Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Fixes #6540 in a different way than #6551. It turns out the vector backends were already correct and the only bug was in the agg backend. So this just updates the agg backend to ignore the alpha on images.
This is because for the case of interpolation=='none' in a vector backend we explicitly do not want to touch the image data at all, so the alpha must be applied in the vector renderer instructions, not in the image data itself.
The Agg backend doesn't really make sense for that and we always transform the image, so it is a special case.
Cc: @tacaswell