Openlayers / Deepzoom format

[Jan Harkes]

On Wed, Oct 03, 2012 at 03:50:12PM -0400, Jan Harkes wrote:
> On Wed, Oct 03, 2012 at 07:22:46AM +0200, PD Dr. M. Weihrauch wrote:
> > only supports tiles of 256x256 and deepzoom may have different
> > tile-sizes on the right border and the bottom border of the images.
> 
> I just looked at the openslide-python:openslide/deepzoom.py code and it
> looks like it will always return square (256x256) tiles.

And after looking a second time, it actually does clip the tiles at the
edge. It does already handle compositing the image data returned by
openslide onto a tile that is filled with the background color, so
changing the code to return fixed size tiles is (probably) fairly easy.

Openseadragon probably wouldn't like it though so I don't see a trivial
fix that would work well for all cases here.

So the dynamic tile server would have to use something like the following
(completely untested) code to support map viewers,

Jan


    from PIL import Image

    @app.route('/<slug>_osm/<int:level>/<int:col>_<int:row>.<format>')
    def osm_tile(slug, level, col, row, format):
        ### mapviewers expect to see 256x256 tiles at level 0
        level = level + 8

        format = format.lower()
        if format != 'jpeg' and format != 'png':
            # Not supported by Deep Zoom
            abort(404)
        try:
            tile = app.slides[slug].get_tile(level, (col, row))
        except KeyError:
            # Unknown slug
            abort(404)
        except ValueError:
            # Invalid level or coordinates
            abort(404)

        ### if the tile is clipped, paste it into a 256x256 tile.
        if tile.size != (256,256):
            full = Image.new('RGB', (256,256), '#000')
            full.paste(tile, (0,0))
            tile = full

        buf = StringIO()
        tile.save(buf, format, quality=app.config['DEEPZOOM_TILE_QUALITY'])
        resp = make_response(buf.getvalue())
        resp.mimetype = 'image/%s' % format
        return resp