On Fri, 29 May 2009, Stijn Sanders wrote:
> I'm converting an application from IM to GM, and I was using -draw
> "image dst-over ... to draw something 'under' another png with
> sertain sections transparant, but GM throws this error:
> Non-conforming drawing primitive definition (image)
I think that the underlying algorithm is similar to GM's 'Over'
composite operation. However, ImageMagick is swapping the pixel
roles for DstOver as if the two images were interchanged.
> I checked the available compose operators:
> but I don't think GM has the operator I need, (even worse: whichever
> operator I test it doesn't seem to do anything different... Xor and
> subtract should at least have something visible where the
> first-loaded png is not translucent?)
I think that 'gm composite' will offer more control. The -draw
operator is an additive environment which always has a backing canvas
and composition is on top of whatever is already drawn on that canvas.
When transitioning from ImageMagick to GraphicsMagick, it does not
help with understanding that ImageMagick renamed all of its composite
operators since the fork.
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/