v0.6.2

Fixed

• A mask, a clip or a filter region in object bounding box units applies to an <image>, and to a group that
  holds one. WeasyPrint has no bounding box for an image: the mask was left out and the image drawn opaque.
  The flat SVG writes the alpha of an image, since 0.6.1 each blur, as such a mask: weasysvg-convert, which
  pandoc draws the SVG of a DOCX with, drew the shadow of the OpenStreetMap logo as a dark rectangle.
• An element under a soft mask draws in a group, which the mask cuts once. PDFium and Poppler applied the mask
  again inside the cell of a pattern: a gradient fill under a mask of 0.5 showed at 0.25, an SVG pattern fill
  vanished. In PDF the soft mask of an image with alpha replaced the mask: a masked image drew unmasked. WeasyPrint
  alone has these gaps too.
• feColorMatrix and feComponentTransfer recolor the pixels of an image too, as they recolor the paint of a
  shape, within MAX_PIXEL_WORK. cairo turns a soft mask white through such a filter: the shading of the
  flat SVG of Tux was missing.

Full changelog: v0.6.1...v0.6.2