pdftops – avoid excessive or unnecessary rasterization
Submitted by James Cloos @cloos
Assigned to poppler-bugs
Description
Currently PSoutputDev:: forces rasterization whenever the pdf (page?) has any tranparency or uses pattern image masks.
Instead it, as cairo does, should limit rasterization to the size of the non-opaque regions.
In particular, if the only non-opaque objects are images, then those images should be pre-composed and treated as opaque images.
Non-opaque images directly on the background should be composed to white.
Non-opaque images atop a constant opaque vector or image object should be composed to said underlying object’s constant colour and then opaquely painted atop the object.
For everything else, the area with non-opaque objects can be rasterized as the whole page currently is.
Looking at PSOutputDev::, this will take some work.