Copy-opacity to cut out transparent mask -composite problems

[weatherbadger]

Hi

I'm trying to cut out a transparent mask-hole in my wave charts so an underlying land-map will show through in a web-browser.

I'm starting with http://www.weatherbadger.com/Charts/test/wave2.png

and have a landmask http://www.weatherbadger.com/Charts/tes ... transp.png - if you open this with GIMP you can see the land is transparent.

These two images are the same height but the wave2.png is slightly wider - with a colorbar on the right hand side.

I've got as far as:

Code: Select all

convert wave2.png wave_transp.png -compose copy-opacity -composite wave-no_cbar.png

which works BUT it is making the right hand side of the wave2.png transparent which cuts off the color-bar: http://www.weatherbadger.com/Charts/tes ... o_cbar.png
It would appear that my -composite is making everything outside the mask image tranparent also.

I've tried -gravity west but think I'm probably not using -composite right. I can change the landmask to a black rather than transparent image if that helps

Thanks for any suggestions.

WB

[snibgo]

You can give a third image that will limit the dimensions of the composite. As you want this limit to be the source image you can simply clone it:

convert wave2.png wave_transp.png +clone -compose copy-opacity -composite wave-with_cbar.png

[weatherbadger]

+Clone - I've never have come up with that.

Just tried it and it works. Brilliant.

Many thanks
WB

[snibgo]

Good stuff. Send a bit of sunshine over towards Cambridge, would you?

"-gravity West" shouldn't make any difference. The default is NorthWest, but your source and destination images are the same height so NorthWest, West and SouthWest should give the same result.

[anthony]

Hi

I'm trying to cut out a transparent mask-hole in my wave charts so an underlying land-map will show through in a web-browser.

I'm starting with http://www.weatherbadger.com/Charts/test/wave2.png

and have a landmask http://www.weatherbadger.com/Charts/tes ... transp.png - if you open this with GIMP you can see the land is transparent.

As the images already has transparency, then you want to use a duff-porter composition.
http://www.imagemagick.org/Usage/compose/#duff-porter

The composition names make it very obvious as to pick what compose method you want to use.