Need some help about transformation

[Yue Liu]

looks like I've figured it out.

On Tue, Jul 19, 2011 at 3:38 PM, Yue Liu <yue.liu at mail.com> wrote:
> Hello,
>
> In recent days I'm trying to fix the shape group shadow issues but I
> think I have some misunderstandings and made things even worse. Hope I
> can get some help.
>
> My design:
>
> get the shadow rectangle by shadowRect = shape->boundingRect();
> this will include the insets of shadow offsets and shadow blur caused
> shadow expansion.
>
> I think after that I'll get a rectangle with shape's origin inside it.
>
> create a buffer image with shadow rectangle's size in view zoomlevel.
> QRectF zoomedClipRegion = converter.documentToView(shadowRect);
> QImage sourceGraphic(zoomedClipRegion.size().toSize(),
> QImage::Format_ARGB32_Premultiplied);
>
> apply a transform to th qpainter which paints the shadow onto the image.
> this part confuse me very much, currently i did:
>
> //offset transformation on the buffer image in pixel, shape's own coordinate
> QTransform tm;
> tm.translate(d->offset.x(), d->offset.y());
> QTransform tr = shape->absoluteTransformation(&converter);
> QTransform offsetMatrix = tr * tm * tr.inverted();
>
> //set the absolute transformation to shape so it can draw in it's own
> coordinate system in pixel
> KoShape::applyConversion(painter, converter);
> // apply the offset transformation so it draws on the correct position
> on buffer image
> painter.setTransform(offsetMatrix * painter.transform());
>
> //process the image and paste the image to the canvas
> QPointF clippingOffset = zoomedClipRegion.topLeft();
> painter.drawImage(clippingOffset, sourceGraphic);
>
> But the result goes very starnge, the shadow rectangle changes a lot
> when shape is moving, and the shadow position is incorrect. I must
> have get something wrong. Anyone knows what's wrong with the
> implementation?
>
> in the attachment shape group part are commented since I haven't
> figure out the single shape part.
>
> Best Regards,
> Yue Liu
>