turf.bboxClip returns a polygon instead of a MultiPolygon

[tsairinius]

I'm using turf.bboxClip to clip a portion of a polygon...

const originalPolygon = turf.polygon([
    [[10, 10], [15, 10], [20, 10], [20, 5], [15, 5], [15, 0], [20, 0], [20, -5], [15, -5], [10, -5], [10, 10]]
])

const bbox = [17, -10, 25, 20]
const clippedPolygon =  turf.bboxClip(originalPolygon, bbox)

Here's the result:

blue = bounding box
green = original polygon
red = the clipped polygon

Notice that the two red rectangles within the bounding box are connected by a line. I would have expected the clipped portion of the polygon to be represented by a MultiPolygon containing two polygons for each of the rectangles. Instead, the rectangles are grouped as a single polygon (hence the line connecting them). Is there any way to have them be represented as two separate polygons?

[smallsaucepan]

Hi @tsairinius. Can you please attached the returned geojson (the red rectangles)?

[tsairinius]

Sure, here's the geojson:

{"type":"Feature","properties":{},"geometry":{"type":"Polygon","coordinates":[[[17,10],[20,10],[20,5],[17,5],[17,0],[20,0],[20,-5],[17,-5],[17,10]]]}}

[stevage]

Confirming this. As a test case:

In:

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "coordinates": [
          [
            [
              60,
              47
            ],
            [
              65,
              49
            ],
            [
              70,
              46
            ],
            [
              65,
              51
            ],
            [
              60,
              47
            ]
          ]
        ],
        "type": "Polygon"
      }
    },
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "coordinates": [
          [
            [
              58,
              48
            ],
            [
              58,
              45
            ],
            [
              71,
              45
            ],
            [
              71,
              48
            ],
            [
              58,
              48
            ]
          ]
        ],
        "type": "Polygon"
      }
    }
  ]
}

Out:

{
	"type": "FeatureCollection",
	"features": [
		{
			"type": "Feature",
			"properties": {
				"stroke": "#080",
				"fill": "#080",
				"stroke-width": 6,
				"fill-opacity": 0.1
			},
			"geometry": {
				"coordinates": [
					[
						[
							60,
							47
						],
						[
							65,
							49
						],
						[
							70,
							46
						],
						[
							65,
							51
						],
						[
							60,
							47
						]
					]
				],
				"type": "Polygon"
			}
		},
		{
			"type": "Feature",
			"properties": {
				"stroke": "#F00",
				"fill": "#F00",
				"stroke-width": 6,
				"fill-opacity": 0.1
			},
			"geometry": {
				"type": "Polygon",
				"coordinates": [
					[
						[
							60,
							47
						],
						[
							62.5,
							48
						],
						[
							66.66666666666667,
							48
						],
						[
							70,
							46
						],
						[
							68,
							48
						],
						[
							61.25,
							48
						],
						[
							60,
							47
						]
					]
				]
			}
		},
		{
			"type": "Feature",
			"properties": {
				"stroke": "#00F",
				"fill": "#00F",
				"stroke-width": 3,
				"fill-opacity": 0.1
			},
			"geometry": {
				"coordinates": [
					[
						[
							58,
							48
						],
						[
							58,
							45
						],
						[
							71,
							45
						],
						[
							71,
							48
						],
						[
							58,
							48
						]
					]
				],
				"type": "Polygon"
			}
		}
	]
}

[stevage]

For completeness, the linestring case does behave correctly: