Matrix transformation script on multi page document

[duangdoock]

Hi everyone
I've got a multi page document. Is it possible to run a script that could run a Matrix transformation (Object -> Transform) for the objects of pages 1,3,5,7 only?
Thanks

[spakin]

Yes! For each object, you'll need to determine if it intersects any of the pages you care about and, if so, apply your desired transformation. Here's the basic code structure I have in mind:

page_list = all_pages()
page_bboxes = [page_list[p - 1].bounding_box() for p in [1, 3, 5, 7]]
for obj in all_shapes():
    obb = obj.bounding_box()
    for pbb in page_bboxes:
        ibb = obb & pbb
        if ibb.x != inkex.transforms.BoundingInterval():
            # Apply transformation.

In the above, obb is the object's bounding box, pbb is the page's bounding box, and ibb is the intersection of the two bounding boxes. If the intersection is empty, ibb.x will equal the default inkex.transforms.BoundingInterval().

Object transformations are discussed in Applying individual transformations in the Simple Inkscape Scripting wiki. If you want to specify a transformation matrix explicitly, you can set obj.transform to an appropriate inkex.transforms.Transform as per Replacing the entire transformation.

[duangdoock]

Thanks for your reply. I'll make some tests. Is it possible to do a matrix transformation for a page, affecting all the objects in it?

[spakin]

I don't believe so. However, you can add all of the objects in the page to a group, transform the group, then ungroup it. (ungroup's default behavior is to preserve transformations.) See if this works:

page_list = all_pages()
page_bboxes = [page_list[p - 1].bounding_box() for p in [1, 3, 5, 7]]
for pbb in page_bboxes:
    # Acquire a list of all objects that intersect the current page.
    page_objs = []
    for obj in all_shapes():
        obb = obj.bounding_box()
        ibb = obb & pbb   # Intersection of the two bounding boxes
        if ibb.x != inkex.transforms.BoundingInterval():
            page_objs.append(obj)

    # Transform the page's objects.
    page_group = group(page_objs)
    page_group.rotate(-30)   # ...or whatever transform you want
    page_group.ungroup()

Note that I interchanged the loops from my previous answer to loop first over pages then over objects.

[duangdoock]

Thanks for this explanation. It's much appreciated.
Regards

[spakin]

FYI, inspired by this discussion, I introduced in f6ef0c6 an all_shapes method on page objects that returns all of the shapes on a page. Using all_shapes, the code I proposed earlier reduces to simply

for pageno, page in enumerate(all_pages()):
    if pageno + 1 not in [1, 3, 5, 7]:
        continue
    page_group = group(page.all_shapes())
    page_group.rotate(-10)   # ...or whatever transform you want
    page_group.ungroup()

[duangdoock]

Thanks very much! It simplifies the process. All the best