Compose modulate creates very dark results

[tbraber]

In the latest versions (6.7.8.x) I am not able to use the -compose modulate -composite command as in previous versions.

If I use the command:

convert image.jpg watermark.gif -compose modulate -composite test.jpg

The result is a very dark image.
I have tried with -colorspace sRGB and -colorspace RGB in every possible way but could not produce a watermarking like result that worked fine in older versions.

I found out that it worked in versions up to 6.7.6.9 but not in 6.7.8.x . ( could be that 6.7.7.x worked but I did not test that yet)

In the example, the watermark.gif is a grayscale image created with emboss filter with 50% gray level
The image.jpg is a normal sRGB image.

[snibgo]

The documentation (http://www.imagemagick.org/Usage/compose/), discusses only the case where the overlay is black and white, not gray. Perhaps you now need to use the brightness seting. Can you provide samples?

Note that 6.7.8 isn't the latest version.

[tbraber]

Note that 6.7.8 isn't the latest version.

Sorry I meant version 6.8.0-7

Here is an example of a watermark image http://webhop.mediafiler.net/sol/files/ ... ymbol2.gif
Here is an example of the source image http://webhop.mediafiler.net/sol/files/ ... /image.jpg

The modulate option was/is a perfect way to create a watermark as described in the documentation: http://www.imagemagick.org/Usage/compose/#watermark

[snibgo]

It looks to me that ...

Code: Select all

convert image.jpg watermark_symbol2.gif -set colorspace RGB -compose modulate -composite test.jpg

... gives the result that old IM versions did.

This is another consequence of IM generally converting from sRGB to RGB space before doing the required operation. Telling IM that the image is already RGB prevents the conversion.

[anthony]

The question is why is it doing that.

The answer is more than likely the nature of how compose modulate works, as it is one of the few compose methods that is colorspace dependant.

[tbraber]

This helped partial, but now the image has dark edges around the watermark and dark spots if the image contains white parts.
See example: http://webhop.mediafiler.net/sol/files/ ... ertest.jpg or http://webhop.mediafiler.net/sol/files/ ... _6aa55.jpg

[snibgo]

"-compose modulate composite" seems to work okay in v6.8.5 but not 6.8.6.

[tbraber]

I am testing in version 6.8.5 at the moment and there the dark edges and clipping pixels appear. This was working correct in version 6.7.6.9

[snibgo]

Sorry, I should have supplied exact version numbers:

6.8.5-0 "-compose modulate composite" seems to work

6.8.5-8 "-compose modulate composite" creates black pixels where either image was white

6.8.6-0 as for 6.8.5-8

All on Windows 7.

I don't know exactly what modulate is supposed to do, but the black pixels are really ugly and obviously (I think) a bug.

[magick]

We can reproduce the problem you posted and have a patch in ImageMagick 6.8.6-2 Beta available by sometime tomorrow. Thanks.

[tbraber]

I have tested with version 6.8.6-2 Q16 this version still has the same problem.

[magick]

We get http://www.imagemagick.org/watermark.jpg. Identify the problem with this result.

[tbraber]

In your image there are also some black dots in places where they should be white. Best is to test with a light image that contains some full white (255,255,255) dots.
They will become black then.
This is the same image but with IM version 6.7.7 http://webhop.mediafiler.net/sol/files/ ... _405ac.jpg

[magick]

We can reproduce the problem you posted and have a patch in ImageMagick 6.8.6-3 Beta available by sometime tomorrow. Thanks.

[tbraber]

SOLVED: Tested with 6.8.6-3 and Modulate works again as good as it did in older versions.

Thanks.