Question: how is a region extracted?

[jcupitt at gmail.com]

Hi Martin,

On 30 August 2017 at 19:49, PD Dr. M. Weihrauch
<m.weihrauch at smartinmedia.com> wrote:
> If you extract a certain region from a zoom level via OpenSlide, how
> does OpenSlide do that?

It varies with the image format. For most of them, the file contains
raw images from the camera, plus some metadata saying how they should
be pasted together (position, rotation, scale, opacity). To render a
region of the output image, openslide decompresses all images which
touch that region, then blends them together to the output using
Cairo.

They also usually contain extra levels for zooming out, plus sets of
extra images for things like barcodes.

SZI should be a lot simpler since you have constant overlaps and positions.

John