3 Commits

Author	SHA1	Message	Date
Lovell Fuller	f19b6c48ca	Skip normalise operation for images with one colour ... It didn't play nicely with premultiplication	2015-06-01 14:21:02 +01:00
Daniel Gasienica	ef8db1eebf	Premultiply alpha channel to avoid dark artifacts during tranformation ... Add `Sharp.compare(file1, file2, callback)` function for comparing images using mean squared error (MSE). This is useful for unit tests. See: - https://github.com/jcupitt/libvips/issues/291 - http://entropymine.com/imageworsener/resizealpha/	2015-06-01 14:21:02 +01:00
Daniel Gasienica	64f7f1d662	Add experimental overlayWith API ... Composites an overlay image with alpha channel into the input image (which must have alpha channel) using ‘over’ alpha compositing blend mode. This API requires both images to have the same dimensions. References: - http://en.wikipedia.org/wiki/Alpha_compositing#Alpha_blending - https://github.com/jcupitt/ruby-vips/issues/28#issuecomment-9014826 See #97.	2015-06-01 14:21:01 +01:00