1 #include <mbgl/geometry/dem_data.hpp>
2 #include <mbgl/math/clamp.hpp>
3
4 namespace mbgl {
5
DEMData(const PremultipliedImage & _image,Tileset::DEMEncoding encoding)6 DEMData::DEMData(const PremultipliedImage& _image, Tileset::DEMEncoding encoding):
7 dim(_image.size.height),
8 border(std::max<int32_t>(std::ceil(_image.size.height / 2), 1)),
9 stride(dim + 2 * border),
10 image({ static_cast<uint32_t>(stride), static_cast<uint32_t>(stride) }) {
11
12 if (_image.size.height != _image.size.width){
13 throw std::runtime_error("raster-dem tiles must be square.");
14 }
15
__anondc5c74880102(const uint8_t r, const uint8_t g, const uint8_t b)16 auto decodeMapbox = [] (const uint8_t r, const uint8_t g, const uint8_t b){
17 // https://www.mapbox.com/help/access-elevation-data/#mapbox-terrain-rgb
18 return (r * 256 * 256 + g * 256 + b)/10 - 10000;
19 };
20
__anondc5c74880202(const uint8_t r, const uint8_t g, const uint8_t b)21 auto decodeTerrarium = [] (const uint8_t r, const uint8_t g, const uint8_t b){
22 // https://aws.amazon.com/public-datasets/terrain/
23 return ((r * 256 + g + b / 256) - 32768);
24 };
25
26 auto decodeRGB = encoding == Tileset::DEMEncoding::Terrarium ? decodeTerrarium : decodeMapbox;
27
28 std::memset(image.data.get(), 0, image.bytes());
29
30 for (int32_t y = 0; y < dim; y++) {
31 for (int32_t x = 0; x < dim; x++) {
32 const int32_t i = y * dim + x;
33 const int32_t j = i * 4;
34 set(x, y, decodeRGB(_image.data[j], _image.data[j+1], _image.data[j+2]));
35 }
36 }
37
38 // in order to avoid flashing seams between tiles, here we are initially populating a 1px border of
39 // pixels around the image with the data of the nearest pixel from the image. this data is eventually
40 // replaced when the tile's neighboring tiles are loaded and the accurate data can be backfilled using
41 // DEMData#backfillBorder
42
43 for (int32_t x = 0; x < dim; x++) {
44 // left vertical border
45 set(-1, x, get(0, x));
46
47 // right vertical border
48 set(dim, x, get(dim - 1, x));
49
50 //left horizontal border
51 set(x, -1, get(x, 0));
52
53 // right horizontal border
54 set(x, dim, get(x, dim - 1));
55 }
56
57 // corners
58 set(-1, -1, get(0, 0));
59 set(dim, -1, get(dim - 1, 0));
60 set( -1, dim, get(0, dim - 1));
61 set(dim, dim, get(dim - 1, dim - 1));
62 }
63
64 // This function takes the DEMData from a neighboring tile and backfills the edge/corner
65 // data in order to create a one pixel "buffer" of image data around the tile. This is
66 // necessary because the hillshade formula calculates the dx/dz, dy/dz derivatives at each
67 // pixel of the tile by querying the 8 surrounding pixels, and if we don't have the pixel
68 // buffer we get seams at tile boundaries.
backfillBorder(const DEMData & borderTileData,int8_t dx,int8_t dy)69 void DEMData::backfillBorder(const DEMData& borderTileData, int8_t dx, int8_t dy) {
70 auto& o = borderTileData;
71
72 // Tiles from the same source should always be of the same dimensions.
73 assert(dim == o.dim);
74
75 // We determine the pixel range to backfill based which corner/edge `borderTileData`
76 // represents. For example, dx = -1, dy = -1 represents the upper left corner of the
77 // base tile, so we only need to backfill one pixel at coordinates (-1, -1) of the tile
78 // image.
79 int32_t _xMin = dx * dim;
80 int32_t _xMax = dx * dim + dim;
81 int32_t _yMin = dy * dim;
82 int32_t _yMax = dy * dim + dim;
83
84 if (dx == -1) _xMin = _xMax - 1;
85 else if (dx == 1) _xMax = _xMin + 1;
86
87 if (dy == -1) _yMin = _yMax - 1;
88 else if (dy == 1) _yMax = _yMin + 1;
89
90 int32_t xMin = util::clamp(_xMin, -border, dim + border);
91 int32_t xMax = util::clamp(_xMax, -border, dim + border);
92
93 int32_t yMin = util::clamp(_yMin, -border, dim + border);
94 int32_t yMax = util::clamp(_yMax, -border, dim + border);
95
96 int32_t ox = -dx * dim;
97 int32_t oy = -dy * dim;
98
99 for (int32_t y = yMin; y < yMax; y++) {
100 for (int32_t x = xMin; x < xMax; x++) {
101 set(x, y, o.get(x + ox, y + oy));
102 }
103 }
104 }
105
106 } // namespace mbgl
107