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"""

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    Raw tile handling.

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"""

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from werkzeug import Request, Response, exceptions

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import pypngtile

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## Coordinates

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# width of a tile

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TILE_WIDTH = 256

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TILE_HEIGHT = 256

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# max. output resolution to allow

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MAX_PIXELS = 1920 * 1200

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def scale (val, zoom):

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    """

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        Scale dimension by zoom factor

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        zl > 0 -> bigger

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        zl < 0 -> smaller

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    """

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    if zoom > 0:

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        return val << zoom

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    elif zoom < 0:

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        return val >> -zoom

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    else:

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        return val

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def scale_center (val, dim, zoom):

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    """

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        Scale value about center by zoom.

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    """

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    return scale(val - dim / 2, zoom)

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    def render_region (self, request, image):

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        """

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            Handle request for an image region

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        """

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        width = int(request.args['w'])

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        height = int(request.args['h'])

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        x = int(request.args['x'])

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        y = int(request.args['y'])

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        zoom = int(request.args.get('zoom', "0"))

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        # safely limit

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        if width * height > MAX_PIXELS:

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            raise exceptions.BadRequest("Image size: %d * %d > %d" % (width, height, MAX_PIXELS))

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        x = scale(x, zoom)

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        y = scale(y, zoom)

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        try:

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            return image.tile_mem(width, height, x, y, zoom)

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        except pypngtile.Error as error:

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            raise exceptions.BadRequest(str(error))

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    def render_tile (self, request, image):

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        """

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            Handle request for image tile

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        """

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        width = TILE_WIDTH

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        height = TILE_HEIGHT

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        row = int(request.args['row'])

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        col = int(request.args['col'])

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        zoom = int(request.args.get('zoom', "0"))

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        x = scale(row * width, zoom)

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        y = scale(col * height, zoom)

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        try:

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            return image.tile_mem(width, height, x, y, zoom)

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        except pypngtile.Error as error:

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            raise exceptions.BadRequest(str(error))

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    def handle (self, request):

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        """

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            Handle request for an image

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        """

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        try:

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        except pypngtile.Error as error:

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            raise exceptions.BadRequest(str(error))

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        if 'w' in request.args and 'h' in request.args and 'x' in request.args and 'y' in request.args:

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            png = self.render_region(request, image)

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        elif 'row' in request.args and 'col' in request.args:

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            png = self.render_tile(request, image)

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        else:

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            raise exceptions.BadRequest("Unknown args")

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        return Response(png, content_type='image/png')