GeoExpress enables you to "tile out" an existing MrSID or JPEG 2000 image into a number of smaller output tiles, including GeoTIFF images. The operation is called "demosaicking" because its result is the opposite of the result of the mosaicking process. However, the input image for a demosaicking operation does not have to be the result of any previous mosaicking.
To demosaic an existing MrSID or JPEG 2000 file, use the -outputtilegrid/-otg switch with the number of rows and columns that you wish to split the image into.
For example:
mrsidgeoencoder -i foo.sid -o foo2.sid -outputtilegrid 2 3
This example splits the source image into two rows and three columns. The result will be 12 new image tiles. For information about the name and position of each tile, see Output Tiling and File Names.
If you define a crop region – either via a vector overlay or by setting crop commands – the grid pertains only to the crop region. By default the crop region is the entire image.
The -outputtilemag/-otm switch enables you to set the magnification or scale of the output tiles. A magnification of 1.0 represents the image at full scale, while a magnification of 0.5 reduces the output dimensions by half.
For example, if your input image measures 1000 x 1200 pixels and you set the output tiling to 2 rows, 2 columns and a magnification of 1, the result would be four tiles that measure 500 x 600 pixels each.
mrsidgeoencoder -i foo.sid -o foo2.sid -otg 2 2 -outputtilemag 1
If on the same 1000 x 1200 pixel image you set the output tiling to 2 rows, 2 columns and a magnification of 0.5, the result would be four tiles that measure 250 x 300 pixels each, half the size they would be at full magnification.
mrsidgeoencoder -i foo.sid -o foo2.sid -otg 2 2 -otm 0.5
Allowed values are fractional numbers greater than zero and less than or equal to 1. The default magnification value is 1.
The name of each output tile will have the row and column value (starting at zero) appended to the base output name as follows:
<base name>_<row>_<column>.<file extension>
For example, if you specify 2 rows and 3 columns and a "base" file name of "novato.sid", then the resulting output files will be named and positioned as follows:
novato_0_0.sid (row 0, column 0)novato_0_1.sid
(row 0, column 1)novato_0_2.sid
(row 0, column 2)novato_1_0.sid
(row 1, column 0)novato_1_1.sid
(row 1, column 1)novato_1_2.sid (row 1, column 2)