Variable opacities not supported for screenshot and movie requests

[Keith Hughitt]

For example:

Attempting to make a screenshot with a 50% opacity LASCO C3 layer on top of at 100% opacity LASCO C2 layer will result in a screenshot where both layers have a 100% opacity.

The problem relates to how ImageMagick handles conversion from an image type that supports alpha channels (PNG) to one that doesn't (JPG). When this occurs, ImageMagick discards the alpha channel resulting in an image that is completely opaque (http://www.imagemagick.org/Usage/formats/#summary).

[Keith Hughitt (keith-hughitt)]

Note: This currently only affects single layer requests on the main site.

[Keith Hughitt (keith-hughitt)]

The problem no only affects composite images for which non-overlapping layers have semi-transparent opacities. For example, attempting to create an AIA 304 screenshots at 50% opacity. The desired result would be a 50% transparent AIA layer on a black background. The actual result is currently a 100% opaque AIA image on a black background. On the other hand, creating composite images with overlapping EIT/AIA channels will work fine. Since the later is the more useful type of request and it is very unlikely for someone to need an image like a 50% transparent AIA one, I'm going to mark this bug as low priority.

For more information on the limitation see the discussion at: http://www.imagemagick.org/discourse-server/viewtopic.php?f=18&t=17540