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https://github.com/nst/ShapefileReader
A shapefile reader in Swift
https://github.com/nst/ShapefileReader
Last synced: 3 months ago
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A shapefile reader in Swift
- Host: GitHub
- URL: https://github.com/nst/ShapefileReader
- Owner: nst
- License: mit
- Created: 2016-03-20T15:30:56.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2021-01-05T03:08:13.000Z (almost 4 years ago)
- Last Synced: 2024-05-31T21:01:49.241Z (6 months ago)
- Language: Swift
- Size: 6.02 MB
- Stars: 35
- Watchers: 10
- Forks: 20
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# ShapefileReader
__A shapefile reader in Swift__
__Description__
Reads data from files in [Shapefile](https://en.wikipedia.org/wiki/Shapefile) format.
__API Overview__
ShapefileReader is the only object you instantiate.
Internally, it builds the three following objects, depending on the available auxiliary files:
- `SHPReader` to read the shapes, ie the list of points
- `DBFReader` to read the data records associated with the shapes
- `SHXReader` to read the indices of the shapes, thus allowing direct access
Most usages of `ShapefileReader` will remain like:
```swift
guard let sr = ShapefileReader(path: "g1g15.shp") else { assertionFailure() }
// iterate over both shapes and records
for (shape, record) in sr.shapeAndRecordGenerator() {
// record is [AnyObject]
for points in shape.partPointsGenerator() {
// draw polygon with [CGPoint]
}
}
```
DBF API
```swift
// if dbf file exists
if let dbf = sr.dbf {
// number of records
let n = dbf.numberOfRecords
// fields description
print(dbf.fields)
// iterate over records
for r in dbf.recordGenerator() {
// ...
}
// access a record by index
print(dbf[1847])
}
```
[[DeletionFlag, C, 1, 0], [GMDNR, N, 9, 0], [GMDNAME, C, 50, 0], [BZNR, N, 9, 0], [KTNR, N, 9, 0], [GRNR, N, 9, 0], [AREA_HA, N, 9, 0], [X_MIN, N, 9, 0], [X_MAX, N, 9, 0], [Y_MIN, N, 9, 0], [Y_MAX, N, 9, 0], [X_CNTR, N, 9, 0], [Y_CNTR, N, 9, 0], [Z_MIN, N, 9, 0], [Z_MAX, N, 9, 0], [Z_AVG, N, 9, 0], [Z_MED, N, 9, 0], [Z_CNTR, N, 9, 0]]
[5586, Lausanne, 2225, 22, 1, 4138, 534438, 544978, 150655, 161554, 538200, 152400, 371, 930, 670, 666, 585]
SHX API
```swift
// if index file exists
if let shx = sr.shx {
// access a shape by index
if let offset = shx.shapeOffsetAtIndex(2) {
if let (nextIndex, shape) = shp.shapeAtOffset(offset) {
// use shape
}
}
}
```
or more simply
```swift
let shape = sr[2]
```
__Implementation Details__
- shape points are CGPoint arrays
- record are arrays of Int, Double, Bool or String (no NSDate, no optionals)
- random access in files and enumerators are used each time it is possible
- most of time, code will crash when files do not match the specs, feel free to open an issue an join the offending files
__Tests and Drawing__
The project comes with a unit test target.
Also, it comes with `BitmapCanvas` and its subclass `BitmapCanvasShapefile` which will generate the following PNG file.
You just need to change the path at the beginning of the `draw()` function in `main.swift` according the project's location.
__TODO__
Handle projection files, eg. from http://www.gadm.org/download.