Hide keyboard shortcuts

Hot-keys on this page

r m x p   toggle line displays

j k   next/prev highlighted chunk

0   (zero) top of page

1   (one) first highlighted chunk

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

335

336

337

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

370

371

372

373

# 

# LSST Data Management System 

# Copyright 2008, 2009, 2010 LSST Corporation. 

# 

# This product includes software developed by the 

# LSST Project (http://www.lsst.org/). 

# 

# This program is free software: you can redistribute it and/or modify 

# it under the terms of the GNU General Public License as published by 

# the Free Software Foundation, either version 3 of the License, or 

# (at your option) any later version. 

# 

# This program is distributed in the hope that it will be useful, 

# but WITHOUT ANY WARRANTY; without even the implied warranty of 

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 

# GNU General Public License for more details. 

# 

# You should have received a copy of the LSST License Statement and 

# the GNU General Public License along with this program. If not, 

# see <http://www.lsstcorp.org/LegalNotices/>. 

# 

import numbers 

 

import lsst.pex.exceptions 

import lsst.afw.geom as afwGeom 

from lsst.sphgeom import ConvexPolygon 

 

from .patchInfo import PatchInfo, makeSkyPolygonFromBBox 

 

__all__ = ["TractInfo"] 

 

 

class TractInfo: 

"""Information about a tract in a SkyMap sky pixelization 

 

The tract is subdivided into rectangular patches. Each patch has the following properties: 

- An inner region defined by an inner bounding. The inner regions of the patches exactly tile the tract, 

and all inner regions have the same dimensions. The tract is made larger as required to make this work. 

- An outer region defined by an outer bounding box. The outer region extends beyond the inner region 

by patchBorder pixels in all directions, except there is no border at the edges of the tract. 

Thus patches overlap each other but never extend off the tract. If you do not want any overlap 

between adjacent patches then set patchBorder to 0. 

- An index that consists of a pair of integers: 

0 <= x index < numPatches[0] 

0 <= y index < numPatches[1] 

Patch 0,0 is at the minimum corner of the tract bounding box. 

""" 

 

def __init__(self, id, patchInnerDimensions, patchBorder, ctrCoord, vertexCoordList, tractOverlap, wcs): 

"""Construct a TractInfo 

 

@param[in] id: tract ID 

@param[in] patchInnerDimensions: dimensions of inner region of patches (x,y pixels) 

@param[in] patchBorder: overlap between adjacent patches (in pixels, one int) 

@param[in] ctrCoord: ICRS sky coordinate of center of inner region of tract 

as an lsst.afw.geom.SpherePoint; also used as the CRVAL for the WCS. 

@param[in] vertexCoordList: list of ICRS sky coordinates (lsst.afw.geom.SpherePoint) 

of vertices that define the boundaries of the inner region 

@param[in] tractOverlap: minimum overlap between adjacent sky tracts; an afwGeom.Angle; 

this defines the minimum distance the tract extends beyond the inner region in all directions 

@param[in,out] wcs: an afwImage.Wcs; the reference pixel will be shifted as required 

so that the lower left-hand pixel (index 0,0) has pixel position 0.0, 0.0 

 

@warning 

- It is not enforced that ctrCoord is the center of vertexCoordList, but SkyMap relies on it 

""" 

self._id = id 

try: 

assert len(patchInnerDimensions) == 2 

self._patchInnerDimensions = afwGeom.Extent2I(*(int(val) for val in patchInnerDimensions)) 

except Exception: 

raise TypeError("patchInnerDimensions=%s; must be two ints" % (patchInnerDimensions,)) 

self._patchBorder = int(patchBorder) 

self._ctrCoord = ctrCoord 

self._vertexCoordList = tuple(vertexCoordList) 

self._tractOverlap = tractOverlap 

 

minBBox = self._minimumBoundingBox(wcs) 

initialBBox, self._numPatches = self._setupPatches(minBBox, wcs) 

self._bbox, self._wcs = self._finalOrientation(initialBBox, wcs) 

 

def _minimumBoundingBox(self, wcs): 

"""Calculate the minimum bounding box for the tract, given the WCS 

 

The bounding box is created in the frame of the supplied WCS, 

so that it's OK if the coordinates are negative. 

 

We compute the bounding box that holds all the vertices and the 

desired overlap. 

""" 

minBBoxD = afwGeom.Box2D() 

halfOverlap = self._tractOverlap / 2.0 

for vertexCoord in self._vertexCoordList: 

if self._tractOverlap == 0: 

minBBoxD.include(wcs.skyToPixel(vertexCoord)) 

else: 

numAngles = 24 

angleIncr = afwGeom.Angle(360.0, afwGeom.degrees) / float(numAngles) 

for i in range(numAngles): 

offAngle = angleIncr * i 

offCoord = vertexCoord.offset(offAngle, halfOverlap) 

pixPos = wcs.skyToPixel(offCoord) 

minBBoxD.include(pixPos) 

return minBBoxD 

 

def _setupPatches(self, minBBox, wcs): 

"""Setup for patches of a particular size. 

 

We grow the bounding box to hold an exact multiple of 

the desired size (patchInnerDimensions), while keeping 

the center roughly the same. We return the final 

bounding box, and the number of patches in each dimension 

(as an Extent2I). 

 

@param minBBox Minimum bounding box for tract 

@param wcs Wcs object 

@return final bounding box, number of patches 

""" 

bbox = afwGeom.Box2I(minBBox) 

bboxMin = bbox.getMin() 

bboxDim = bbox.getDimensions() 

numPatches = afwGeom.Extent2I(0, 0) 

for i, innerDim in enumerate(self._patchInnerDimensions): 

num = (bboxDim[i] + innerDim - 1) // innerDim # round up 

deltaDim = (innerDim * num) - bboxDim[i] 

if deltaDim > 0: 

bboxDim[i] = innerDim * num 

bboxMin[i] -= deltaDim // 2 

numPatches[i] = num 

bbox = afwGeom.Box2I(bboxMin, bboxDim) 

return bbox, numPatches 

 

def _finalOrientation(self, bbox, wcs): 

"""Determine the final orientation 

 

We offset everything so the lower-left corner is at 0,0 

and compute the final Wcs. 

 

@param bbox Current bounding box 

@param wcs Current Wcs 

@return revised bounding box, revised Wcs 

""" 

finalBBox = afwGeom.Box2I(afwGeom.Point2I(0, 0), bbox.getDimensions()) 

# shift the WCS by the same amount as the bbox; extra code is required 

# because simply subtracting makes an Extent2I 

pixPosOffset = afwGeom.Extent2D(finalBBox.getMinX() - bbox.getMinX(), 

finalBBox.getMinY() - bbox.getMinY()) 

wcs = wcs.copyAtShiftedPixelOrigin(pixPosOffset) 

return finalBBox, wcs 

 

def getSequentialPatchIndex(self, patchInfo): 

"""Return a single integer that uniquely identifies the given patch 

within this tract. 

""" 

x, y = patchInfo.getIndex() 

nx, ny = self.getNumPatches() 

return nx*y + x 

 

def getPatchIndexPair(self, sequentialIndex): 

nx, ny = self.getNumPatches() 

x = sequentialIndex % nx 

y = (sequentialIndex - x) / nx 

return (x, y) 

 

def findPatch(self, coord): 

"""Find the patch containing the specified coord 

 

@param[in] coord: ICRS sky coordinate (lsst.afw.geom.SpherePoint) 

@return PatchInfo of patch whose inner bbox contains the specified coord 

 

@raise LookupError if coord is not in tract or we cannot determine the 

pixel coordinate (which likely means the coord is off the tract). 

 

@note This routine will be more efficient if coord is ICRS. 

""" 

try: 

pixel = self.getWcs().skyToPixel(coord) 

except (lsst.pex.exceptions.DomainError, lsst.pex.exceptions.RuntimeError): 

# Point must be way off the tract 

raise LookupError("Unable to determine pixel position for coordinate %s" % (coord,)) 

pixelInd = afwGeom.Point2I(pixel) 

if not self.getBBox().contains(pixelInd): 

raise LookupError("coord %s is not in tract %s" % (coord, self.getId())) 

patchInd = tuple(int(pixelInd[i]/self._patchInnerDimensions[i]) for i in range(2)) 

return self.getPatchInfo(patchInd) 

 

def findPatchList(self, coordList): 

"""Find patches containing the specified list of coords 

 

@param[in] coordList: list of sky coordinates (lsst.afw.geom.SpherePoint) 

@return list of PatchInfo for patches that contain, or may contain, the specified region. 

The list will be empty if there is no overlap. 

 

@warning: 

* This may give incorrect answers on regions that are larger than a tract 

* This uses a naive algorithm that may find some patches that do not overlap the region 

(especially if the region is not a rectangle aligned along patch x,y). 

""" 

box2D = afwGeom.Box2D() 

for coord in coordList: 

try: 

pixelPos = self.getWcs().skyToPixel(coord) 

except (lsst.pex.exceptions.DomainError, lsst.pex.exceptions.RuntimeError): 

# the point is so far off the tract that its pixel position cannot be computed 

continue 

box2D.include(pixelPos) 

bbox = afwGeom.Box2I(box2D) 

bbox.grow(self.getPatchBorder()) 

bbox.clip(self.getBBox()) 

if bbox.isEmpty(): 

return () 

 

llPatchInd = tuple(int(bbox.getMin()[i]/self._patchInnerDimensions[i]) for i in range(2)) 

urPatchInd = tuple(int(bbox.getMax()[i]/self._patchInnerDimensions[i]) for i in range(2)) 

return tuple(self.getPatchInfo((xInd, yInd)) 

for xInd in range(llPatchInd[0], urPatchInd[0]+1) 

for yInd in range(llPatchInd[1], urPatchInd[1]+1)) 

 

def getBBox(self): 

"""Get bounding box of tract (as an afwGeom.Box2I) 

""" 

return afwGeom.Box2I(self._bbox) 

 

def getCtrCoord(self): 

"""Get ICRS sky coordinate of center of tract (as an lsst.afw.geom.SpherePoint) 

""" 

return self._ctrCoord 

 

def getId(self): 

"""Get ID of tract 

""" 

return self._id 

 

def getNumPatches(self): 

"""Get the number of patches in x, y 

 

@return the number of patches in x, y 

""" 

return self._numPatches 

 

def getPatchBorder(self): 

"""Get batch border 

 

@return patch border (pixels) 

""" 

return self._patchBorder 

 

def getPatchInfo(self, index): 

"""Return information for the specified patch 

 

@param[in] index: index of patch, as a pair of ints, 

or a sequential index as returned by getSequentialPatchIndex; 

negative values are not supported. 

@return patch info, an instance of PatchInfo 

 

@raise IndexError if index is out of range 

""" 

if isinstance(index, numbers.Number): 

index = self.getPatchIndexPair(index) 

if (not 0 <= index[0] < self._numPatches[0]) \ 

or (not 0 <= index[1] < self._numPatches[1]): 

raise IndexError("Patch index %s is not in range [0-%d, 0-%d]" % 

(index, self._numPatches[0]-1, self._numPatches[1]-1)) 

innerMin = afwGeom.Point2I(*[index[i] * self._patchInnerDimensions[i] for i in range(2)]) 

innerBBox = afwGeom.Box2I(innerMin, self._patchInnerDimensions) 

if not self._bbox.contains(innerBBox): 

raise RuntimeError( 

"Bug: patch index %s valid but inner bbox=%s not contained in tract bbox=%s" % 

(index, innerBBox, self._bbox)) 

outerBBox = afwGeom.Box2I(innerBBox) 

outerBBox.grow(self.getPatchBorder()) 

outerBBox.clip(self._bbox) 

return PatchInfo( 

index=index, 

innerBBox=innerBBox, 

outerBBox=outerBBox, 

) 

 

def getPatchInnerDimensions(self): 

"""Get dimensions of inner region of the patches (all are the same) 

 

@return dimensions of inner region of the patches (as an afwGeom Extent2I) 

""" 

return self._patchInnerDimensions 

 

def getTractOverlap(self): 

"""Get minimum overlap of adjacent sky tracts 

 

@return minimum overlap between adjacent sky tracts, as an afwGeom Angle 

""" 

return self._tractOverlap 

 

def getVertexList(self): 

"""Get list of sky coordinates of vertices that define the boundary of the inner region 

 

@warning: this is not a deep copy 

""" 

return self._vertexCoordList 

 

def getInnerSkyPolygon(self): 

"""Get inner on-sky region as a sphgeom.ConvexPolygon. 

""" 

skyUnitVectors = [sp.getVector() for sp in self.getVertexList()] 

return ConvexPolygon.convexHull(skyUnitVectors) 

 

def getOuterSkyPolygon(self): 

"""Get outer on-sky region as a sphgeom.ConvexPolygon 

""" 

return makeSkyPolygonFromBBox(bbox=self.getBBox(), wcs=self.getWcs()) 

 

def getWcs(self): 

"""Get WCS of tract 

 

@warning: this is not a deep copy 

""" 

return self._wcs 

 

def __str__(self): 

return "TractInfo(id=%s)" % (self._id,) 

 

def __repr__(self): 

return "TractInfo(id=%s, ctrCoord=%s)" % (self._id, self._ctrCoord.getVector()) 

 

def __iter__(self): 

xNum, yNum = self.getNumPatches() 

for y in range(yNum): 

for x in range(xNum): 

yield self.getPatchInfo((x, y)) 

 

def __len__(self): 

xNum, yNum = self.getNumPatches() 

return xNum*yNum 

 

def __getitem__(self, index): 

return self.getPatchInfo(index) 

 

def contains(self, coord): 

"""Does this tract contain the coordinate?""" 

try: 

pixels = self.getWcs().skyToPixel(coord) 

except (lsst.pex.exceptions.DomainError, lsst.pex.exceptions.RuntimeError): 

# Point must be way off the tract 

return False 

return self.getBBox().contains(afwGeom.Point2I(pixels)) 

 

 

class ExplicitTractInfo(TractInfo): 

"""Information for a tract specified explicitly 

 

A tract is placed at the explicitly defined coordinates, with the nominated 

radius. The tracts are square (i.e., the radius is really a half-size). 

""" 

 

def __init__(self, ident, patchInnerDimensions, patchBorder, ctrCoord, radius, tractOverlap, wcs): 

# We don't want TractInfo setting the bbox on the basis of vertices, but on the radius. 

vertexList = [] 

self._radius = radius 

super(ExplicitTractInfo, self).__init__(ident, patchInnerDimensions, patchBorder, ctrCoord, 

vertexList, tractOverlap, wcs) 

# Shrink the box slightly to make sure the vertices are in the tract 

bboxD = afwGeom.BoxD(self.getBBox()) 

bboxD.grow(-0.001) 

finalWcs = self.getWcs() 

self._vertexCoordList = finalWcs.pixelToSky(bboxD.getCorners()) 

 

def _minimumBoundingBox(self, wcs): 

"""The minimum bounding box is calculated using the nominated radius""" 

bbox = afwGeom.Box2D() 

for i in range(4): 

cornerCoord = self._ctrCoord.offset(i*90*afwGeom.degrees, self._radius + self._tractOverlap) 

pixPos = wcs.skyToPixel(cornerCoord) 

bbox.include(pixPos) 

return bbox