Method get

app/api/tasks.py:551–660

Generate a thumbnail on the fly for a particular task

(self, request, pk=None, project_pk=None)

class TaskThumbnail(TaskNestedView):
    def get(self, request, pk=None, project_pk=None):
        """
        Generate a thumbnail on the fly for a particular task
        """
        task = self.get_and_check_task(request, pk)
        orthophoto_path = task.get_check_file_asset_path("orthophoto.tif")
        if orthophoto_path is None:
            raise exceptions.NotFound()

        thumb_size = 256
        try:
            thumb_size = max(1, min(1024, int(request.query_params.get('size', 256))))
        except ValueError:
            pass

        with rasterio.open(orthophoto_path, "r") as raster:
            ci = raster.colorinterp
            indexes = (1, 2, 3,)

            # More than 4 bands?
            if len(ci) > 4:
                # Try to find RGBA band order
                if ColorInterp.red in ci and \
                        ColorInterp.green in ci and \
                        ColorInterp.blue in ci:
                    indexes = (ci.index(ColorInterp.red) + 1,
                                ci.index(ColorInterp.green) + 1,
                                ci.index(ColorInterp.blue) + 1,)
            elif len(ci) < 3:
                 raise exceptions.NotFound()
            
            if ColorInterp.alpha in ci:
                indexes += (ci.index(ColorInterp.alpha) + 1, )
            
            if task.crop is not None:
                cutline, (minx, miny, maxx, maxy) = geom_transform_wkt_bbox(task.crop, raster, 'raster')

                w = maxx - minx
                h = maxy - miny
                win = rasterio.windows.Window(minx, miny, w, h)
                ratio = w / h
                if ratio > 1:
                    out_width = thumb_size
                    out_height = int(thumb_size / ratio)
                else:
                    out_height = thumb_size
                    out_width = int(thumb_size * ratio)


                with WarpedVRT(raster, cutline=cutline, nodata=0) as vrt:
                    rgb = vrt.read(indexes=indexes, window=win, fill_value=0, out_shape=(
                        len(indexes),
                        out_height,
                        out_width,
                    ), resampling=rasterio.enums.Resampling.nearest)
                img = np.zeros((len(indexes), thumb_size, thumb_size), dtype=rgb.dtype)
                y_offset = (thumb_size - out_height) // 2
                x_offset = (thumb_size - out_width) // 2