# Examples

## Getting information on a raster dataset using dedicated methods

The following snippet uses individual API methods to retrieve characters of a GDAL raster dataset and its bands.

    from osgeo import gdal
    import json

    gdal.UseExceptions()

    ds = gdal.Open("data/byte.tif")
    print(f"Width: {ds.RasterXSize}")
    print(f"Height: {ds.RasterYSize}")
    print(f"Number of bands: {ds.RasterCount}")

    ---------------------------------------------------------------------------
    ImportError                               Traceback (most recent call last)
    Cell In[1], line 1
    ----> 1 from osgeo import gdal
          2 import json
          4 gdal.UseExceptions()

    ImportError: cannot import name 'gdal' from 'osgeo' (unknown location)

    srs = ds.GetSpatialRef()
    srs_unit = ""
    if srs:
        srs_as_projjson = json.loads(srs.ExportToPROJJSON())
        print("SRS:")
        srs_type = srs_as_projjson["type"]
        print(f"  Type: {srs_type}")
        name = srs_as_projjson["name"]
        print(f"  Name: {name}")
        if "id" in srs_as_projjson:
            id = srs_as_projjson["id"]
            authority = id["authority"]
            code = id["code"]
            print(f"  Id: {authority}:{code}")
        srs_unit = " " + srs_as_projjson["coordinate_system"]["axis"][0]["unit"]

    geotransform = ds.GetGeoTransform()
    if geotransform[2] == 0 and geotransform[4] == 0:
        print(f"Upper-left corner georeferenced position: X={geotransform[0]}{srs_unit}, Y={geotransform[3]}{srs_unit}")
        print(f"Horizontal resolution: {geotransform[1]}{srs_unit}")
        print(f"Vertical resolution: {geotransform[5]}{srs_unit} (negative value indicates a north-up image)")
    else:
        print(f"Geotransformation matrix: {geotransform}")
    print(f"Metadata: {ds.GetMetadata()}")

    for idx, band in enumerate(ds):
        print(f"Band {idx+1}:")
        print(f"  Data type: {gdal.GetDataTypeName(band.DataType)}")
        block_width, block_height = band.GetBlockSize()
        print(f"  Block width: {block_width}")
        print(f"  Block height: {block_height}")
        print(f"  Metadata: {band.GetMetadata()}")

    # Explicitly close the dataset. May be needed in creation/update scenarios, to
    # make sure all data is properly flushed to storage, or even in read-only
    # scenarios, if you want to delete the file afterwards (on Windows).
    # You may also use a context manager with "with gdal.Open(...) as ds" as shown
    # in later examples.
    ds.Close()

## Getting information on a raster dataset using gdal.Info()

The following snippet uses the `osgeo.gdal.Info()` method to retrieve characters of a GDAL raster dataset and its bands, as a JSON document.

    from osgeo import gdal
    import pprint

    gdal.UseExceptions()

    with gdal.Open("data/byte.tif") as ds:
        info = gdal.Info(ds, format='json')
        del info["stac"]  # to avoid cluttering below output
        pprint.pprint(info, indent=2, width=100)

## Reading a whole raster as a numpy array

The following snippet uses the `osgeo.gdal.Dataset.ReadAsArray()` method to retrieve the pixel values of all the bands of a dataset as a numpy array.

A 2D array is returned for a single band image. A 3D array, with first dimension being the band one, is returned for images with multiple bands.

    from osgeo import gdal

    gdal.UseExceptions()

    with gdal.Open("data/byte.tif") as ds:
        array = ds.ReadAsArray()
        print(array)