# gdalcompare.py

Compare two images.

## Synopsis

    gdalcompare.py [--help] [--help-general]
                   [-dumpdiffs] [-skip_binary] [-skip_overviews]
                   [-skip_geolocation] [-skip_geotransform]
                   [-skip_metadata] [-skip_rpc] [-skip_srs]
                   [-sds] <golden_file> <new_file>

## Description

The gdalcompare.py script compares two GDAL supported datasets and reports the differences. In addition to reporting differences to the standard output the script will also return the difference count in its exit value.

Image pixels, and various metadata are checked. There is also a byte by byte comparison done which will count as one difference. So if it is only important that the GDAL visible data is identical a difference count of 1 (the binary difference) should be considered acceptable.

--help

  Show this help message and exit

--help-general

  Gives a brief usage message for the generic GDAL commandline options and exit.

-dumpdiffs

  New in version 3.8.

  Whether to output the difference in pixel content in a TIFF file in the current directory.

-skip_binary

  New in version 3.8.

  Whether to skip exact comparison of binary content.

-skip_overviews

  New in version 3.8.

  Whether to skip comparison of overviews.

-skip_geolocation

  New in version 3.8.

  Whether to skip comparison of GEOLOCATION metadata domain.

-skip_geotransform

  New in version 3.8.

  Whether to skip comparison of geotransform matrix.

-skip_metadata

  New in version 3.8.

  Whether to skip comparison of metadata

-skip_rpc

  New in version 3.8.

  Whether to skip comparison of Rational Polynomial Coefficients (RPC) metadata domain.

-skip_srs

  New in version 3.8.

  Whether to skip comparison of spatial reference systems (SRS).

-sds

  If this flag is passed the script will compare all subdatasets that are part of the dataset, otherwise subdatasets are ignored.

<golden_file>

  The file that is considered correct, referred to as the golden file.

<new_file>

  The file being compared to the golden file, referred to as the new file.

Note that the gdalcompare.py script (like all the other scripts) can also be called as a library from python code: from osgeo_utils import gdalcompare. The primary entry point is gdalcompare.compare_db() which takes a golden gdal.Dataset and a new gdal.Dataset as arguments and returns a difference count (excluding the binary comparison). The gdalcompare.compare_sds() entry point can be used to compare subdatasets.

## Examples

    gdalcompare.py -dumpdiffs N.tiff S.tiff; echo $?
    Files differ at the binary level.
    Band 1 checksum difference:
      Golden: 36694
      New:    40645
      Pixels Differing: 1509
      Maximum Pixel Difference: 255.0
      Wrote Diffs to: 1.tif
    Differences Found: 2
    2

    gdalcompare.py N.tiff N.tiff; echo $?
    Differences Found: 0
    0