possible bug -compose blend IM 6.5.4-7 (HDRI)

[fmw42]

IM 6.5.4-7 Q16 HDRI

This works:

composite -blend 50 logo: \( -size 640x480 xc:black \) tmp1.png

Resulting image is half bright (mixed with black 50% each)


But neither of the following work. They just copy both input images to a two image output tmp2-0.png, tmp2-1.png

convert logo: \( -size 640x480 xc:black \) +swap \
-compose blend -set option:compose:args 50 tmp2.png

convert logo: \( -size 640x480 xc:black \) +swap \
-set option:compose:args 50 -compose blend tmp3.png


I have not checked to see if it works with non-hdri

[magick]

Try this:

• convert logo: \( -size 640x480 xc:black \) +swap -compose blend -set option:compose:args 50 -composite tmp2.png

[fmw42]

yes, I don't know how I missed that. But I seem to do it at times. thanks. sorry for the false alarm.

[anthony]

Don't worry too much about that mistake. I have made it many times myself.

[fmw42]

Thanks. I think I got overwhelmed by the -set option:compose:args and just forgot about -composite.

But it is strange to me that -compose seems to be the only setting that is used by one and only one option (-composite). Just wondering why -composite is needed at all in this case. If one specified -compose then it has to be followed by -composite. Thus why can it not be automatically assumed and filled in by IM.

I understand the philosopy that there are settings that don't do anything unless followed by an option. But -compose seems different from others such as -background, -fill etc that can be used by many options.

Anyway just a thought and comment as to why I get confused from time to time on this issue.

[anthony]

-compose is not used ONLY by -composite

It is also used by: -flatten, -mosaic, -layers merge, -layers composite
It is also indirectly used by; -border, -frame, -extent

A complete list of known operators that use it is on the IM Examples Compose Page...
http://www.imagemagick.org/Usage/compose/#compose

Other operators also use it internally but do not use the user defined compose setting, these include GIF animation operators such as -coalesce, -dispose, and -layer optimize_frames, as well as more complex operators like -polaroid and -draw. Also the commands "compare" and "montage" make use of image composition.