Fast gif resize

[pkieltyka]

imgry/imagick/imagick.go

Lines 195 to 199 in f7a2a8c

	// TODO: instead of Coalesce, better to change the offsets.
	// This is required for animated image resizing
	if !sz.Flatten && i.mw.GetNumberImages() > 1 {
	i.mw = i.mw.CoalesceImages()
	}

[pkieltyka]

The current imagick implementation for gif resizing will flatten each layer, which creates a larger in filesize image, and is MUCH slower to resize because it effectively resizes more bytes per frame to generate the image.

For example: http://imgry.pressly.com/test/fetch?url=http%3A%2F%2Fwww.thisiscolossal.com%2Fwp-content%2Fuploads%2F2015%2F04%2Fcine-1.gif&size=800x

this will load quickly because its already sized/cached -- but, try to change the size query param to 840x or 730x .. pick something ... it will take over 2 seconds. And compare the filesize to the original image url: http://www.thisiscolossal.com/wp-content/uploads/2015/04/cine-1.gif

if you open the gif in an image editor, you will see the layers (frames), the subsequent frames are actually offset positions, layered on top of eachother. Other gifs do use full frames and a 0,0 offset.

The goal is to not have to flatten each frame, and try to keep the frames intact, and resize the respective layers etc. to get the final image.

[xiam]

Closed by #9?