georesize

Resize geographic raster

Since R2019a

Syntax

[B,RB] = georesize(A,RA,scale)

[B,RB] = georesize(A,RA,latscale,lonscale)

[B,RB] = georesize(___,method)

[B,RB] = georesize(___,'Antialiasing',TF)

Description

[B,RB] = georesize(A,RA,scale) returns the raster B that is scale times the size of the raster A. RA is a geographic raster reference object that specifies the location and extent of data in A. georesize returns the raster reference object RB that is associated with the returned raster B. By default, georesize uses cubic interpolation.

georesize preserves the limits of the raster. If the scale specified divides evenly into the numbers of cells in each dimension, or the number of samples in each dimension minus 1, the limits of the output are the same as the input. Otherwise, georesize adjusts the output limits by a fraction of the cell extents or sample spacing values.

[B,RB] = georesize(A,RA,latscale,lonscale) returns the raster B that is latscale times the size of A in column (north-south) direction and lonscale times the size of A in the row (east-west) direction.

[B,RB] = georesize(___,method) returns a resized raster where method specifies the interpolation method.

[B,RB] = georesize(___,'Antialiasing',TF) specifies whether to perform antialiasing when shrinking a raster. The default depends on the type of interpolation. For nearest-neighbor interpolation, the default value is false. For all other interpolation methods, the default is true.

Examples

Resize Geographic Raster

Import a sample geographic raster and geographic cells reference object.

[Z,R] = readgeoraster('raster_sample2.tif');

Resize the raster using georesize. Double the length and width of the raster by specifying the scale as 2. Use nearest neighbor interpolation by specifying the interpolation method as 'nearest'.

[Z2,R2] = georesize(Z,R,2,'nearest');

You can also resize the input raster by specifying different scales for the north-south and east-west directions.

[Z3,R3] = georesize(Z,R,3,2,'nearest');
R3.RasterSize

ans = 1×2

     6     4

Verify the raster has been resized by comparing the size of the original raster with the size of the updated rasters.

R.RasterSize

ans = 1×2

     2     2

R2.RasterSize

ans = 1×2

     4     4

R3.RasterSize

ans = 1×2

     6     4

If the rasters are small, you can compare them directly.

Z

Z = 2×2

     1     2
     3     4

Z2

Z2 = 4×4

     1     1     2     2
     1     1     2     2
     3     3     4     4
     3     3     4     4

Z3

Z3 = 6×4

     1     1     2     2
     1     1     2     2
     1     1     2     2
     3     3     4     4
     3     3     4     4
     3     3     4     4

Resize Geographic Raster Data Set

Load a raster data set showing land elevations and bathymetry for the region around the Korean peninsula, at a resolution of 12 cells per degree. The data includes a raster image, korea5c, and an associated geographic raster reference object, korea5cR.

load korea5c

View the raster data set, using geoshow, specifying the associated raster reference object.

geoshow(korea5c,korea5cR,'DisplayType','texturemap')

Resize the raster to be a quarter of its original size.

[resizedKorea,resizedKoreaR] = georesize(korea5c,korea5cR,0.25);

View the resized raster. Note that geoshow preserves the original limits of the map in the display so that, at first glance, the resized raster appears to be the same size as the original. A closer look reveals that the size of pixels in the resized raster are larger than the pixels in the original.

figure
geoshow(resizedKorea,resizedKoreaR,'DisplayType','texturemap')

Input Arguments

A — Raster to be resized

numeric or logical array

Raster to be resized, specified as a numeric or logical array. If A has more than two dimensions, such as with a color raster in RGB format, georesize only resizes the first two dimensions.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical

RA — Information about location and extent of raster

raster reference object

Information about location and extent of raster, specified as a raster reference object. To convert a referencing vector or referencing matrix into a raster reference object, use the refvecToGeoRasterReference or refmatToGeoRasterReference.

scale — Amount of resizing

numeric scalar

Amount of resizing, specified as numeric scalar. If scale is in the range [0 1], B is smaller than A. If scale is greater than 1, B is larger than A.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

latscale — Amount of resizing in north-south direction

numeric scalar

Amount of resizing in north-south direction, specified as numeric scalar. If latscale is in the range [0 1], B is smaller than A. If latscale is greater than 1, B is larger than A.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

lonscale — Amount of resizing in east-west direction

numeric scalar

Amount of resizing in east-west direction, specified as numeric scalar. If lonscale is in the range [0 1], B is smaller than A. If lonscale is greater than 1, B is larger than A.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

method — Interpolation method

'cubic' (default) | 'nearest' | 'bilinear'

Interpolation method, specified as one of the following values:

Value	Description
'nearest'	Nearest-neighbor interpolation
'bilinear'	Bilinear interpolation
'cubic'	Cubic interpolation

Data Types: char | string

Output Arguments

B — Resized raster

numeric or logical array

Resized raster, returned as a numeric or logical array.

RB — Information about location and extent of raster

geographic raster reference object

Information about location and extent of the raster, returned as a geographic raster reference object.

Tips

• Use georesize with raster data in latitude and longitude coordinates. To work with projected raster data, in x- and y-coordinates, use mapresize.

Version History

Introduced in R2019a