&W image in latest windows public build
- (good) colorized image on Ubuntu 18.04 LTS and former windows build i lost the version number.

it is due to a recent change on IM ? on LIBPNG ?

Linux bash & Windows batch follows :

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# imagemagick 6.9.7-4 Q16 x86_64 20170114 
rm emptypage.png
rm workswell.png
wget https://imagemagick.org/image/wizard.png
convert -size 2480x3508 xc:white emptypage.png
convert emptypage.png -strip wizard.png -geometry 150%%x150%%+100+100 -composite workswell.png
xdg-open workswell.png
read $r
read $r
read $r


del emptypage.png
del bad.png
..\ImageMagick-7.0.8-64-portable-Q16-x64\convert -size 2480x3508 xc:white emptypage.png
..\ImageMagick-7.0.8-64-portable-Q16-x64\magick convert emptypage.png -strip wizard.png -geometry 150%%x150%%+100+100 -composite bad.png
start bad.png
pause

[fmw42]

I am not sure I understand your question. Are you saying you get an error from

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convert -size 2480x3508 xc:white emptypage.png

What do you get from

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convert -version

What is your version of libpng?

You can see that from

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convert -list format

and look at the end of the line for PNG

[willemijns2]

Hello, to simplify: the whole script works with a former linux version but not with the latest windows build....

One hour ago, i found an old windows IM version on my harddisk, i tested with this version and now i can confirm that my script:
- works with 7.0.8-28 => image is colorized (libpng 1.6.35)
- not works with 7.0.8-64 => image is B&W (libpng 1.6.37)

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set num=28
set num=64
del emptypage.png
del bad.png
..\ImageMagick-7.0.8-%num%-portable-Q16-x64\convert -size 2480x3508 xc:white emptypage.png
..\ImageMagick-7.0.8-%num%-portable-Q16-x64\magick convert emptypage.png -strip wizard.png -geometry 150%%x150%%+100+100 -composite bad.png
start bad.png
pause

[fmw42]

Add -colorspace sRGB right after reading in emptypage.png in your second command. The white image is being treated as single channel grayscale, but should be 3 channel truecolor, since named colors even if black or white are supposed to be treated as color not grayscale. I confirm your issue on IM 7.0.8.64 Q16 Mac OSX and I think it is a bug. But lets get a reading from the IM developers.

This works for me as a workaround. But one should not have to add -colorspace sRGB, in my opinion for the reason above.

Code: Select all

magick -size 2480x3508 xc:white emptypage.png
magick emptypage.png -colorspace sRGB -strip wizard.png -geometry 150%x150%+100+100 -compose over -composite good.png

Also for IM 7, use magick, not magick convert. Magick replaces Convert.

[willemijns2]

the same

[willemijns2]

you modified your message so i answer that your 2 suggestions does not works with latest build and works with the former 7-0-8-28 :-X

[fmw42]

Sorry, see my changed solution -- add -colorspace sRGB after reading emptypage.png

[willemijns2]

i saw a second modification of your reply, ok you confirm the bug... and your workaround of forcing sRGB works !

seems "-compose over" is not mandatory on my case

[fmw42]

-compose over is the default. But I always add it, especially when I have done other compose methods prior in the command line to reset it.

[willemijns2]

on a "dev way" it is a regression because it worked with 7-0-8-28

BUT

- Creating a white or black empty page can be build with only 2 colors = grayscale
- Creating a yellow, brown or other blue empty page needs morethan 2 colors so no problem !

I understand it can be a dilemna for B&W :-X maybe IM devs or libpng devs changed their mind ???