- [BACK_INCOMPAT] `fabric.StaticCanvas#backgroundImage` and `fabric.StaticCanvas#overlayImage` are `fabric.Image` instances. `fabric.StaticCanvas#backgroundImageOpacity`, `fabric.StaticCanvas#backgroundImageStretch`, `fabric.StaticCanvas#overlayImageLeft` and `fabric.StaticCanvas#overlayImageTop` were removed.
- [BACK_INCOMPAT] `fabric.Text#backgroundColor` is now `fabric.Object#backgroundColor`
- [BACK_INCOMPAT] Remove `fabric.Object#toGrayscale` and `fabric.Object#overlayFill` since they're too specific
- [BACK_INCOMPAT] Remove `fabric.StaticCanvas.toGrayscale` since we already have that logic in `fabric.Image.filters.Grayscale`.
- [BACK_INCOMPAT] Split `centerTransform` into the properties `centeredScaling` and `centeredRotation`. Object rotation now happens around originX/originY point UNLESS `centeredRotation=true`. Object scaling now happens non-centered UNLESS `centeredScaling=true`.
- [BACK_INCOMPAT] Object rotation now happens around originX/originY point UNLESS `centerTransform=true`.
- [BACK_INCOMPAT] fabric.Text#textShadow has been removed - new fabric.Text.shadow property (type of fabric.Shadow).
- [BACK_INCOMPAT] fabric.BaseBrush shadow properties are combined into one property => fabric.BaseBrush.shadow (shadowColor, shadowBlur, shadowOffsetX, shadowOffsetY no longer exist).